T&DI Congress 2011: Integrated Transportation and Development for a Better Tomorrow

Several decades ago and not long after developed countries, the developing world also recognized the need for the availability of road asset data. However, systematic data collection, establishment of databases and creation of management systems has been failing because of poorly developed networks requiring expansion and modernization, as well as a lack of funding, equipment and staff. The former Yugoslavia, once a leader in the Balkans, began to develop a data collection methodology and to create a road database in the late 1980's; however, the subsequent conflicts brought most of these activities to a halt. There was a marked discrepancy between the levels of achievement in the different parts of the former federal state, although the activities commenced at the same time, with equal resources allocated for the purpose. In this paper, the authors present the latest developments and their experiences gained in three former Yugoslav republics (Bosnia and Herzegovina, Serbia and Macedonia), clearly demonstrating the problems and challenges faced by their local road management agencies, as well as lessons learned from the projects in which they participated.

Pavement condition data are either continuously collected or sampled. In sampling it is assumed that the time and costs of data collection can be reduced and the pavement condition of shorter segments represent the conditions of larger sections. In a study sponsored by the Federal Highway Administration, pavement distress data along several miles of roads were obtained from four State Highway Agencies. Each department collects and stores distress data on a continuous basis for each 0.1 mile section along the network. The continuous data were sampled and the impacts on the accuracy of pavement decisions were analyzed. Results of the analyses are discussed herein. It is shown that, for variable pavement conditions, ten percent sampling leads to inaccurate decisions. Pavement sections in need of repair are ignored whereas healthy sections are selected for repair. The costs incurred due to inaccurate decisions could be much higher than the saving incurred by sampling.

A critical component of runway pavement survey is visual inspection of surface conditions. The dominant practice today is still based on manual survey, which causes delays, poses safety hazard, labor intensive and error-prone. In recent years, Hartsfield-Jackson Atlanta International Airport (HJAIA) has been using digital imaging technology to acquire pavement images for condition survey purposes. Initially, 3-mm resolution digital technology was used. In the most recent iteration, the developer used 1-mm technology and laser imaging to cover entire runway pavements. In this paper, the authors introduce data collection techniques on lasers and imaging. The laser based imaging system works day or night without shadowing problem or the impact of sun light. A vehicle is used to collect 14-ft wide continuous images of a runway at highway speed. A methodology is used to stitch images of multiple data collection runs for the same runway, so that a single uniform virtual imagery is formed for one entire runway. GPS coordinates are also established for multiple points on the images. A procedure to conduct Pavement Condition Index (PCI) evaluation on runway pavement is presented. Tests are conducted to demonstrate that this methodology is superior to manual approach. Condition survey of runways based on the 1-mm images can be substantially more accurate and effective than any manual approach.

Maintenance and rehabilitation strategies are critical components of a pavement management system. The on-time and effective rehabilitation not only improves the pavement performance, but also prolongs the service life of an existing pavement. The process to select feasible rehabilitation alternatives from a pool of available alternatives for pavement rehabilitation can range from using simple judgment to relying on a decision tree based expert system. However, the process of knowledge retrieval in an expert system is tedious and rule revision is not convenient. Therefore, a new technique called Case-Based Reasoning (CBR) is used in this paper to reduce the complexity of the problem solving process by relying on solution parameters that were successfully applied in the previous similar problems. The solution parameters are contained in an active case base that is continually updated with new solution parameters when new problems are solved. In this paper, a CBR system is proposed for determining pavement rehabilitation strategies by comparing the similarity between available solutions and new solutions.

The Gateway Traveler Information System (Gateway) and www.travelmidwest.com web site (formerly www.gcmtravel.com) provide timely, accurate, and useful traffic information to a variety of public and private constituents. Recurring and nonrecurring congestion directly impacts the economy, the environment, and the safety of the transportation network. The services and data provided by the Gateway have become a mission-critical service of the Illinois Department of Transportation (IDOT) and the geographically-connected roadway operators that are members of the Lake Michigan Interstate Gateway Alliance (LMIGA). This paper details the background and history of LMIGA and the Gateway, specifically www.travelmidwest.com. It highlights the goals of the Gateway and identifies four challenges and the associated resolutions that IDOT and the LMIGA partners use to ensure the Gateway is able to maximize the dissemination of quality traveler information to the staffs of operating agencies, the traveling public, and third party data subscribers. This paper also describes the elements that will impact both the system and the regional partnership as technologies advance, traveler information demands increase, and policies evolve.

The California High Speed Rail project is an 800 mile long high speed rail network that will ultimately connect the cities of Los Angeles, San Francisco, Sacramento and San Diego. Phase I of the project will connect Los Angles to San Francisco through the Central Valley; Phase II will add connections to Sacramento and San Diego completing the overall system. Phase I is divided into eight sections including Palmdale to Los Angeles, Arup is a part of a joint venture team with Hatch Mott Macdonald (HMM) and URS to develop 30% design drawings to certify the Environment Impact Report/ Environmental Impact Statement (EIR/EIS) and to provide a basis for contractors to submit bids for construction. Palmdale to Los Angeles has two distinct sections including Palmdale to Sylmar which passes through rural and suburban cities with terrain ranging from flat lands to mountainous and Sylmar to Los Angeles Union Station (LAUS) which passes through a densely populated mixture of urban and suburban cities in the San Fernando Valley adjacent to the Los Angeles River. Particular challenges are faced when designing a high speed rail corridor with design speeds reaching 220 miles per hour (mph) through a dense urban suburban core such as in the Sylmar to LAUS section of the project. The paper will discuss the criteria used to design the rail alignment, the challenges and constraints encountered along the route and the construction methods employed to mitigate the constraints.

This paper proposes use of median travel time compared to mean travel time as the measure of central tendency to calculate Buffer Time Index (BTI), one of the most important measures of travel time reliability. This study examined gamma, exponential, largest extreme value, smallest extreme value, logistic, Weibull, lognormal and log-logistic distributions to determine the best fit to travel time data for two cases: 24 hours and peak hours for a highway with Variable Speed Limit (VSL) conditions. The goodness-of-fit tests indicated that the log-normal distribution best represented the travel time data for peak periods and log-logistic distribution better fitted the travel time data for 24 hours. The log-logistic distribution and log-normal distributions were positively skewed and for skewed distributions, median is the best estimate of central tendency. Hence, median travel time is proposed for calculating BTI. The difference in values of BTIs were evaluated when mean and median travel time were used. Travelers must add extra time to their average travel time to ensure on-time arrival. It was found that this extra time increases from 11% to 30% when median travel time is used as the average travel time compared to mean travel time for calculation of BTI.

This paper presents the systematic evaluation of Variable Speed Limit (VSL) system implemented on I-270 in St. Louis County. The system varies the speed limit in real time during periods of recurring and non-recurring congestion to prevent traffic from breaking down. The system was evaluated objectively and subjectively, and this paper describes the objective evaluation of the system. The objective evaluation was performed by comparing the traffic flow parameters during static speed limit (pre-VSL) with variable speed limit (post-VSL) by using five measures of performance: 1) speed, 2) volume, 3) occupancy, 4) travel time, and 5) congestion measures. Identification of congested segments and the time periods for the analyses were the initial steps for evaluating the system. Traffic data were provided by MoDOT collected using Remote Traffic Microwave Sensors. Average speed, volume and time occupancy profiles indicated that the VSL system change in traffic conditions including congestion. Preventing the highway from reaching its capacity and avoiding the traffic breakdown is one of the main objectives of VSL system initiation. It can be achieved by upstream drivers reducing speed, metering the upstream traffic and preventing traffic from breaking down. Congestion measures evaluation indicates change in Travel Time, Percentage of Congested Travel and reduction in duration, extent and intensity of congestion. The VSL system benefits were determined, which indicated that the system benefits will pay for the initial capital cost of the system over the years. This study can be used by Departments of Transportation for evaluation of active management systems.

Micro unmanned aerial vehicles (MUAVs) that are equipped with digital imaging systems and Global Positioning System (GPS) provide a potential opportunity for improving the effectiveness and safety of roadside condition and inventory surveys. This paper provides an assessment of the effectiveness of MUAVs as a tool for collecting condition and inventory data for roadside infrastructure assets using a field experiment. The field experiment entails performing a level of service (LOS) condition assessment on 10 roadway sample units on IH-20 in Tyler, Texas. The condition of these sample units was assessed twice: onsite (i.e., ground truth) and by observing digital images (still and video) collected via a MUAV. The results of these surveys are analyzed to determine if there are statistically significant differences in the standard deviation and mean values of the condition ratings. Additionally, the operational performance of the MUAV was observed in various weather and field conditions. The results of this study will help transportation agencies to decide if MUAV technology can be adopted for inventory and condition surveys of roadside assets and maintenance activities.

The distress points, which are the numerical values assigned to pavement distress are not universal or standardized. Most agencies assign these points based on past experience with the intention to periodically calibrate them. The distress points significantly affect the distress indices, the life cycle cost, the remaining service life (RSL), and the accuracy of the pavement decisions. Distress data were obtained from four State Departments of Transportation. The data were analyzed and the RSL was calculated and equalized to the dollar values of the network and its rate of depreciation. Results of the analyses are presented in this paper. It is shown that the RSL could be calculated without the need to assign distress points. It is also shown that the weighted average RSL of the network reflects the dollar value of the network and its rate of depreciation. The RSL could be used to support accurate pavement decisions.

The remaining service life (RSL) of a given pavement section is the estimated number of years between now and the time when the pavement conditions reach certain amount of distress. The calculation of RSL is based on two steps; fitting the proper mathematical function to the time series condition data, and predicting the time at which the pavement reaches the threshold conditions. Time series pavement condition data of several miles of roads were obtained from four State Highway Agencies (SHAs). The data were analyzed and the RSL of each 0.1-mile section of each road was calculated based on the International Roughness Index, (IRI), rut depth and cracking data. Results of the analyses are presented in this paper. It is shown that, the RSL is a good communicating and strategy planning tool. It could be used to address engineers, the public, legislators and managers.

This article discusses the results of a research and development project to detect and evaluate inductive loops used in intersections for traffic detection and control using a step-frequency ground-penetrating-radar (SF-GPR) array. The frequency bandwidth, the dwell time, the transmitter-receiver patterns within the array, and the processing options defined the domain of an optimization effort to maximize the detection of the inductive loops. Descriptions of the application and the SF-GPR system and method are provided. A summary of the research effort and final results are presented. The inductive loops were detected and mapped at increasing levels of success with the optimization of data acquisition controls and data reduction options.

This paper describes a cost-effective traffic data collection system which is based on low bandwidth iDEN mobile network. An adaptive flow control protocol over the TCP/IP stack was developed to ensure a "best-effort" style data transmission over the low bandwidth network while the data link status is monitored to avoid unnecessary drop-offs caused by excessive demand of the wireless bandwidth. The iDEN handsets communicate via serial port with Caltrans field master signal controller using AB3418 standard. Signal phase and timing (SPAT) data from up to 10 signal controllers could be collected with one client at a maximum sampling rate of 200ms. Lab testing at California PATH showed that the data collection system based on the adaptive flow control provides an average upload data rate of 2.68kps per remote client for over 95% of the time, which could support SPAT sampling rate up to 200ms. Overall for more than 98% of the time the measured system availability is greater than 98%. The lab testing of the data collection showed significant improvement in the availability of the data collection system when compared with the transmission without our adaptive flow control protocol.

An application for traffic signal control using reinforcement learning agents was implemented for small traffic networks with volumes close to saturation. The state observed by the agents and the rewards included information from the intersection being controlled and also from adjacent intersections. Communication between neighboring agents resulted in emergent coordination between agents and ultimately in better handling of traffic. Lower average, maximum and minimum delay values were found for the two tested networks compared to optimal pre-timed settings. Trends indicate that if the minor intersecting streets are one way, increased organization and coordination of traffic are expected as the network size increases. There is potential for reinforcement learning agents in traffic control applications as they can provide control in real time with flexible timing settings. Further research is being conducted with variable volume, bigger networks, and adjusting the agents' parameters.

One common way to measure the levels of service of signalized intersections is to estimate delays. The call for better methods for estimating delays is the source of much research that culminated in the Incremental Queue Accumulation (IQA) method. The IQA method consists of two procedures: IQA field and IQA model. Both procedures require intensive cycle-by-cycle data collection on approaching vehicles and traffic signal timing. In a study to evaluate the accuracy of the IQA method, the real-time remote data collection facility available at the Transportation Laboratory of Brigham Young University was used to create a digital video that simultaneously records the four approaches to a signalized intersection, together with signal changes for the four approaches. By using a video image analysis program that allowed frame-by-frame analysis, it was possible to collect both vehicle arrival/departure and signal timing data that were necessary for evaluating the two IQA delay analysis procedures.

Although IntelliDrive has spurred significant research, little has been done to investigate the possibility of using traffic density information to time the release of in-vehicle guidance information. This study evaluated drivers' reactions to guidance information under varying traffic conditions to identify if such an integration of data is warranted. Researchers used a vehicle-driving simulator and participants between 18–25 years old, those with the highest US crash rate. The findings indicated that vehicle voice guidance software does not significantly distract drivers more than manually searching for road name signs. Results also suggest there is a direct relationship between the road segment level of service and the effectiveness of route guidance systems.

The focus of this paper is (1) to explore features available in commercial Geographic Information Systems (GIS) software and estimate accessibility index as a function of potential captive riders for each transit stop, and, (2) identify spatial gaps based on accessibility index to provide improved public transportation systems that maximizes market potential. Potential captive riders are identified within a pre-defined accessible walking distance or walking time (0.25 miles or 5 minutes) from each transit stop in the City of Charlotte, North Carolina. These riders comprise unemployed, household population with 0 or 1 automobiles, population by age group, low income population (< $25,000), and ethnicity. Results from statistical analysis conducted considering transit ridership and estimated accessibility index show that market potential can be maximized by selecting transit stop locations with high accessibility index or in locations with high accessibility index. Therefore, the methodology and estimated accessibility index to identify spatial gaps helps expand transit area coverage, identify new routes and transit stops.

Advanced Traveler Information Systems (ATIS) provide a vital platform to assist travelers in planning more informed trips on route selection and diversion for congestion avoidance and safety enhancement. As one major information dissemination mode, Dynamic Message Sign (DMS) can provide real-time en-route information including roadway congestion situations, construction activities, incident events, and diversion needs. Compared with traditional text-only messages, graphic-aided messages can be better recognized and understood. Although text-based DMSs have been in operation for many years, research on graphic-based DMSs is still in its early stages. To enhance our understanding of critical issues on designing suitable graphic-based DMSs, this study concentrates on design of an innovative Graphic Route Information Panel (GRIP), and proposes a methodology for understanding its potential usefulness to drivers. An online survey is employed to examine sign rates of understanding by and usefulness to drivers. In addition to basic statistical analysis of the survey results, a Logit model is employed to investigate the significance of various drivers' characteristics and design attributes impacting the effectiveness of GRIPs.

Pavement service life can be defined as the estimated number of years between pavement construction or rehabilitation and when the pavement section reaches a given condition (rutting, cracking, roughness, etc.) threshold value. At that time, the pavement section is typically subjected to rehabilitation or preservation actions. The two overarching methodologies for determination of pavement fix benefits are: 1) the extension in the pavement service life due to a given fix and 2) the calculation of the area between the pavement performance curves and a given threshold value. The life extension method places importance in prolonging the service life of the pavement. On the other hand, the area under the performance curve method places importance on the level of pavement distress over time. Selection of the pavement fix type and time with the lowest cost to benefit ratio could be considered "optimal".

This paper addresses the problem of moving wholesale and retail goods around the New York City Metropolitan Regional Area. The existing roadways, bridges, and tunnels have already exceeded their capacity, and the author has assumed that freight traffic will continue to grow at the same rate as the population. To address this problem, a freight railroad tunnel under the Hudson River should be constructed to interconnect the west side of the Hudson River to the entire New England Regional Area and also to Long Island. This proposed railroad freight tunnel connection could remove over 30,000 tractor trailers per day, or about 8 million trucks per year, from the congested roadway network and the Hudson River Crossings.

The Wright Brothers' invention changed the way we live and air travel has transformed our world. It is a fascinating story on how an injury in a hockey game changed Wilbur Wright's career plans. This paper relates the story and how his career evolved with his brother to build bicycles and then develop the airplane and an aircraft manufacturing company.

The conventional approach to preparing programming documents for new facilities is a process that tends to favor "stove-piping". Once a facility is planned and a program definition document has been prepared, often the project is turned over to design, and once designed, the project is turned over to construction. Little input is derived from the designers and constructors during the planning process, and during design, the input from the planners is thought to end. Likewise, when a project that enters construction, there is less input from the designers and the planners. The Metropolitan Washington Airports Authority (Airports Authority) has sought to invest all stakeholders in the success of a project by developing a collaborative planning, design and construction process that involves all three disciplines from the conceptualization of the project through its turnover to users. The intent of the process is to make sure that the completed project meets the goals and objectives first laid out in the planning phase, and to assure that all project costs are accounted for and that goals for schedules and budgets are identified early in the process and adhered to through completion. This collaborative effort has been used with success on some initial smaller projects at both Reagan National and Washington Dulles International Airports, and is now becoming the standard process for execution of larger projects.

Shortly after the City of Chicago announced its plans for the O'Hare Modernization Program (OMP) in 2001, the Federal Aviation Administration (FAA) established a project office to oversee the Agency's participation in the program and provide a focal point for the City of Chicago. As the planning and design of the program progress, the FAA's role in the OMP grows and become increasingly complex. This paper will highlight existing FAA processes that have been adapted to work within the City's aggressive schedule. It will also introduce new positions, functions and processes established in order to meet schedule constraints and ensure compliance with FAA criteria for airport development and operations. The redesign of the Chicago area airspace and its integration with O'Hare airfield changes will be addressed. Lastly, the paper will highlight the complexity of safely operating one of the world's busiest airports while reconstructing that airport at the same time.

At 14,511-feet long, Runway 13R-31L is the longest runway at John F. Kennedy International Airport (JFK), and the second-longest commercial runway in North America. The runway's last major rehabilitation was in 1993. In anticipation of the next major repaving contract, and the need for JFK to maximize the efficiency of its runway and taxiway system, a multi-year program was initiated. The first step of this program included the development of a conceptual plan for the runway and associated taxiways to minimize delays and have the runway system conform to FAA Design Group VI standards. Using the conceptual plan a Constructability Study was performed that investigated traditional hot-mix asphalt (HMA) rehabilitation as well the placement of a Portland cement concrete (PCC) overlay on top of the existing HMA surface, and included life-cycle costs, staging options and construction durations. A series of briefings were held with the airlines and the FAA to present the study's findings and to get their buy-in to the final plan. Development of the contract documents to widen the runway to 200 feet using (PCC) and to construct the new taxiways followed the completion of the Constructability Study. A series of peer review meetings as well as a contractor's workshop were held during the development of the contract documents to ensure that all elements of the construction were addressed. In June of 2009, this contract was awarded. Construction of a test section was completed in November 2009, and a series of lessons learned meetings followed. On March 1, 2010, the runway was closed to operations for reconstruction. Construction is scheduled to be completed in November 2010, with a significant portion of the runway returned to service during the summer of 2010. This paper presents a case study covering the planning, design and construction of this significant project.

The need to preserve our airfield pavement infrastructure is paramount to insuring the viability of transportation of people and goods. Preventive maintenance plays an important role in the preservation of airfield pavement infrastructure. A successful preventive maintenance program cannot function without the support of many features associated with pavement management systems (e.g., pavement inventory, condition assessment, and the framework for the identification and prioritization of pavement preservation treatments). The purpose of a preventive maintenance treatment is to prevent premature deterioration of the pavement, retard the progression of pavement defects, and cost-effectively extend the life of the pavement. The objective is to slow down the rate of pavement deterioration and effectively increase the useful life of the pavement. A preventive maintenance treatment is not determined by the type of treatment, but by the reason why the treatment is performed. For cost-effective preventive maintenance it is necessary to apply the right treatment to the right pavement at the right time. The objective is to identify the sections that would benefit most from preventive maintenance (the right pavement), do the identification and apply the treatment in a timely manner (the right time) and to select the most beneficial treatment (the right treatment). The effectiveness of preventive maintenance is largely dependent on the timing of maintenance activities. To ensure that funding for preventive maintenance is available when required, many practitioners advocate the establishment of adequate dedicated funds for preventive maintenance. The development and implementation of a preventive maintenance program should be done in a collaborative manner, and should be supported by training and educational activities. To succeed, a preventive maintenance program requires a long-term commitment, ongoing improvements, and the documentation and reporting of program benefits. This paper outlines 7 basic steps involved in developing and implementing a pavement preservation program for airport pavements and provides examples of decision matrices and life-cycle cost analysis procedures to apply and evaluate the success of pavement preservation treatments.

Geospatial airfield pavement evaluation and management systems (GAPEMS) have been implemented at Denver and Tampa International Airports that use the power of GIS for data collection, data integration, 100% pavement inspection, and geospatial analysis of remaining life. Surface condition data collected as part of GAPEMS was used to determine traditional network level Pavement Condition Index (PCI) data. PCI data alone, however, was insufficient in terms of understanding the performance of the pavements. A remaining life analysis was developed to integrate additional data into the process to determine project level maintenance and rehabilitation recommendations. A geospatial pavement evaluation and management system has the advantages of quick inspection time, full pavement coverage, project level data for maintenance and rehabilitation, and the ability to integrate other pavement data into the geospatial remaining life analysis. The benefits documented at both Tampa and Denver International Airports included an understanding of the failure mechanisms of the pavements, analysis of remaining life, and costs savings by shifting priorities to only those pavements in need of repair or replacement rather than pavements that reach a specific condition trigger level. Denver performed a GAPEMS inspection of the entire airport in 2006 and 2009 and the integrated geospatial remaining life analysis and geospatial data have been invaluable in shifting priorities for reconstruction. Tampa Airport completed an airport inspection in two parts in 2008 and 2009 and the geospatial pavement management system has allowed for the combining of maintenance and operational activities into an integrated airport GIS system. This allows the Operations Department to geospatially identify areas of concern for the Maintenance Department to address and update.

As our population ages, older air passengers face many challenges as they travel. Today there are over 40 million Americans over 65 years and projections are that this number will more than double by 2050 to almost 90 million. This paper defines what is old, examines the characteristics and demographics of older air passengers, describes what it is like to be old, explores the challenges that older passengers face in today's airports, and then discusses the approaches and opportunities as we plan and design future airports.

In order to increase arrival rates at many of today's heavily congested airports, simultaneous approaches, whenever possible, are conducted on parallel runways. For many years, the FAA has permitted simultaneous independent instrument approach operations only on parallel runways with a minimum separation of 4300 ft. Nowadays, new procedures have been developed to increase the utilization on closely-spaced runways, PRM/SOIA (Precision Runway Monitor/Simultaneous Offset Instrument Approach), one of the most recent of such procedures, allows simultaneous approaches in systems of runways spaced as close as 750 ft. Fraga et al. (2010) [6] using computer simulation showed the potential application of PRM/SOIA at Sao Paulo/Guarulhos International Airport (GRU) evaluating its impact on the airport runway hourly capacity. The present paper considering GRU as part of the airport system of TMA-SP (São Paulo Terminal Airspace) focuses on the influence of PRM/SOIA implementation at GRU on the system of main airports in the terminal airspace. Evidences were found that TMA-SP current overlapping approach procedures generate interferences on the operations of the airports in the system reducing the overall runway hourly capacity of the airports. In order to quantify this interference simulation was used to evaluate and to compare the airport system runway hourly capacity as opposed to the individual airport runway hourly capacity added up. It was found that TMA-SP airport system runway hourly capacity is about 30% less than the estimated overall runway hourly capacity of the airports alone.

The orientation of Airport runway requires information on wind speed, wind direction, and wind speed intensity and duration. On the other hand, the runway location design requires information on the latitude and longitude of the site, temperature variation at the site throughout 20 years period, and the altitude of the airport site, so that the x and y coordinates could be corrected. The design of runway requires information on the expected traffic volume, type of aircraft intending to use it, and the class of the airport as per the ICAO specifications. In this work, a computer program has been developed, with data base constructed inside, such data regarding the wind and temperature and the traffic data as explained above was fed to the data base. The latitude, longitude, and altitude of each of the eighteen provinces in Iraq were also fed to the system. A methodology for drawing the wind rose diagram and the conditions for selecting the best runway orientation through optimization process has been included in the data base. The required calculation procedures for basic runway length and the corrections usually adopted for variation of temperature and altitude, landing and takeoff situations were also fed to the data base in the system. An input sheet was designed through visual basic environment so that if an airport is required anywhere in Iraq, the system will ask for the basic data of latitude and longitude and will suggest the best orientation of the runway using the optimization technique. After suggesting the orientation, another input sheet will ask about the airport class required, the type of air craft, and the traffic volume and modes of takeoff and landing, and then the system will suggest the basic runway length required, and the required corrections to be considered for the environmental conditions. In order to check the validation of the software, Data of selected existing airports in Iraq were obtained and fed to the software so that a comparison of its output with the existing condition could be obtained. It was felt that such program will help in the management of airport design, and provide instant information regarding the runway orientation, location, and design.

There have been many improvements and innovations in the specialized technology involved with the emergency stopping of commercial aircraft when they have had an unplanned excursion from the landing or take-off runway. While these overruns and undershoots do not occur at a high frequency, when they occur the results can be disastrous. For more than fifteen years, ESCO-Zodiac Aerospace has been a pioneer in the commercial aircraft stopping business. ESCO's Engineered Material Arresting Systems (EMAS) has led the way with a system that has gone beyond Federal Aviation Administration (FAA) acceptance in 1996 to become a proven life saver. In the more than half dozen times that an aircraft emergency has resulted in an aircraft in an EMAS bed, the system has worked successfully. More than 200 people have been protected from serious injury or death because of the presence of an EMAS in the Runway Safety Area (RSA) at the end of a runway. All aircraft that have entered an EMAS have subsequently flown from the airport in less than two weeks and continued on in revenue service. Because of a continuous improvement perspective on the part of the designer and manufacturer, there has been a continuing stream of innovations for the EMAS process. The purpose of this paper is to provide an overview of the current state of the practice of EMAS design by highlighting the numerous recent innovations in the product, design and construction of EMAS systems. With as much detail as can be provided for a proprietary product, the innovations of the basic EMAS block will first be reviewed. Second, the EMAS design process improvements will be summarized. Finally, the alternatives for construction of an EMAS bed will be revealed. The paper will summarize these past innovations and also offer a quick look into the future of this well-developed safety system, touching on some of the possible future innovations.

Using a medium-sized Towbarless Towing Vehicle (TLTV) (16.8 tonnes (37,000 lb)) as an example, a comparative analysis is given of braking performance when applying either the TLTV brakes alone or the aircraft brakes alone when bringing a TLTV/aircraft combination to a complete stop from high speed and at maximum braking. It is shown that the stopping distance with tractor braking alone can be up to five times longer than the stopping distance with aircraft braking alone. It is also shown that the nose gear forces generated with aircraft braking alone can be excessive for lighter aircraft but allow a reasonable safety factor for heavier aircraft. Therefore, depending on the tractor/aircraft combination, it is possible to allow an operator in the cockpit of an aircraft being towed to apply the aircraft's brakes during an emergency. Each specific combination of tractor and aircraft should be analyzed separately before making such a determination for that combination.

National and international regulations define requirements for bearing capacity of runway strip and runway end safety areas. Bearing capacity requirements imply the reduction of damages to an overrunning aircraft, facilitating its deceleration and allowing the easy access of emergency vehicles. In particular, international regulations from ICAO impose a maximum sinking of the aircraft nose landing gear into the soil. Hence, any functional and structural intervention in such areas should take into account this goal. Furthermore, interventions in airports infrastructures should imply minimum interference to airport activities and should comply with sustainability and environmental requirements. In this context, an innovative methodology, called "Controlled Compaction Energy Approach" was developed to stabilize soils in situ. The innovative approach does not have as main goal the maximization of density and bearing capacity as is usually the goal in traditional in situ stabilization procedures; the achievement of regulation requirements is based on the control of the compaction energy applied after stabilization, in order to develop only the required bearing capacity to obtain a surface that is not too stiff to be able to dissipate enough aircraft energy. The compaction energy needed strongly depends on different variables, such as the interstitial voids and water content and the amount of binder. A full scale test area was developed in order to set up the technique; afterwards, a real scale application of the method was carried out at Linate Airport of Milan (Italy) within the functional requalification of the runway end safety area (RESA). Such RESA is currently under operation for about two years.

Stewart International Airport (SWF) is located west of Newburgh, New York, in the southern Hudson Valley, and 60 miles (88.5 km) north of New York City. It was originally developed in the 1930s as a military base to provide aviation training for the cadets at the nearby United States Military Academy at West Point. Over the years, it has grown into the major passenger airport for the mid-Hudson region and continues to serve as a military airfield. Currently, SWF houses the 105th Airlift Wing of the New York Air National Guard. In 1991, the commercial service airport went private when United Kingdom-based National Express Group was awarded a 99-year lease on the airport by its owner and operator at that time, the New York State Department of Transportation. On January 25, 2007, the Port Authority of New York and New Jersey (PANYNJ) Board of Commissioners voted to acquire the remaining years of the airport's lease, effectively ending the privatization of SWF. The PANYNJ assumed control of the airport on November 1st ofthat year. Prior to taking over the airport, the PANYNJ projected that the airport's annual passenger traffic would soon be triple that of 2006. In 2007, Stewart International Airport achieved this and handled 970,000 passengers. At that time, it became apparent that the airport lacked adequate parking facilities to address the rapid increase of annual passengers and the holiday seasonal demands. Although air travel at SWF decreased following the recent economic downturn, demand for parking is expected to increase, backed by a 2010 customer survey at SWF that showed 65 percent of the airport's passengers arrive by personal car, and 28 percent use the airport's parking facilities. In addition, forecast passenger growth for the next decade projects passenger levels to ultimately exceed 2007 totals. This led the PANYNJ to embark on the expansion of the Terminal's Lot "A" public parking facility, increasing it from the current 8.7 acres to 15.1 acres. The PANYNJ Engineering Department issued Contract No. SWF 164.007 for expanding the parking lot facility. The expansion consists of a pervious asphaltic pavement and an extensive surface and subsurface storm drainage collection system. It is designed to collect, detain and allow infiltration of the 100-year storm run-off without any peak discharge into nearby streams and open water bodies, and also recharge the groundwater table. Best management design practices include the use of infiltration bio swales, a granular pavement sub-base with large void content, installation of "raintanks" and a sub-drainage piping system. In addition, a portion of the storm water run-off will be diverted into a cistern and utilized by an underground irrigation system with solar powered pumps for the watering of the parking lot's landscaped areas.

The traditional approach of reducing green house gas and air pollutant emissions is to reduce fuel consumption. However, the criteria for getting a taxiway or runway approved for FAA funding does not involve consideration of air emissions but only a reduction in delay. When the cost of reduced delay exceeds the cost of construction the project can meet a minimum threshold of benefit/cost ratio of 1.0 and, therefore, can be considered for FAA funding. The paper examines the case of the 2006 Houston George Bush Intercontinental Airport (IAH) master plan which recommended capacity enhancements to reduce delays by constructing two runways and end around taxiways. However, the end around taxiway alone has been shown to substantially reduce delays and reduce fuel consumption. The FAA's Emission and Dispersion Modeling System (EDMS) was applied to characterize pollutant emissions with and without the improvements and the reduction of annual fuel consumption was used to estimate green house gases (GHG) reductions. The paper concludes that the reductions in pollutant emissions and GHG were significant and should be quantified to add to the benefit for prioritizing airport improvement projects competing for funding. The paper also suggests that in this particular case the reduction in criteria pollutants alone could be justification to begin construction of the end-around taxiway.

The Dallas/Fort Worth Metropolitan Statistical Area (MSA) is the nation's fourth largest urban area, with an estimated population of about 6.5 million people. This area is served by two commercial airports: DFW International (DFW) and Dallas Love Field (DAL). Those airports also serve the residents of the counties surrounding the limits of that MSA; in fact, to the North (where the population growth is concentrated), no commercial airports are available until Oklahoma City, Will Rogers World Airport (OKC). The North Texas Regional Airport (GYI) is located midway; this airport is currently undergoing major improvements, and with the increase in demand in the near future it could play an important role in the air transportation system of the region. This paper outlines the possibility that GYI can meet a portion of the air travel demand from the northern boundaries of the expanding DFW MSA, and from "Red River" counties along the Texas-Oklahoma border. For population living in this region, an expanded GYI would be the ideal airport among those in the DFW area or OKC. The authors define the GYI Primary Airport Service Region (ASR) as the territory within a 90-minutes drive time from the airport. The trip rate (TR) the number of round trip flights per region resident in the ASR is then estimated using the DFW MSA trip rate with a reduced number to reflect the economic activity in the GYI ASR; this leads to a forecast of the potential GYI passenger activity for the next twenty years. The recommended course of action to move from a general aviation to commercial aviation is indicated into three distinct phases, short, medium and long term. Phase 1, introducing cargo activities, Phase 2, begin non scheduled operations, and Phase 3, scheduled operations. The method applied to GYI study could be used to analyze similar general aviation airports that exist in other metropolitan regions.

Airside infrastructure, Terminal along with Ground access facilities, form three broad components of any airport. An airport attracts large number of passengers, meeters and greeters and staff depending upon its size, location and role. Efficient ground access system is therefore vital for any airport to serve its full potential. Indira Gandhi International Airport (IGIA) in New Delhi is a crucial airport, which is being upgraded and modernized by Delhi International Airport Limited (DIAL) under Public Private Partnership (PPP) initiative, covering funding, designing, construction, operations and maintenance of the airport for a period of 30 years till 2036, with a further option to extend it by next 30 years. The first phase is marked by construction of new integrated terminal T3 by 2010 to handle 34 million passengers per annum. This would be followed by three more passenger terminals till 2026 in subsequent phases. This paper presents an overview of the concept of the central spine and the connecting network within the airport boundary, design concept, other general details such as Ground access facilities, both by roadway and by metro express link, curbside configuration, multi level car parking along with parking for buses and taxi staging, express bus service to various city centers, shuttle bus service linking different parts of airport, integration of circulation plan of cargo complex and hospitality districts.

The geographical distribution of air passenger trip origins forms a critical input to studies of airport ground access and airport choice. This paper discusses the limitations of typical air passenger surveys to determine the distribution of air passenger trip origins at a required level of resolution, the resulting need for air passenger trip generation models, and considerations that arise in developing such models. The paper then presents a set of air passenger trip generation models that were developed to support the current update of the Bay Area Regional Airport System Plan Analysis and discusses their strengths and limitations. The paper concludes by discussing the need for additional analysis to improve the future utility of the models and the potential transferability of these models to other regions.

Ground access mode choice models play a key role in airport ground transportation and airport system planning studies. The paper presents the findings of a recent Airport Cooperative Research Program Synthesis study that reviewed the current state of practice of airport ground access mode choice models, and discusses the range of model specifications adopted in recent studies. The paper examines the associated data issues that arise with different model specifications and discusses the implications for air passenger and other airport user surveys undertaken to support the development of such models. The paper concludes with a set of best practice recommendations for future development of airport ground access mode choice models.

For the characterization of the permanent deformation behavior (rutting) of asphalt concrete (AC), the triaxial cyclic compression test (TCCT) is a standardized test method. The test simulates traffic loading by applying a sinusoidal compressive stress in vertical direction and a radial confining pressure, which simulates the confinement of the specimen within the pavement structure. As a result the permanent axial strain versus load cycles is obtained. In the standard test procedure the confining pressure is held constant throughout the test to simplify the test control. However, in reality the confining pressure oscillates in a sinusoidal way with a certain phase lag to the vertical loading due to the viscoelastic characteristics of AC. The phase lag of hot mix asphalt (HMA) depends on the temperature and load frequency. The paper presents an innovative approach to improve the TCCT by implementing sinusoidal confining pressure. Strain gauges are attached directly to the specimen's surface to measure the radial deformation and to obtain the phase lag between the axial loading and the radial reaction. These experiments are carried out for various mixtures at temperatures ranging from 10°C to 50°C and frequencies from 0.1 Hz to 30 Hz. Thus, radial strain and phase lag can be analyzed as a function of temperature and loading frequency. In a second step the sinusoidal confining pressure with the obtained phase lag will be implemented into the test routine and results from standard TCCTs with constant confining pressure versus improved TCCTs with oscillating pressure can be compared and discussed.

This study was conducted to evaluate the effect of recycled asphalt pavement (RAP) amounts on the rutting resistance of plant-produced SUPERPAVE asphalt concrete (AC) mixtures in the laboratory. RAP amounts ranged from 0 to 25 percent by weight of mixture. Tests conducted included the dynamic modulus test at multiple temperatures and the flow number (FN) test at 54°C to characterize the stiffness and rutting resistance of the mixtures, respectively. Significant differences in rutting resistance were observed even though the mixtures considered were designed for similar levels of traffic (between 3 million and 10 million design equivalent single-axle loads). The effect of RAP amount on rutting resistance was unexpected as FN decreased as the RAP amount increased from 10 percent to 25 percent. The practice of allowing softer binders for AC mixtures containing high RAP amounts (>20%) was suggested as a possible reason for the relatively lower rutting resistance at the 25 percent RAP level. It was concluded that the use of a high RAP amount in combination with the softer binder may have the inadvertent effect of reducing the rutting resistance of certain AC mixtures. Future work involving a larger set of AC mixtures than presented in this paper is recommended.

In recent years, more and more highway agencies are adopting preventive maintenance strategies or thin surface treatments to bring pavements back to appropriate serviceability for road users. This paper discusses the effectiveness of several thin surface or preventive maintenance treatments on sixteen highway test sections in Kansas. The treatments studied include thin Hot-Mix Asphalt (HMA) overlay, ultra-thin bonded asphalt surface (Nova Chip), and chip seal. These treatments were applied with three different types of surface preparation- bare surface, 1" surface recycle (hot in-place recycling), and 2" surface recycle. Hamburg Wheel-Tracking Device (HWTD) test was conducted on the cores from the test sections with thin surface treatments under this study. The laboratory test results show that most projects exceeded the maximum rut depth limit (20 mm) specified in the study and the number of wheel passes to failure varied significantly among the projects. Cores from only three projects, two treated with Nova Chip and one with 1" HMA overlay, carried 20,000 wheel passes without exceeding maximum rut depth limit. Pair-wise comparisons or contrasts among the treatments were performed with the statistical analysis software, SAS. Air void of the HWTD test cores was found to be a significant factor affecting the performance of thin surface treatments. Since the Hamburg test samples (62 mm tall) consisted mostly of underlying layer materials, it was concluded that quality of this layer is the major determinant of performance of pavements with thin surface treatments.

Transportation infrastructure facilities such as highways consume large quantities of materials in initial construction and periodic maintenance and rehabilitation. A Superpave asphalt mixture with 4.75-mm nominal maximum aggregate size (NMAS) is a promising, low-cost pavement preservation treatment that can be applied in thin lifts for low- to medium-volume facilities. This study evaluates the performance of 4.75-mm NMAS Superpave asphalt mixture and proposes an optimized mixture design for a long-lasting ultra thin hot-mix asphalt (HMA) overlay. Twelve different 4.75-mm NMAS mix designs were developed in the laboratory using two binder grades and three different percentages of natural (river) sand in combination with finer quarry materials. Test results from two laboratory performance tests show that rutting and moisture damage of such mixes during Hamburg Wheel Tracking Device and Lottman tests are aggregate-type and source specific. Anti-stripping agent affects moisture sensitivity test results irrespective of natural sand content and binder grade. Finally, optimum combinations of aggregates and binder were developed for 4.75-mm NMAS mixture based on the statistical analysis of performance data.

In this work, pavement cross-section as stipulated by the Indian Roads Congress code of practice for pavement design was used in the stress-analysis. Typically, two types of asphalt layers are laid over three to four layers of granular materials for pavements constructed for heavy traffic volume in India. Asphalt mixtures pertaining to these top two layers were fabricated with polymer modified and unmodified asphalts in the laboratory. These mixes were tested in the simple performance test equipment at temperature of 60 °C under a wide range of frequencies. A four parameter Burgers' model was used for fitting the experimental data for both the asphalt layers. A two-dimensional finite element model of the pavement structure was used within the ABAQUS computing environment. The granular base, subbase and subgrade granular layers were assumed to be elastic. The pavement model was subjected to cycles of periodic loading and the stresses and strains were monitored at all the critical locations. This was used to quantify the influence of modifiers on the mechanical response of the pavement and parametric analysis was carried out to find out enhanced service life of the asphalt layers that could be achieved due to the use of high-performance materials.

With premature deteriorations and performance limitations of hot-mix asphalt (HMA) pavements, innovative solutions are needed to enhance fatigue life or rut-resistance of HMA. Various reinforcing methods are widely utilized such as installing geogrid, geocomposite, or geomembrane layers at the bottom HMA to improve the structural integrity of HMA pavement. Such layered systems sometime improve the field performance of HMA; however, such solutions may not enhance toughness, tensile strength, or shear strength of HMA itself due to the location of interlayer systems. A new mono-strand fiber reinforcing material for HMA is proposed in this study to effectively reinforce the HMA not only at the bottom but also inner-side. Adding a small amount of fiber into HMA leads to significant increases in the phenomenological fatigue life of fiber-reinforced HMA compared to the conventional HMA, and four-point bending beam and indirect tensile tests are performed to observe the effect of fiber reinforcement.

Construction of the new Guo Shien Bridge (GSB) included a steel orthotropic bridge deck. The higher flexibility of an orthotropic deck could cause a pavement placed upon it to fatigue and crack more quickly than a pavement placed on a normal roadway. The Guss asphalt mixture was applied to the steel deck pavement for the GSB. When heated to high temperatures, the Guss mixture is designed to be pourable asphalt mastic to provide an impermeable and durable layer for the steel deck surfacing. The basis of this paper was to evaluate the mixing and placing characteristics of the Guss asphalt mixtures. Various tests including Lueer fluidity, indentation, bending flexibility and wheel tracking were conducted to analyze the engineering properties of the Guss asphalt mixture for durability. Practical guidelines were given to enhance the quality of Guss asphalt mixtures. This paper was to provide background information on orthotropic bridge deck construction practices and document the construction of the Guss asphalt mixtures on the GSB.

Moisture damage in flexible pavements might cause stripping in the asphalt pavement and ultimately lead to premature failure. In addition, rising energy prices, global warming, and more stringent environmental regulations have resulted in an interest in warm mix asphalt (WMA) technologies as a mean to decrease the energy consumption and emissions associated with conventional hot mix asphalt production. In this study, the objective was to conduct a laboratory investigation of long-term influence of anti-stripping additives on moisture damage in WMA mixtures. The test results indicated that the aggregate source did not show a remarkable effect on moisture susceptibility of mixture in this study. The addition of anti-stripping additives increased the ITS, TSR, and flow values; however, the differences were not statistically significant compared to the control mixtures. Mixtures containing Asphamin® did not perform as well as others. In addition, an increase of condition duration decreases the anti-stripping resistance regardless of mixture type.

The Superpave asphalt binder specifications are intended to improve pavement performance by limiting the potentials for plastic deformation and cracking. Hot-mix asphalt (HMA) behavior depends on the binder's—temperature susceptibility, and the rate of loading. The binder viscosity temperature susceptibility (VTS) characterization plays a major role in determining the HMA dynamic modulus (E*) master curve, especially when input Level 3 is used in the M-E PDG. For input Levels 2 and 3, E* could be predicted by the Witczak equation, whereas, three test methods are specified to determine the asphalt binder VTS. These tests are (i) dynamic shear rheometer (DSR) for determining shear modulus (E_b*) and phase angle (δ); (ii) conventional tests such as penetration, kinematic and absolute viscosities, and ring and ball softening point; and (iii) rotational viscosity. All test methods can be utilized to determine the ASTM "A-VTS" parameters. In this paper, the A-VTS parameters for twenty two (22) neat and polymer modified binders were obtained from the three test methods and compared. The results show that A-VTS parameters from the three tests could be significantly different. Further, the impact of the VTS parameters' variations on the E* master curve and on the predicted flexible pavement performance are discussed.

The temperature-viscosity relationships for twenty two neat and modified asphalt binders were evaluated using conventional tests (CT) such as penetration, kinematic and absolute viscosities, and ring and ball softening point; rotational viscometer (RV); and dynamic shear rheometer (DSR). The temperature ranged from 25 to 135 °C, 100 to 185 °C, and 7 to 82 °C for conventional, RV, and DSR tests, respectively. Results from several binders studies have revealed that binders having similar penetration, viscosity and performance grade (PG) could show dissimilar rheological behaviors. Hence, there is a need to fully characterize asphalt binders to capture their rheology over a wide range of temperatures and loading frequencies. The activation energy (AE) concept was utilized in this study to characterize the temperature susceptibility of the asphalt binders. Correlations between AE and binder rheological properties (e.g., G*/sinδ and G* sinδ) were evaluated. In addition, a relationship between AE and useful temperature range (UTR) determined from the performance grades (PG) was developed. The advantages of characterizing the relative temperature susceptibility of the binders using AE are discussed. Finally, discussion on mixing and compaction temperatures, especially for polymer modified binders, by using AE is also included in this paper.

One important factor related to the asphalt pavement performance is the transitory nature of asphalt. Heating asphalt from – 40 to 150 °C, one can observe the transition from glassy solid to viscoelastic solid, viscoelastic solid to viscoelastic fluid and finally to Newtonian fluid. This study focuses on capturing the viscoelastic solid-fluid transition. Specifically, this transition was captured here by the storage modulus (G') and loss modulus (G") cross-over when the sample is subjected to a temperature sweep with constant strain amplitude and frequency. Since this measure depends on frequency of testing, this study also quantifies the influence of frequency. Two types of asphalt of the same grade but manufactured by different process (blending and air blowing) were tested at unaged, short-term aged and long-term aged conditions. The G'-G" cross-over point changes at low frequency and the frequency dependency vanishes above 40 Hz. This frequency independent G'-G" cross-over temperature can then be truly called as the viscoelastic transition temperature or sol-gel transition temperature. It was interesting to note that the aging conditions did not alter the frequency dependency. Also there was no significant difference in cross-over temperature of blended and air blown asphalt.

Superpave^TM performance-graded asphalt binder technology continues to advance with some producers focusing on the use of additives to enhance the performance of asphalt binders. A common practice is to modify an asphalt binder with a polymer to extend the high- and low-temperature range. However, agencies require a method to verify the presence of the polymer. The method that is presented serves to demonstrate that gel-permeation chromatographic (GPC) can be used to detect the presence of polymers in asphalt binders. Typically, the polymers used in asphalt binders have a number average molecular weight ranging from 300 to 600 times larger than the number average molecular weight of asphalt binders. The GPC technique separates the polymer from the asphalt binder as a function of molecular size. The analysis of eight unknown samples, some of which were reported to contain a polymer, was conducted. The GPC results demonstrated that three of the asphalt binders were polymer modified while the remaining five asphalt binders were not modified. After the results were reported, the actual composition of the asphalt binders was revealed and found to be in agreement. Thus, GPC can be used as a simple screening test to identify when asphalt binder has been modified with a polymer.

Despite the positive effects, the use of wax-based warm mix additive is very limited due to the concerns on cohesion and adhesion properties. The objective of this study is to evaluate the cohesive strengths of asphalt binders with and without Sasobit®, a wax-based warm mix additive using a pneumatic adhesion tensile testing instrument (PATTI) and using surface free energy method from optical advancing contact angle measurements. Two asphalt binders, PG 64-22 and PG 76-22M with and without 2% Sasobit® were coated in 2"X2"X1/4" glass plates. Cohesive strengths of asphalt binders were obtained in terms of pull-off tensile strength (POTS) using ½ in diameter pull-stubs. It was observed that the cohesive strengths of PG64-22 and PG76-22M are 1.964 MPa (284.9±21.3 psi) and 2.067 MPa (299.9±15.3 psi), respectively. Sasobit® reduced the cohesive strengths to 1.468 MPa (212.9±11.3 psi) and 1.503 MPa (218.0±17.7 psi), respectively for PG 64-22 and PG 76-22M. The cohesive strengths (free energy of cohesion) obtained from surface free energy measurements indicate that PG 64-22 has higher cohesive strengths and Sasobit® increases the cohesive strengths of both the binders. Overall, pull-off test was found to be simple and reproducible.

The new Mechanistic-Empirical Pavement Design Guide (MEPDG) provides methodologies for mechanistic-empirical pavement design as opposed to the empirical methodology used in the 1993 American Association of State Highway and Transportation Officials (AASHTO) pavement design guide. The objective of this study was to compare the pavement designs obtained using the 1993 AASHTO and the new MEPDG methods for typical Portland Cement Concrete (PCC) and Asphalt Concrete (AC) pavements in Kansas. Five in-service Jointed Plain Concrete Pavement (JPCP) projects were reanalyzed as equivalent JPCP and AC projects using both approaches at the same reliability level. The results show that the new MEPDG analysis yielded thinner AC sections for all projects than those obtained from the 1993 AASHTO design guide analysis. Four of the PCC sections, designed using the 1993 AASHTO design guide, were thicker than the sections obtained with MEPDG. The MEPDG analysis resulted in thicker PCC slab for the fifth project. Effect of change in performance criteria on the thickness of AC and PCC sections has also been investigated. It has been found that AC sections are more sensitive to change in performance criteria as compared to PCC sections using MEPDG versions 1.0 and 1.1. In general, difference in thickness using both versions is not significant for all practical purposes.

Axle load spectra have a significant impact on predicted pavement performance. At the design stage, it is typically assumed that axle load spectra as measured by weigh-in-motion (WIM) systems are accurate. In fact, the quality of WIM-based data has inherent uncertainties due to inaccuracy and systematic bias in measurements. This paper investigates the impact of WIM measurement errors on axle load spectra (ALS) and quantifies the effects of these errors on design reliability. In the new Mechanistic-Empirical Pavement Design Guide (M-E PDG), the reliability procedure was developed based on the assumption that variability in performance prediction is approximately the same as the observed performance of the pavement sections used to calibrate the performance models. In this analysis, each distress type was approximated by a normal distribution and therefore, two parameters (mean and standard deviation) were determined to represent the expected value and associated variability by employing Monte Carlo simulation. The results show that the M-E PDG reliability analysis can compensate for negative axle load measurement bias for most of the distresses. However, a lower tolerance for negative bias needs to be enforced in order to ensure that both flexible and rigid pavements have the design reliability against cracking, especially for thinner pavements. While most of the findings further reinforce existing concepts, the study provides a systematic overview of WIM data accuracy and calibration needs and the impact of associated uncertainties on the pavement design process.

The Mechanistic Empirical Pavement Design Guide (M-E PDG) provides a number of new approaches for characterizing materials to be used in 21st Century pavement design. The M-E PDG software uses numerical models to analyze traffic, climate, subgrade and laboratory measurements of material properties to predict the performance of various pavement designs over their entire service life. A key element of the mechanistic design approach is the prediction of the response of the pavement materials, and thus of the pavement itself. The M-E PDG provides three hierarchical input levels: Level 1 is site/project specific with actual tests resulting in higher accuracy, Level 2 from less than optimal testing or by correlations and Level 3 from the agency database or user selected default values. Since obtaining Level 1 material inputs require considerable testing effort and cost, Level 1 data for M-E PDG analysis may not be possible all the times. In such situations, Level 2 or 3 inputs can still be used to perform M-E PDG analysis and predict design life of pavement. The objective of this study is to compare M-E PDG predicted distresses of different input level data from a recently constructed Continuously Reinforced Concrete Pavement (CRCP) project at I-64 Battlefield blvd, Chesapeake, Virginia. The original design of this pavement was done using the 93 AAHSTO design method several years before the construction. This paper also documents the efforts associated with the laboratory and field procedures used for level 1 input characterization. The FHWA Mobile Concrete Laboratory (MCL) had performed all the concrete materials characterization for level 1 input on this project. M-E PDG software (version 1.1) is used to obtain the predicted distresses for the pavement structure using the same thickness obtained by AASHTO method. This paper also discusses the difference in predicted distresses when level 1 and level 3 traffic data was used. Results shows that there were significant differences in predicted distresses between Level 1 and Level 3 concrete properties inputs for M-E PDG analysis depending upon the type of Level 3 input used.

HMA dynamic modulus (E*) is one of key inputs to the Mechanistic-Empirical Pavement Design Guide (MEPDG). There are two different E* models in the MEPDG; the NCHRP 1-37A viscosity-based model, and the NCHRP 1-40D, which is based on the binder shear modulus. This paper focuses on evaluating the influence of the binder characterization input level on the predicted E* in MEPDG. Laboratory E* tests were conducted on samples from 15 different HMA plant-produced mixtures. The shear modulus (G*) and phase angle (δ) for each binder were also determined in the laboratory. Results showed that MEPDG levels 1and 3 binder characterization inputs with both E* predictive models yielded E* values that are in excellent to fair agreement with laboratory measured E* . However, the 1-37A model showed better results than the 1-40D model. On the other hand, high bias in E* values was observed when level 1 binder characterization data was used.

Several in service pavements located in different regions of Idaho that have been designed according to the ITD design method were redesigned using the AASHTO 1993 as well as the Mechanistic-Empirical Pavement Design Guide (MEPDG) procedures. All designs were conducted at a 50% reliability level. The nationally calibrated MEPDG (version 1.1) was used to predict the performance of the three design methods. Level 2 subgrade material characterization inputs were used in the MEPDG analysis. All other MEPDG inputs were level 3. Performance indicators predicted using MEPDG related to the three design methods were compared to each other. Results showed that, relative to AASHTO 1993 and MEPDG procedures, ITD design method significantly overestimates the thickness of the pavement structure, and particularly the thickness(s) of the unbound layer(s). On the other hand, the AASHTO 1993 and MEPDG guides show reasonable agreement on the resulting pavement structure.

Although widely applicable and useful, the traditional CBR test does not provide the mechanical behaviors such as resilient and permanent deformation characteristics of granular road materials. A relatively simple testing technique is developed to characterize the resilient modulus of granular materials based on the traditional CBR test using repeated load cycles. The Finite Element Method (FEM) analysis has been attempted for the purpose of modeling the Repeated Load CBR and derives an equivalent resilient modulus of the sample as a bulk. Strain gauges were used to measure the lateral deformation of the CBR mould from which the confining stress can be estimated to determine a stress dependent resilient modulus. Furthermore, a large scale cyclic load triaxial test was carried out to validate the result of the repeated load CBR on coarse granular materials from South Africa and Ethiopia. The repeated load CBR test is quite useful to estimate the resilient modulus of unbound granular materials that can be used as an input in mechanistic pavement design analysis in the absence of triaxial testing facilities.

The National Center for Asphalt Technology (NCAT) Test Track has generated valuable information related to the installation of gauges, methodology for data collection and data analysis. However, information regarding the effect of pavement instrumentation on in situ properties is nonexistent. The objective of this study was to evaluate the effect of pavement strain gauges on the in situ density. In 2009, during construction of two test sections it was necessary to remove and replace the bottom lift since quality control targets were not met. Prior to removal, cores were taken in the gauge array and outside the array so that a two-sample T-test could be conducted for each section, respectively. The results showed that there were no significant differences between air void content and consequently no negative effect caused by the presence of pavement instrumentation. Additional density testing was conducted in and around the gauge array in these two test sections after completion of the surface layer. The data indicated no difference in measured density resulting from the presence of embedded instrumentation.

To produce a high-quality and long-lasting pavement, quality assurance (QA) is critical. For flexible pavements, layer thickness and in-situ density are the two most important characteristics to monitor. This paper presents the successful application of ground penetrating radar (GPR) to nondestructively and continuously measure asphaltic layer thickness and density. Ground penetrating radar surveys were conducted at a five-lane full-scale test site. Each lane is composed of four sections with the same asphaltic mixture but different densities. The GPR signal reflection was used to predict the layer thickness profile. Specific gravity models developed in an earlier study were utilized to predict the asphalt mixture density profile. The GPR-predicted thickness and density were compared to the core-measured values. Results showed that GPR achieved an average relative error of 4.9% in layer thickness measurement without using calibration cores and an average relative error of 2.6% in asphalt mixture bulk specific gravity using one calibration core.

The Rolling Wheel Deflectometer (RWD), which measures pavement surface deflection at traffic speed, offers the potential to characterize the structural conditions of the road network without major delays and in a cost-effective way. The objective of this study was to evaluate the repeatability of RWD deflections and to determine the effects of test speed and pavement conditions on the measured deflections. To achieve this objective, 16 different test sites representing a wide array of pavement conditions were tested. Results of the field testing program determined that the repeatability of RWD measurements was acceptable with an average coefficient of variation of 14% at a testing speed of 32 km/h. The influence of testing speed on the measured deflections was minimal. Since the test speed is restricted by the posted speed limit, testing can be conducted at different speeds while allowing for direct comparison of the measured deflections. RWD deflection measurements appear to properly reflect pavement conditions and structural integrity of the road network by providing for a greater average deflection and scattering for sites in poor conditions.

The objective of this study was to evaluate the performance of asphalt mixtures containing different dosages of recycled asphalt shingles (RAS) using the dynamic modulus (|E*|) test with a universal testing machine and rutting test with the asphalt pavement analyzer (APA). In this study, 5% and 10% RAS were used in the Superpave mixtures. A mixture without RAS was used as the control mixture. All the mixture samples were compacted at 86 gyrations under different temperatures. The 10% RAS had the highest air void level and the control mixture had the lowest air void level. The dynamic modulus and rutting tests were conducted to evaluate the performance of the mixtures with RAS. The results show that the |E*| for RAS mixtures were higher as compared to the control mixture when tested at high temperature (i.e. 39.2°C). Additionally, the added RAS decreased the rut depth significantly after 8000 cycles using the APA.

As transportation agencies search for relief from highly strained budgets, a recent study from National Center for Asphalt Technology (NCAT) shows that hot mix asphalt (HMA) pavements can be designed approximately 18.5% thinner using the 1993 AASHTO Design Guide for flexible pavements. This savings is the result of recalibrating the asphalt layer coefficient. The previously recommended layer coefficient, used by the Alabama Department of Transportation (ALDOT), of 0.44 comes from the AASHO Road Test, which took place near Ottawa, Illinois from 1958 to 1960. The recalibrated average layer coefficient of 0.54 was determined by utilizing performance and traffic data from test sections at the NCAT Test Track, and reflects advancements made in HMA materials and construction over the last 50 years. While the direct savings of 18.5% HMA thickness is obvious, the savings in initial construction and life cycle costs are not as straightforward. However, there will always be a savings in the initial cost and user delay costs because thinner pavements are cheaper to build and take less time to construct. The economic benefits of changing to the new layer coefficient will vary depending upon what layer coefficient an agency is currently using. A survey of state transportation agencies found that there is little consistency in the layer coefficients used across the nation. Many states use different coefficients for varying types of mix or use a different coefficient beyond a certain depth of HMA, while others use the same value regardless of mix type or depth. This inconsistency between the states does not seem to follow a particular trend (e.g., higher values in the southern portion of the country). The wide array of layer coefficients used across the nation suggests that this value needed to be revisited, and has lead many states toward implementing mechanistic-empirical design systems. This paper describes the recalibration efforts at the NCAT Test Track followed by a discussion of life-cycle costs related to using a new structural coefficient. Data from the survey of state agencies are also presented relative to the new NCAT findings and life-cycle cost analysis.

Highway agencies collect pavement condition data over time to manage their network in a cost-effective manner. However, there exist differences among highway agencies for data collection monitoring frequency. While most agencies collect sensor-based data (roughness, rut depth, and faulting) on a yearly basis, image-based data (cracking and other pavement defects) are collected every other year or on a three-year basis. The main reason for the differences is the relative difficulties (cost, resources, and technology) in collecting and processing imaging data. While monitoring frequency has an impact on performance prediction at project-level, it can also affect pavement management system (PMS) decisions at the network-level. Such decisions include identification of project boundaries, optimum timing of pavement fixes, and selection of the most cost-effective pavement preservation strategy. In this paper, PMS data from the state of Washington and MnRoad for flexible and rigid pavements were analyzed to determine the impact of monitoring frequency on the PMS decisions. Results of the analyses show that monitoring frequency may affect the identification of project boundaries, optimum fix type, and timing. These effects have implications on the cost effectiveness of the pavement management strategy.

Thermally induced cracking in asphalt pavements remains to be one of the prominent distress mechanisms in regions with cooler climates. At present, the AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG) is the most widely deployed pavement analysis and design procedure. For thermal cracking predictions, MEPDG utilizes a simplified one-dimensional stress evaluation model with a simple Paris-law (i.e. linear elastic fracture mechanics) based crack propagation procedure. The user-friendly graphical interface for MEPDG makes it an attractive design procedure of choice, however, the over simplicity of the model and lack of a physics-based representation to accurately capture the nonlinear fracture behavior of rate-dependent asphalt concrete reduce(s) the reliability of predictions. This study presents an interactive thermal cracking prediction model that utilizes a nonlinear finite element based thermal cracking analysis engine which can be easily employed using a user-friendly graphical interface. The analysis engine is comprised of (1) the cohesive zone fracture model for accurate simulation of crack initiation and propagation due to thermal loading and (2) the viscoelastic material model for time and temperature dependent bulk material behavior. The graphical user interface (GUI) is designed to be highly interactive and user-friendly in nature, and features screen layouts similar to those used in the AASHTO MEPDG, thus minimizing transition time for the user. This paper describes the individual components of the low temperature cracking prediction software (called LTC Model) including details on the graphical user interface, viscoelastic finite element analysis, cohesive zone fracture model, and integration of various software components for thermal cracking predictions.

The paper presents the application of fractional viscoelastic models to characterize viscoleastic properties of asphalt concrete. This implies the replacement of integer order derivatives in the constitutive equations with fractional derivatives. Integer order stress and strain derivatives lead to exponential relaxation and typically a large number of Maxwell or Kelvin elements are needed to characterize the full viscoelastic response range. In each case, the representation is not unique and the parameters cannot be linked to the composition of asphalt concrete. Fractional models lead to non-exponential relaxation making it possible to characterize the full viscoelastic response range with a small number of elements (typically 1 or 2). As such, the representation is unique and can be linked to the composition of asphalt concrete. Fractional models can also be used to construct the dynamic modulus master curve. As Witczak's sigmoidal model is a simple curve fitting it has no real physical meaning. Fractional models on the other hand have physical meaning, uniquely define the creep compliance and relaxation modulus, and allow better analysis of the physics of the relaxation process by considering the storage modulus, the loss modulus, and the phase angle. Using fractional models to analyze experimental asphalt concrete dynamic modulus results suggested two distinct relaxation processes; one at low temperatures and another at high temperatures. A possible explanation for this behavior can be attributed to the composition of asphalt concrete; at low temperatures, the binder behaves as a viscoelastic solid with aggregate particles more or less securely tied to the binder. The relaxation process is therefore restricted to the binder. At high temperatures, the binder behaves more as a viscoelastic fluid allowing aggregate particles to slide past each other which introduces another aspect of the relaxation process.

The estimation of concrete fracture properties is essential for an accurate cracking prediction of concrete pavement systems. The single-edge notched beam test has been used to characterize fracture parameters of concrete materials in the laboratory, but obtaining a field specimen with this geometry is not always practical. Currently, a standard exists, ASTM D7313, for the measurement of fracture energy in asphalt concrete using the disk-shaped compact tension (DCT) test. The benefit of this specimen geometry for both concrete and asphalt is that it can easily be fabricated in the laboratory or cored from the field. The total fracture energy (G_F) of the material is estimated by using the concept of the work-of-fracture. Additional properties, such as the initial fracture energy (G_f) and the critical crack tip opening displacement (CTOD_C), can be extracted from the same test through employing compliance measurements and the concept of an equivalent elastic crack model. In this pilot study, the DCT specimen is adopted for concrete materials with small changes to the hole and notch geometry and loading rate of the specimen relative to ASTM D7313. The initial DCT experimental results for concrete containing virgin limestone aggregate and recycled concrete aggregate have been consistent and repeatable. A finite element model (FEM) of the specimen was developed to check the published K_IC equation for this geometry and to derive the CTOD_C correction factor. A cohesive zone model was also successfully implemented to simulate the DCT specimen, which verified the validity of the calculated fracture properties from the DCT experiments.

In the last few years cracking in concrete pavements was observed in several highway sections in some regions of Germany. Within the scope of extensive investigations no definite single cause of cracking could be observed in the majority of these cases. Besides incremental load-induced stresses by increasing heavy traffic, within this scope especially load-independent stresses due to hygral and thermal changes are of relevance. Several investigations additionally substantiate reaction products of an alkali silica reaction (ASR). Because of this multiplicity of potential causes for cracking it has not been definitely clarified up to now to which extent especially the ASR contributes to cracking in concrete pavements. Rather it seems that superposition and/or interactions of different mechanisms are responsible.

Using recycled concrete aggregate (RCA) as base/subbase for road construction is alternative way to manage construction waste and reduces the need for virgin aggregates. This paper discusses the long-term performance of concrete pavements on RCA granular layer in comparison to concrete pavements on virgin aggregate granular layer. 18 representative RCA pavement sections across Iowa were primary selected considering state wide location and pavement age. Detailed visual distress surveys were conducted to identify the current pavement surface condition information and the primary distress on RCA granular layer pavement. The pavement information data for the surveyed RCA subbase sections and the corresponding virgin aggregate subbase sections in similar condition were extracted from the Iowa DOT's Pavement Management Information System (PMIS). The performance of the RCA and the virgin aggregate sections was investigated and compared in terms of the pavement condition index (PCI) and the International Roughness Index (IRI). The results indicate that RCA granular layer provides performance compared to the virgin aggregate granular layer in Iowa pavements and are performing adequately.

The transportation network and its supporting infrastructure have significant economic, social, and environmental impacts. Using more sustainable methods to design, construct, and preserve our roads will better protect the environment and meet our ongoing transportation needs. The Minnesota Department of Transportation (Mn/DOT) and our partners in government, industry, and academia have been researching and implementing ways to make our roads greener while maintaining and improving roadway quality. The Minnesota Road Research Facility (MnROAD), an accelerated pavement test facility near St. Paul, MN, is conducting research on several "green" pavement technologies that reduce environmental impacts, reuse roadway materials, or use recycled materials in pavement applications. Green pavement technology should maintain or improve the state of the practice of pavement engineering. This ensures the green product will be market-driven, cost-effective, and sustainable.

Nitrogen oxides (NO_x) emitted from vehicle exhausts are associated with adverse health effects on the public. Self-cleaning, air-purifying concrete pavement is a rapidly emerging technology that can be constructed using photocatalyst such as titanium dioxide (TiO₂). The main objective of this study was to evaluate the environmental effectiveness of TiO₂ coating in photodegrading mixed NO₂ and NO gases from the atmosphere. Results of the experimental program determined that increasing the flow rate and NO₂/NO_x ratio negatively affect the effectiveness of the photocatalytic process. However, within the evaluated range, the titanium content and aggregate gradation had little impact on NO_x removal efficiency. The highest photodegradation rate was observed at 25% relative humidity, which balances the availability of hydroxyl radicals at the surface with NO_x contact with the photocatalytic surface.

Energy harvesting (also known as power harvesting or energy scavenging) technology allows capturing unused ambient energy such as solar, wind, thermal, strain and kinetic, energy of gas and liquid flows and converting the energy into another form of usable energy. The goal of this study was to determine if there is a possibility of capturing thermal energy from pavements and storing the energy and using it as alternative power source to other devices. In this paper, pyroelectric materials have been used as the energy harvester. A single crystal based material called Lithium Tantalate (LiTaO₃), and a polycrystalline composite material based on ordinary Portland cement with carbon nano-fibers have been used as pyroelectric smart materials. The present research indicates that simple material such as Portland cement can be used to capture heat energy from pavements, which can be stored in capacitor for the use of power source to other sensor electronics.

Transportation infrastructure poses significant challenges to sustainable development because its construction and maintenance require large amounts of material consumption, energy input, and capital investment. A refined systematic approach to the design, construction, and management of pavement systems is necessary to meet the objectives of sustainable development. The major components of sustainable development in pavement systems include economic and social considerations in addition to environmental preservation. Asphalt mixture design and construction practices are essential to the environmental component of sustainable development. These practices include, but are not limited to, asphaltic mixture reusing and recycling as well as innovative technologies considering energy efficiency and stormwater management. Performance and durability become a critical issue with the changes introduced to the mixtures. This paper briefly summarizes the evaluation of mixture design practices and the performance of asphalt mixtures prepared with various types of recycled materials and warm mix technologies.

Warm mix asphalt (WMA) appears to allow a reduction in the temperature at which asphalt mixes are produced. This technology is rapidly gaining prominence due to its uniqueness compared with hot mix asphalt (HMA). In this study, the WMA was produced using the foaming method under a simple laboratory setting, and evaluated by the indirect tensile strength and four-point beam fatigue testing. A control mixture, WMA with 1.0%, 1.5% and 2.0% water based of asphalt binder weight were used in the test. These WMAs were produced at production temperatures of 100°C, 115°C and 130°C. The details of the method used to produce the foamed WMA were discussed in this study. Tensile strength and four-point beam fatigue tests were carried out to evaluate the moisture damage and fatigue characteristics of WMA. Generally, when lower production temperature was used, the WMA had higher fatigue potential based on four-point beam fatigue testing. The findings from this study were summarized in the paper.

Fuel consumption costs are influenced by vehicle technology, pavement condition, roadway geometrics, environment, speed, and other factors. The goal of this paper is to investigate the effect of pavement type on fuel consumption. The study has entailed the use of five instrumented vehicles to make fuel consumption measurements over different concrete (PCC) and asphalt (AC) pavement sections. The sections selected have similar characteristics (grade, roughness and texture) and differ only in the type of pavement. The data was collected at three different speeds. The results showed that the difference in fuel consumption between asphalt and concrete pavements is statistically significant at 95 percent confidence level for (loaded) light and heavy trucks at low speed (56 km/h) and summer conditions. Under these conditions, trucks driven over AC pavements will consume about 4% more than if they were driven over PCC pavements. Fuel consumption data for heavy truck in winter was not available. The analysis also showed that the mean differences of fuel consumption between asphalt and concrete pavements for passenger car, van and SUV are statistically not significant for both winter and summer conditions.

Pavement temperature is an important factor of the urban heat island (UHI) effect and it also plays an important role in pavement design. The objective of this study was to compare the pavement temperatures and heat absorbed for nine different pavement sections placed during construction of Phase IV at the National Center for Asphalt Technology (NCAT) Test Track. Temperature probes were installed in each section to measure temperatures at the top, middle and bottom of the asphalt concrete (AC) and three inches into the underlying aggregate base layer. Temperatures were recorded on an hourly basis over a one month period from August to September 2009. Results indicated that an increase in density may also increase pavement temperatures and stored energy. Additionally, changing components or the structure of the asphalt mixture may change its thermophysical properties as well as the amount of energy the pavement is able to store.

This paper documents a research effort conducted regarding chemical stabilization of the naturally wet and problematic clayey soils typically found as subgrade in south Louisiana, and provides detailed information on experiment design, instrumentation, and conducted field and laboratory tests. The objectives of the study include the exploration and development of a methodology to build reliable and conservatively achievable subgrade layers, stabilized with cementitious agents at various field moisture contents so that a treated subgrade layer would not only provide a working table for pavement construction, but can also function as a pavement subbase layer that contributes to the overall pavement structural capacity. The laboratory and field results confirmed that among subbase treatments evaluated, cement-treated soil provided the best-performance followed by lime-treated soil.

Permeable Friction Course (PFC) is a layer of porous asphalt approximately 50 mm thick placed as an overlay on conventional impervious roadway surfaces. The use of PFC improves driver safety due to reduced splash/spray, improved visibility, and decrease in hydroplaning during rainfall events. In addition, PFC improves the stormwater runoff quality from the roadway and has recently been approved as a new stormwater best management practice (BMP) in the State of Texas. However, over time the pore space in the PFC can become clogged with trapped sediment, suggesting a decrease in driver safety and water quality benefits. Therefore, to ensure proper utilization of these benefits, accurate measurement of the drainage properties of PFC is required. In particular, measurement of the hydraulic conductivity is used to determine whether the drainage benefits of PFC are expected to persist. This paper discusses methods for measuring the porosity of core specimens and hydraulic conductivity under non-Darcy flow behavior characterized by the Forchheimer equation. Laboratory and field experimental results of four years of data (2007 to 2010) for three roadways around Austin, TX are presented. The accurate measurement of in-situ hydraulic conductivity using a new nondestructive field test is essential to maintain proper drainage of the PFC layer and to determine when the pore space has become clogged with sediment. In addition, an overview of numerical modeling results of nonlinear two-dimensional flow through PFC is outlined and results are presented in order to properly determine the hydraulic conductivity. Statistical analysis of porosity data show a decrease in porosity with time suggesting clogging of the pore space. Porosity values range from 12% to 23%. However, there has been no observed statistical decrease in hydraulic conductivity with time, suggesting the driver safety and water quality benefits of the PFC layer have persisted after six years of operation. Hydraulic conductivity values on PFC core specimens range from 0.02 cm/s to nearly 3 cm/s. Furthermore, no maintenance of the PFC layer has been conducted during that time.

Three typical Florida Portland cement concrete (PCC) pavement mix designs have been evaluated to capture the input requirements for the new Mechanistic-Empirical Rigid Pavement Design Guide (M-E RPDG). The essential engineering properties were experimentally determined for all required maturity levels, with an emphasis on the coefficient of thermal expansion (CTE) according to AASHTO TP-60 test protocol. Traffic loads, environmental conditions, structural parameters, and analysis/acceptance criteria were defined on account of local requirements. Due to the introduced hierarchy system, nine diverse JPCP models were established and iteratively idealized for PCC top layer thickness. The results demonstrated that cracking is the critical performance criterion for Florida JPCP. Moreover, top-down fatigue damage was isolated to be the controlling failure mechanism. Based on the nine Florida pavement models, a sensitivity matrix was developed to account for CTE as a control variable. Despite wide-ranging PCC, CTE, and thickness properties, clear resemblances were exposed for all scenarios under evaluation. With regard to CTE variation, the JPCP analysis according to the AASHTO M-E RPDG is minimally sensitive to faulting, sensitive to bottom-up damage, and extremely sensitive to top-down damage, cracking, and smoothness/roughness.

The importance of speed and temperature effects on flexible pavement response and performance are well-recognized within mechanistic-empirical pavement design and analysis procedures. While much laboratory testing and some field testing has been conducted to quantify these relationships on traditional mixtures (i.e., Superpave mixes with unmodified or polymer modified asphalt), there has been little investigation until now examining non-conventional materials, particularly in a full-scale test. Nine asphalt concrete (AC) test sections were constructed that included sulfur-modified material, high polymer content, warm-mix asphalt (WMA), high recycled asphalt pavement (RAP) content, Trinidad Lake Asphalt pellets, an open-graded friction course, and a hot-mix asphalt (HMA) control section. The sections were instrumented with an array of strain gauges to measure tensile strain at the bottom of the asphalt concrete. An equation was developed that adequately modeled seven of the nine test sections. The similar response characteristics of the seven sections indicate that they could be modeled in a similar fashion. Laboratory dynamic modulus testing should be conducted to further show how the different materials respond to temperature and speed and to explain why two of the sections did not conform to the model.

Some properties of newly paved Jointed Plain Concrete Pavements (JPCP) are known to influence the long-term performance. The traditional empirical design procedures for JPCP were unable to take into account most of these factors. However, the new Mechanistic-Empirical Pavement Design Guide (MEPDG) accounts for climatic conditions, local materials, selected construction practices, and actual highway traffic distribution. In this study, performance (in terms of International Roughness Index (IRI), faulting, and percent slab cracked) of six typical JPCP pavements in Kansas corresponding to alternative inputs of Portland Cement Concrete (PCC) strength development, PCC shrinkage, and "zero-stress" temperature has been evaluated using MEPDG. The results show that predicted JPCP roughness (IRI) and faulting by MEPDG are not very sensitive to the PCC strength. However, slab cracking decreases with higher PCC strength. In general, PCC shrinkage does not affect predicted IRI. Higher shrinkage strain results in higher faulting. Long term cracking appears to be fairly insensitive to the shrinkage strain. MEPDG-predicted IRI and percent slabs cracked are fairly insensitive to the zero-stress temperature but the faulting is severely affected except on a JPCP pavement section with widened lane and tied PCC shoulder. Percent slab cracked highly depends on the PCC slab thickness. April and October are the best months for JPCP construction (paving) in Kansas.

Due to the continual loading of flexible airport pavements with heavy and wide-bodied aircrafts, it is crucial to consider the impact of aircrafts' tire pressure on pavement damage. The measurements in previous literature have shown that the distribution of tire contact stresses under heavy aircraft is highly non-uniform. Therefore, this study developed a three-dimensional (3-D) finite element (FE) model to investigate the effect of non-uniform aircraft tire pressure on airfield pavement responses. An existing asphalt pavement section at the National Airport Pavement Test Facility (NAPTF) was used in the analysis. The FE model characterized the hot-mix asphalt (HMA) layer as a viscoelastic material and utilized an implicit dynamic analysis to predict the time-dependent pavement responses under moving aircraft tire loading. The tire loading was simulated as a continuously moving load having half-sinusoidal shape distribution along the contact length and non-uniform distribution along five ribs of the tire. The pavement responses (tensile and shear stresses/strains) under various tire pressure distributions were calculated and compared. The results showed that the non-uniform aircraft tire pressure increases the longitudinal tensile strains at the bottom of the HMA layer and the shear strains/stresses in the HMA layer, compared to the traditional uniform tire pressure distribution. The non-uniform contact stresses at high tire inflation pressure resulted in high shear stress near the pavement surface that could cause primary rutting or near-surface cracking; this shows the importance of establishing guidelines for asphalt mixtures stability when used for airfield pavements that support relatively heavy aircraft.

Tar-containing antiskid surface layers are currently used on runways in airfields. They have good adhesion properties and excellent fuel resistance, which make them outstanding compared to other surface layers with bitumen as binder. However, tar-containing products have a high Polycyclic Aromatic Hydrocarbons (PAHs) content. They are toxic and not environmental-friendly. Tar-containing products are not allowed in the Netherlands since 20 years ago, with one temporary exception for antiskid surfaces on runways in airfields. After 2010, it will not be allowed to apply such antiskid layers anymore. For this reason, alternatives to tar containing binders for antiskid runways are strongly required. Before looking into alternatives, the properties of tar-containing antiskid surface layer need to be evaluated and benchmarks should be developed. This paper focuses on the mechanical properties of tar-containing antiskid surface layers. A special Leutner shear test and an advanced pull test were designed to test the shear and tensile strength in the interface between the tar containing antiskid layer and the asphalt mixture layer below. Test results are reported in this paper.

The Federal Aviation Administration initiated a runway instrumentation project in 1992 by installing 460 static and dynamic sensors in sixteen slabs in the take-off area of Runway 34R-16L at Denver International Airport. Static sensors such as embedded temperature and moisture gauges and dynamic sensors such as H-bar strain gauges, LVDTs, and position strain gauges were installed. The investigation was focused on measuring pavement response to aircraft loading and environmental conditions. Currently, the data collection system is severely damaged due to water infiltration and is not operational. Data was collected from 1995 through 1999 which included real-time pavement strains and deflections resulting from aircraft traffic. The slab strain and vertical deflection data was analyzed and compared to three-dimensional finite element model predictions. Overall, good agreement between measured and predicted strains and vertical deflections was observed. This information was used for, among other things, validating and calibrating the structural model in FAARFIELD. An important parameter missing in FAARFIELD is the effect of curling on pavement thickness design. Severe curling can cause premature cracking and incur high maintenance costs. The primary objective of this project is to restore the data collection system to at least measure slab deflections and strains. The future emphasis will be on characterizing slab curling under varying environmental conditions and incorporating it into FAARFIELD. Efforts are underway to restore the data collection system. The entire project is expected to be completed by September 2010. Once resurrected, the instrumentation project will provide valuable slab curling data for updating structural models in FAARFIELD. This paper describes in detail the restoration of the Denver International Airport instrumentation project and the ways in which the FAA plans to make use of the collected data.

A thin concrete pavement wearing surface has been developed using a flowable fibrous concrete (FFC) as a 50 mm (2 in.) inlay on a milled asphalt concrete pavement. The flowable concrete mixture incorporating a hybrid of synthetic fibers was optimized for rapid placement and consolidation. An objective of the wearing surface was to construct reasonable slab sizes and crack widths while ensuring economic feasibility. Laboratory testing demonstrated the FFC has a slump flow diameter value of 400 mm (15.5 in.) and post-cracking residual strength ratio over 47 percent with 0.5 percent volume fraction of synthetic macrofibers. A full-scale demonstration project was cast to evaluate constructability and concrete material performance including placement issues, crack spacing and width development, and interface bonding conditions. Different slab sizes were explored from 1.2 to 3.3 m (4 to 11 ft) with the longer slabs having the earliest and widest cracking up to 1.25 mm (0.05 in.). The joints cracked before day one reside as the largest crack widths measured at later ages. In-situ bonding tests confirmed a good bond between the asphalt and concrete, except in locations where debris from the asphalt layer was not adequately removed.

Cement treated granular materials have been applied for pavement bases and subbases. The availability of prediction models that allow their mechanical properties to be estimated from material parameters like composition and degree of compaction would be extremely useful because it would overcome the need for extensive testing. This paper presents an experimental study on establishing models to estimate the mechanical properties of cement treated mix granulates with recycled crushed masonry and concrete aggregates (CTM_iG_r). Mechanical properties include compressive strength, indirect tensile strength and elastic modulus. Variables influencing the strength and the elastic modulus, such as the ratio of crushed masonry to crushed concrete, the cement content, the water content and the degree of compaction were considered during the mixture preparation of CTM_iG_r. The experimental results show that the compressive strength, the indirect tensile strength and the elastic modulus of CTM_iG_r after 28 days of curing may be accurately estimated on basis of the content of recycled masonry, the ratio of cement to water and the dry density.

Precast pavement technology is a new and innovative construction method that can be used to meet the need for rapid pavement repair and construction. Precast pavement systems are fabricated or assembled off-site, transported to the project site, and installed on a prepared foundation (existing pavement or re-graded foundation). The system components require minimal field curing time to achieve strength before opening to traffic. These systems are primarily used for rapid repair, rehabilitation, and reconstruction of asphalt and portland cement concrete (PCC) pavements in high-volume-traffic roadways. The precast technology can be used for intermittent repairs or full-scale, continuous rehabilitation. As part of the US Strategic Highway Research Program 2 (SHRP 2), a study (Project R05) is underway to develop tools for the design, construction, installation, maintenance, and evaluation of precast concrete pavements. As part of this study, testing was conducted to obtain field performance data from selected precast concrete pavement projects constructed throughout the US. This paper summarizes the field test data collected from intermittent repair projects as well as from continuous application projects and presents the findings of the data evaluation.

Guidelines are being developed to help State Highway Agencies (SHAs) in the selection and design of long life pavements using existing in-place pavements. There is currently very clear design guidance and procedures for designing new long life pavements in terms of new or reconstruction. Guidance that does consider the use of existing pavement is typically directed toward pavement rehabilitation with some determinate life expectancy (ARA, 2004). There is no clear and specific guidance for designing and building long life pavements using existing pavements in place. Using the existing pavement in the design and construction of long life pavements offers numerous advantages both in facilitating rapid renewal of the roadway and in the sustainability aspect of utilizing existing materials. Using the existing pavement significantly reduces the mass movement of materials in and out of the project, and in many cases can facilitate the staging of traffic during construction as part of a cost effective rapid renewal strategy. The approaches found for designing long life pavements using existing pavements presented in the R-23 guidelines are similar to what many agencies currently use, with a few additions from international practice. It was discovered that most agencies use one or more of the approaches contained in the guidelines but have abandoned or no longer consider several of the approaches because of past construction problems. It was found that the assessment of the existing pavement and use of the appropriate design and attention to construction details are critical features of the process. An overview of the form of the guidelines and the detailed information contained in those guidelines are presented, including project assessment, design guidance, critical construction aspects, and guide specifications.

Residential location search has been an interesting topic to both practitioners and researchers. The housing search process starts with an alternative formation and screening practice. At this level households evaluate all potential alternatives based on their lifestyle, preferences, and utilities to form a manageable choice set with limited number of plausible alternatives. This paper attempts to study this screening and filtering practice in more details and to develop a modeling framework that can replicate this process. The average desired property value and work distance are considered as two potential attributes, among others, which are examined by the household to evaluate feasible housing alternatives. It is postulated that alternatives will be included in the choice set only if the average property value meets the household budget and the work distance satisfies the household distance threshold. The search process will then continue until the choice set is complete. A hazard-based model is formulated that can model the desired property value and average work distance together. Several household socio-demographic attributes from eight waves of the Puget Sound Transportation Panel (PSTP) were utilized for model estimation along with built environment variables, characteristics of the supply side of the market, and several other economic indicators. The approach presented in the paper provides a remedy for the large choice set problem typically faced in discrete choice modeling."

Person-to-Person (P2P) car sharing allows car owners to convert their personal vehicles into share cars which can be rented to other drivers on a short-term basis. Using data from the Longitudinal Employment Dynamics (LED) program and the US Census, we develop a methodology to assess the market feasibility of, and economic incentives, P2P car sharing. Further, we apply the methodology to develop a case study of P2P car sharing in Pittsburgh, PA.

The objectives of this paper are to view contemporary traffic congestion as a phenomenon that has always existed within cities throughout history, and to recommend pragmatic modern day solutions to address/manage the congestion problem. This has been achieved by a review of the factors that create congestion, and of the roles that electric streetcars, rapid transit lines, suburban rail lines, and automobiles have played in the decongestion of cities. Examples of outcomes from past transportation improvements are illustrated to show that regional changes in transportation access create new development nodes of activities outside cities that reduce development pressures in the central city (hence reducing congestion growth there) and increase the attraction of peripheral areas to major land developments that lead to increased congestion in these areas. The paper proposes a mix of transportation and land development strategies to minimize the negative effects of urban traffic congestion in the future.

Increasing computing capacity has made possible the use of advanced simulation and optimization methods to solve complex problems in transportation and urban planning. Methods such as linear programming and heuristic optimization have made it possible to find the most cost-effective solution for allocating resources among competing alternatives. Agent based approaches and regional econometric models have succeeded to simulate urban development, economic growth and their impacts across modes of transportation. This paper examines the advantages of incorporating Land Use and Transport Modeling into Asset Management and presents a framework for accomplishing such an objective; especially for timing maintenance, rehabilitation and capital projects to improve safety, mobility and condition. It suggests that decisions for scheduling rehabilitation of existing links and construction of new projects should be based on user impacts and expected gains in terms of regional economic benefits.

The Port Authority of NY & NJ (PANYNJ) is a bistate agency, which conceives, builds, operates and maintains infrastructure critical to the New York/New Jersey region's trade and transportation network. These facilities include America's busiest airport system, marine terminals and ports, the PATH rail transit system, six tunnels and bridges between New York and New Jersey, the Port Authority Bus Terminal in Manhattan, and the World Trade Center. For more than eight decades, the Port Authority has worked to improve the quality of life for the more than 17 million people who live and work in New York and New Jersey - a region that supports 8.6 million jobs with an estimated gross regional product of more than $929 billion. The release of projections for climate change variables published by the Intergovernmental Panel on Climate Change (IPCC) has resulted in greater public awareness and has lead to the launch of state and local government initiatives to evaluate the vulnerability of critical infrastructure. Since PANYNJ facilities are vital to the New York/New Jersey regional economy, their safe and efficient operation is of the utmost importance and an assessment of climate changes impacts was warranted. Many of these facilities are located in close proximity to coastal waters, which further magnifies the potential impacts of climate change variables, such as sustained sea level rise with associated storm surge, increased precipitation and increased temperature. The following case study details the involvement of the PANYNJ in a climate change assessment effort, lead by the New York City (NYC) Mayor's Office of Long Term Planning and Sustainability, between August 2008 and March of 2010. This case study will provide an overview of the evaluation process with an emphasis on the coastal flooding potential and possible adaptation measures.

The Sustainable Airport Manual (SAM) developed by the Chicago Department of Aviation (CDA) established contractual requirements to consider sustainability in the design and construction of every project at O'Hare and Midway International Airports. SAM requires that vegetated roofs be installed on airport facilities wherever possible to reduce the heat island effect, conserve energy, and reduce storm water runoff. The CDA has installed 232,534 ft² of vegetated roofs and is installing 126,456 ft² more (as of November 2010). Installations include the first on-airport Federal Aviation Administration facility in the nation to feature a vegetated roof and the construction of nearly 175,000 ft² of vegetated roof on a major cargo building, one of the 15 largest vegetated roof areas in the U.S. The CDA's installations demonstrate that installing vegetated roofs at airports is practical and cost effective. Operational and maintenance cost savings are expected from increased roof life span, energy use reduction, and storm water quantity/quality management. Additional benefits achieved include a reduction in noise and heat islands, air quality protection, and enhanced aesthetics.

Studies have shown that nation's conventional highways are unsustainable in many aspects. Highways are facing severe challenges, such as deteriorating condition, congestion, energy supply and shortfall of funding for maintenance and capacity expansion to meet increasing demand. At the same time, they consume huge amount of exhaustible natural minerals and energy, and generate waste and emission which deteriorate global environment contributing to climate changes and reduction of the earth's sustaining capacity. Therefore, sustainable highway construction, maintenance and operations have become a prime concern these days. The study examines various research findings and best management practices in road construction industry including some established rating tools for building and some newly proposed tools for road. Finally, it identifies Indicators for sustainable roads for Michigan and develops a sustainability assessment tool to evaluate those indicators that can be expressed as a single comparable index as an end product.

In recent years, with strong economic development and rapid urbanization in China, traffic congestion has become a common phenomenon in urban areas. Focusing on the high-density development of land use in China, the urban population has become highly concentrated and the number of vehicles has also increased exponentially. Traffic congestion problems have become more and more serious in most of the major cities in China. To mitigate the problems, researchers and planners have learned to use a coordinated approach balancing the transportation development and land use. Transit-oriented development (TOD) refers to residential and commercial districts located surrounding a transit station or corridor with high quality service, good walkability, good parking management, and other design features that facilitate transit use and maximize overall accessibility; it is the new fast growing trend in creating vibrant and livable communities. The TOD has become one of the leading urban planning models in China. In this paper, one of the residential and commercial districts in Chengdu, which is the largest city in the southwest of China, was selected for the model study in coordinating the transportation development and land use. The study was based on the TOD model and the genetic algorithm (GA) approach using the MATLAB software. It was shown that the optimal solution significantly increased the density and consistency of the land use when compared with the current construction plan. The traffic flow on the major road of this community was just around 67% of its predicted traffic capacity. The feasibility and effectiveness of the TOD model was verified and recommendations were given for managing the transportation development and land use.

The purpose of this research is to contribute to the body of knowledge on the determinants of walk trips in urban areas using individual data from a large-scale travel survey data. The main purpose of this research is to identify features that can have an influence on the individual decision to walk to travel short distances (less than 1.6 km). Benefiting from the availability of microdata from a large-scale travel survey (2003, sample of some 60,000 households), a study of short trips is conducted for people living in more than sixty districts of the Montreal Area. Walk trip shares are estimated as well as a set of variable describing urban structure (population density, tortuosity of the trip on the road network, intersection density). Using these variables as well as the individual and households attributes, a model describing mode choice for short trips, is estimated at the individual level.

Bangladesh with limited revenues and development budgets falls far of a short of funding to meet current and future transportation needs. Recently, Bangladesh government has taken a fresh public private partnership (PPP) policy initiative to encourage private sector investors in the development of public infrastructures. In light of such a policy, this paper examines the importance of strengthening policies, institutions particularly in handling design/build contract procurements, developing transparent risk allocation mechanisms, and managing projects and programs for successful policy executions. Government institutions must also define overall goals and objectives of projects and explore PPP opportunity in the early development stage of the project to take advantage of not only private investment but also assistance in the planning, designing and building of projects with appropriate skilled manpower and technology for quick and successful implementations of projects.

Efforts to manage highway access are occasionally characterized as inconsistent with livable communities, complete streets and smart growth. One reason is the past emphasis placed on management of vehicular access, which some view as symptomatic of auto-oriented planning and therefore counter to multimodal goals. Another reason is a lack of understanding of the role of access management in advancing sustainable development and supporting walking, bicycling and transit use. This paper explores the role of access management in accomplishing a more sustainable approach to transportation and development planning in the US. Topics include land use and transportation relationships, network planning and activity center strategies, and site design concepts for urban arterial development. Policy changes are suggested.

The Port Authority of NY & NJ (PANYNJ) is a bi-state agency that builds, operates, and maintains infrastructure critical to the New York/New Jersey region's trade and transportation network. These facilities include America's busiest airport system, marine terminals and ports, the PATH rail transit system, six tunnels and bridges between New York and New Jersey, the Port Authority Bus Terminal in Manhattan, and the World Trade Center. For more than eight decades, the Port Authority has worked to improve the quality of life for the more than 17 million people who live and work in New York and New Jersey—a region that supports 8.6 million jobs with an estimated gross regional product of more than $929 billion dollars. Part of working to improve the quality of life for those who live, work, or visit our region is to build, operate, and maintain PANYNJ facilities in a sustainable fashion. As regional transportation agencies work towards meeting sustainability and environmental goals, the US Green Building Council's Leadership in Energy and Environmental Design (LEED®) has become the most common sustainable design standard for facility design, construction, and operations. The LEED model functions well for building-centric projects, but transportation agencies often build, operate and maintain a variety of facility types, including roads, subways, railroads, ports, and airports. Since 2007, the PANYNJ has had Sustainable Design Guidelines with performance metrics that align with those of the LEED Green Building Rating System. These have worked well in guiding staff in new building construction and renovation projects, but they have not provided adequate sustainable design guidance to the majority of the PANYNJ's infrastructure projects. Recognizing a need for more comprehensive guidelines, the PANYNJ's Engineering Department devised additional guidelines specifically addressing sustainable design for transportation infrastructure. This paper presents an overview of the development of these guidelines, with particular emphasis on the case studies examined.

This research seeks to determine the feasibility of decorative concrete overlay (DCO) as an aesthetic treatment for new and existing concrete infrastructure components. The research approach includes exposing DCO-treated concrete samples to various strength and environmental conditions in the laboratory and field. Laboratory testing such as ultraviolet light exposure, flexural fatigue strength, 90-day salt-ponding and 90-day sodium-chloride tank submersion were conducted on two sets of concrete specimens aged 28 days and 125 days. The DCO designs evaluated in the research included a monochromatic-textured brick pattern and a polished multi-tone stone pattern. After 1500 hours of exposure to cycles of moisture and light, the accelerated ultraviolet light exposure showed no visual signs of surface degradation on DCO in terms of fading, color change, lustre, or cracking. The flexural fatigue testing results proved very effective given that the bond between concrete and DCO remained intact under cyclical loading. Also, the 90-day salt-ponding test displayed expected side effects of rusting under their metal embankment walls. Only sections in direct contact with the metal were permanently stained while all other sections were not affected. The sodium chloride submersion brick-designed specimens left behind minor salt-like residues on portions of the surface. Ultimately, the durability, versatility, and ease of application of DCO allude to its viability for aesthetically treating infrastructure.

An emerging automated transit system, PRT can provide exactly the solution that has been sought to create fully walkable sustainable communities. This advanced technology allows for the full integration of walk-ability and the mix of other low tech solutions such as the bicycle. PRT (personal rapid transit) is currently either being implemented — such as at Heathrow airport or in the planning stages linking airport and surrounding transit village concepts such as at Sam Mineta airport in San Jose, California. PRT not only brings a greater level of service to the user due to its point to point movement pattern, but smaller driverless automated vehicles can provide linkages to sustainable energy sources and provide smaller more frequent stations for a fully compact walkable community. This paper shows how this critical balance between machine movement patterns, the built environment and the pedestrian can occur can occur with the application of PRT.

Traffic congestion has many dimensions including intensity, extent, duration and reliability. (1) Conventional congestion analyses use Highway Capacity Manual demand-capacity-delay relationships for assessing performance of specific roadway locations or sections. Broader measures include applying differences or ratios between actual and desired travel times and speeds. (2) Reliability brings a new set of metrics to roadway performance calculations. While typical measures deal with averages, reliability deals with the ranges and distributions of travel times. It focuses on estimating the travel time rates that are not likely to be exceeded. (3) This paper gives some of the key metrics associated with reliability and shows how they differ from conventional congestion analysis. It draws upon and extends recent research efforts.

Motorcycles are a widespread mode of travel in several parts of the world as, for example, in Southern Europe and Asia. However, motorcycle ownership and usage have been scarcely examined, despite being critical for developing transportation and traffic safety plans and policies in urban areas with high motorcycle presence. This pap dels are developed for this purpose based on questionnaires collected in Athens, Greece. A binary Probit model is used for analyzing motorcycle ownership and a hazard-based duration model for explaining factors affecting motorcycle usage. Results indicated that income, gender, age and er investigates factors affecting motorcycle ownership and use; appropriate mo spatial trip characteristic do have an effect on motorcycle ownership and usage.

For the Corridors of the Future project, slip ramps will provide access to trucks between the proposed truck-only lanes (TOLs) and general purpose lanes (GPLs) for trucks to exit using at-grade interchanges. This paper proposes recommendations for slip ramp spacing between the TOLs and the general GPLs along Missouri rural interstate highways using a microscopic simulation model, VISSIM. Simulation of peak period traffic conditions indicated that heavy vehicle speeds were directly proportional to the lengths of the merge, diverge, and link sections. The proposed design recommendations for slip ramp spacing are based on the results of these section lengths. Central composite design was used to generate the cases required for simulation. To ascertain the findings of the simulation study, Level-of-Service for the segments on GPL was determined. This paper provides practitioners and state Departments of Transportation with design recommendations for slip ramp spacing and lengths of merge, link, and diverge for the Corridors of the Future project.

Crashes (in particular, those involving left-turn vehicles) at signalized intersections result in substantial economic losses to the society in terms of death, injury, and property damage. A wide variety of traffic signals are used by the traffic engineers, in the United States, to minimize left-turn crashes and provide maximum safety at signalized intersections. One latest innovation and addition to these traffic signals is the "flashing yellow arrow (FYA)" signal. This paper focuses on safety evaluation of FYA signals "before" and "after" their installation at six selected signalized intersections in the city of Charlotte, North Carolina. Empirical Bayes (EB) technique was used for evaluation. The EB method compares the number of crashes "after" the installation to the estimated number of crashes that would have occurred during the "after" period if the FYA signal had not been installed. Results obtained indicate that the number of crashes would have generally increased if the FYA signals had not been installed at the selected signalized intersections.

This paper introduces and applies an Empirical Bayesian (EB) analysis methodology for assessing highway shoulder paving impacts using Illinois data. Adding new outside paved shoulders is found to be more effective than widening existing paved shoulders and repaving the same width of paved shoulders. Shoulder paving is most effective for multilane highways, followed by two-lane and Interstate highways. Shoulder paving is effective for highways with per lane daily traffic not exceeding 10,000. It is found to be more effective in reducing injury and PDO crashes when the paved shoulder width does not exceed 8ft for Interstate highways and is between 4ft and 8ft for multilane and two-lane highways; and when the combined lane and outside paved shoulder width does not go beyond 20ft. No clear crash pattern is identified among lane widths of 11ft, 12ft, and 13 ft for equal total combined lane and shoulder widths ranging from 12ft to 24ft.

Even though the effectiveness of seat belts is widely known and accepted, seat belt usage remains relatively low in the United States. In addition to the type of seat belt law and associated enforcement practices, there seem to be many driver characteristics and behavior related to non-use of seat belts. Therefore, this study conducted road-user surveys in Kansas with the intention of identifying human factor-related issues that are playing a role in relation to seat belt use. Participation in the survey was completely voluntary even though an effort was made to cover as many groups as possible. Perceptions, attitudes, understandings, stated compliance levels, potential motivators, etc. of road users were obtained through the survey in order to suggest more effective countermeasures to improve seat belt use. Based on identified critical areas, more focused education and training programs need to be developed. In addition, enforcement levels need to be increased, specifically in areas where the most benefit in terms of seat belt usage could be achieved. It was however, interesting to observe that even drivers themselves agree that stricter laws, higher fines, and other penalties are helpful in increasing the self-discipline needed to wear seat belts more frequently.

Free right-turn channels are sometimes used to alleviate vehicle delay at signalized intersections, but motorists often yield unnecessarily when using these channels. To better understand why motorists do not proceed when they have an available path, the authors conducted a national survey. Approximately one thousand survey participants viewed flashcards of intersection treatments and were asked to identify the proper driving behavior from a list of multiple choices. The answers to the questions were compared in Chi-squared cross tabulation analysis. The results showed that statistically significant proportions of people incorrectly indicate that right-turn behavior is similar at standard right-turn pockets or lanes, yield right-turn channels, and free right-turn channels. Men and women were also noted to have statistically different responses. The survey results further indicate that motorists may not distinguish between intersection treatments, prompting better signage and motorist education or the revision of right-turn delay models for different intersection types.

To coordinate signals along a corridor or in a network, the conventional wisdom of using a common cycle length for all coordinated intersections has been widely used and has led to very desirable results. On the other hand, using variable cycle length for this purpose may result in good signal coordination as well, however, the effectiveness and appropriateness of this method remains unknown. In this study, we compare the effects of using a common cycle length, to the effects of using a variable cycle length on signal coordination in a network of oversaturated intersections. For this comparison, we have used our microscopic-simulation-based Intelligent Dynamic Signal Timing Optimization Procedure (IDSTOP) that uses Genetic Algorithms to find near-optimal signal timing parameter in a network of oversaturated intersections. IDSTOP determines near-optimal signal timing parameters on a network of oversaturated intersections with a) fixed cycle length policy, and b) variable cycle policy. In both cases, we have made sure that the network was working at its near-optimal condition. In the first policy, IDSTOP determined a common cycle of 144 seconds and offsets and green splits so that in each corridor the through movements were coordinated. For the common cycle policy, the network processed 4854 vehicles that traveled 482 vehicle-miles, and on average each vehicle experienced 1.27 minutes of delay. The analysis of offsets showed that through traffic movements were coordinated in each corridor of the network. In the second policy, IDSTOP determined cycle length that ranged from 136 to 156 seconds. This shows that the cycle lengths were not similar but the range of that was narrow. The network processed 5298 vehicles, that travelled 501 miles, and the delay was 1.23 minutes. With the variable cycle policy the network processed 8.4% vehicles more than the first policy, vehicle miles travelled were significantly increased, and the average delay per vehicle did not change significantly. The analysis of the offsets showed that through traffic movements were coordinated when needed. These figures show a significant improvement over the traditional common cycle policy. The finding, as an example of other conditions that were analyzed, indicated that using variable signal timing policy results in a considerably higher number of vehicles processed by the network as well as a significantly lower delay in the network compared to a common cycle length.

Wireless magnetometers for vehicle detection were evaluated at a signalized intersection at both stop bar and advance locations. The studied approach had three lanes, and for each lane one sensor was installed at the stop bar and one more at the advance zones. Loop detectors were installed at the same location of the magnetometers and were used as a pointer to identify potential detection errors. Initially, data was collected after the system was installed by the manufacturer. Then, the system setup was adjusted by the manufacturer based on the analysis of the initial data, and data was collected again. Results show that the most frequent error at the stop bar was false calls (5.6%–7.6% due to vehicles in adjacent lanes, and additional 7.8%–9.6% due to single vehicles placing multiple calls), and at the advanced zones it was missed calls (0.9% to 10% per zone). Stuck-on calls and dropped calls were very rare.

There are two objectives for this research. One is to develop an effective procedure to optimize intersection signal timing by minimizing total delay for both vehicles and pedestrians. The second objective is to establish guidance for the pedestrian crossing phase pattern (two-way or scramble) and for the length of WALK phase when a scramble crossing is used. An optimization procedure for signal plans in an isolated intersection was developed. The procedure yielded up to four phases for vehicles with either the two-way or scramble pedestrian crossing phase. A simple Genetic Algorithm (GA) was used in finding suitable signal plans because of the existence of a very large solution searching space. Furthermore, a look-up table was generated to guide the decision between two-way and scramble phases. The guidance considered different combinations of vehicle and pedestrian volumes. Compared with the Highway Capacity Software (HCS) GA function, the proposed procedure has the same accuracy and slightly better capability when pedestrian delay is not considered. However, when pedestrian delay is considered in signal timing, such a comparison could not be made because HCS does not compute delay for pedestrians while the proposed GA procedure does.

Numerous traffic simulation tools are available to assist in the efficient allocation of resources while operating and managing traffic networks. Their model fidelity ranges from detailed (microscopic) to aggregate (mesoscopic) and intermediate (anisotropic mesoscopic), each approach differing in the level of detail of their component demand and supply models. While each tool may have been demonstrated on specific datasets, these data are generally too varied to allow meaningful comparisons of use to practitioners. Objective evaluations of such tools are often lacking, leading to ambiguity about their modeling assumptions, accuracy, feature sufficiency, running time and scalability. In this paper, we apply three popular traffic simulation tools on a common network and demand data. TransModeler (microscopic), DYNASMART-P (mesoscopic) and DynusT (anisotropic mesoscopic) are tested on a real, urban region in Eureka, CA. Their performance over a range of factors are studied, documented and analyzed from both theoretical and empirical perspectives.

Travel time and speed measures on road networks provide key information to identify critical spots of congestion and evaluate the scale of this phenomenon across an urban area. Many technologies are currently available to measure travel time and speed, but each has its limitations. As part of a wider project aiming to develop travel time reliability indicators, this paper presents a comparison and validation of data collected through four different non-intrusive techniques: floating cars, GPS traces, Bluetooth detections and video processing. First, some background information regarding the project and the modeling of travel times and speed on highway networks is provided. Then, a comparison between the various sources of data is presented. Finally, the characteristics of the various data sources are discussed based on the relevance and the availability of the sources.

In this study, link vulnerability index was derived based on a given set of traffic condition and availability of alternate paths when a road link was damaged. The identification results were considered as the basis of traffic assignment. With the purpose of decreasing the system disruption risks, a modified System Optimal (SO) traffic assignment model was presented. The evacuation situations under the conditions of classical and modified SO traffic assignment modes were simulated and compared. The results showed that although the modified traffic assignment mode could lead to an increase in the evacuation network clearance time and average travel time, it could make the system disruption risk decrease about 20%, and the results also provided a useful reference for the urban emergency planning department when making emergency routing strategies.

The growing capabilities of computational tools and the advent of multiple data providing systems have increased the needs and ability to process large sets of microscopic data. Since the data are not directly suited for analysis or modeling, they are often stocked without further question, while they could shine a new light on critical traffic phenomena such as congestion. This research is a spin-off of a project on the modelling of travel time reliability on highway corridors. The project relies on floating cars data but has also led to the exploration of historical incidents datasets that required various pre-processing steps. A visualization tool was developed using Microsoft Excel in an innovative way. This paper reports on the development of this tool that provides some insight into the analytical potentialities of the incident databases. Four years of data are examined and converted into usable information through cross-examination and interactivity.

This study evaluated the speed compliance with the posted speed limit both quantitatively and qualitatively using objective and subjective data analysis. Free flow speed data for three work zones on I-44 in Missouri were used for the objective evaluation. Speeds analyzed for cars and trucks were distributed normally. Construction activity had a significant effect in reducing the speed of vehicles. Results indicate that the speeds of vehicles were statistically higher than the speed limit regardless of the construction activity, when the lane width was not reduced. The subjective evaluation investigated the drivers' perception of driving through the work zone by using a survey questionnaire. About 40% of drivers indicated that the speed of other drivers were less than the speed limit which contradicted the results of the objective analysis. More than 70% of drivers experienced delay and more than 90% agreed that construction activity reduced their speed which was ascertained from the results of the objective analysis.

Determining the effects of Speed Photo-radar Enforcement (SPE) on headways of vehicles traveling in a work zone is important since maintaining a larger headway provides drivers with a longer time to avoid a potential rear-end collision. In addition, when the headway between two vehicles is less than the follower's reaction time, a rear end collision is likely to happen if the leader suddenly decreases its speed. In this paper, the effects of the SPE on the headway of vehicles traveling along a work zone are studied. For this purpose, we collected data from two locations that were around 1.5 miles apart in a work zone on interstate highway 55 at. The SPE van was present at the upstream location. The headway of all vehicles within a period of 45 minutes was measured at the upstream location as well as the downstream location. The results of this study showed that the presence of the SPE did not reduce the headway of the traffic stream at the location that it was present, as well as at the downstream location. This was confirmed by comparing the headway of followers (headway less than four seconds) when the SPE was deployed in the work zone to the headway of them when the SPE was not present, for both lanes combined, and for the shoulder and median lanes separately. The same result was observed for different pairs of leaders and followers. In addition, our analysis showed that the SPE prevented a reduction in the headway of car-car pairs traveling on the median lane at the downstream location.

Roundabout intersections, increasingly used in the U.S., sometimes incorporate slip lanes to facilitate right-turning traffic flow and reduce delay, thereby increasing capacity and safety. Performance of a single-lane roundabout with an adjacent slip lane is modeled with the SIDRA Intersection analysis tool for three types of slip lane: free-flow, yield, and stop, and is compared to having no slip lane. The gap acceptance-based assessment considers four experimental traffic percentage distribution matrices representing flow scenarios. SIDRA results confirm that average delay and circulating conflict volumes in a roundabout with a slip lane are related exponentially to slip lane volumes. A free-flow slip lane exit type helps to reduce total average delay in the roundabout and the slip lane approach. Both yield and stop slip lane exit types also reduce roundabout total average delay but to a lesser degree than a free-flow slip lane. Finally, theoretical capacity threshold values for slip lane volumes are estimated to range from 150 to 350 vehicles per hour for traffic volume distribution scenarios.

Conventional treatment of left-turn at major arterial intersections is often found to be the major cause of poor arterial operations, especially under a heavy volume condition. New Jersey Jug-handle Intersection (NJJI), an unconventional intersection scheme, eliminates direct left turn and has been in place on NJDOT heavy-volume arterial roadways for quite a long time. The NJJI scheme separates left turn vehicles prior to or after crossing the intersection via a right side jug-handle (forward or reverse) ramp and then allow them to make turn onto cross-street via ramp terminus separated from the main intersection. By introducing jug-handle ramps at all four approaches of a four-legged intersection, four identical ramp termini can be constructed. These ramp termini can be signalized along with the main intersection and each of them can be operated on a two-phase signal. CORSIM, a micro-simulation model, has been utilized to evaluate and compare the operational performance of a forward ramp NJJI scheme (with and without signals at the ramp termini) with a conventional intersection (CI) scheme. The simulation study reveals that the NJJI scheme with pre-signals significantly improves traffic operations while increasing the intersection capacity. Other benefits of the NJJI scheme include reduction of vehicle stop time, fuel consumption and emission level.

Road intersections are dangerous places in the road system due to the high number of conflicting points between motorized and non-motorized vehicles. In the case of defined traffic volume, several research groups have proven that roundabouts reduce the number of injuries and fatal accident cases. In the last years, several studies have investigated the performance of roundabouts, among which, include different models with the ability to calculate the entering flow (Qe) as a function of the circulating flow (Qc). This research work has focused on an analysis of the performance features of Italian urban roundabouts, that have non-standard geometric characteristics. The goal of the research work is to analyze, on the basis of geometrical and design parameters, the capacity of the "non-standard roundabouts" in order to understand in which way non-standard features influence capacity. The study underlines that in standard roundabouts the entering flow is reduced when the circulating flow increases (like in the existing international models) and in non-standard roundabouts the entering flow is not reduced when the circulating flow increases (it seems that there is not a relationship between circulating flow and entering flow).

Several factors of freeway mainlines, exit ramp sections, and cross-roads, such as geometric design, environment, vehicle/driver characteristics, and traffic features, may have significantly impacts on crash injury severity at freeway exit ramps. Freeway exit ramps are defined as the sections from the painted nose to the ramp terminal, and provide limit accesses from freeway mainlines to cross-roads. To explore the impacts and address the significant factors, injury severity prediction models was developed in this paper using three regression technologies: Ordered Probit, Partial Proportional Odds, and Heterogeneous Probit. The analysis results showed that ramp configuration (Diamond, Free-flow Loop, Outer Connection, and Parclo Loop) has significant impacts on crash injury severity at exit ramp sections. Diamond ramp is safer than other configurations while Outer Connection seems to increase crash injury severity than other ones. Other significant factors include lane configuration, channelization at ramp terminals, distance between ramp terminal and the first intersection on crossroads, speed limit on ramps and mainlines, shoulder width on ramps, and alcohol/drug involvement.

Work zone crashes have accounted for 9,900 fatalities in the United States in the last ten years. As the traffic demand on the highways is increasing, management of such traffic flows in work zones has become a challenging task for many highway agencies and understanding crash characteristics would be valuable for highway agencies in setting up proper traffic management plans at work zones based on the prevailing conditions. Accordingly, this study investigated characteristics of work zone crashes in Iowa, Kansas, Missouri, Nebraska and Wisconsin, states currently included in the Smart Work Zone Deployment Initiative (SWZDI) region. Work zone crash data were obtained from respective departments of transportations and crash data from years 2002 to 2006 were considered in this study. The characteristics related to work zone crashes such as environmental conditions, vehicles, crashes, driver, and roadway factors were analyzed for the combined states. Results showed that most of the work zone crashes occurred under clear environmental conditions as during daylight, no adverse weather, etc. Multiple-vehicle crashes were more predominant than single-vehicle crashes in work zone crashes. Primary driver-contributing factors of work zone crashes were inattentive driving, following too close for conditions, failure to yield right of way, driving too fast for conditions, and exceeding posted speed limits within work zones. Middle aged drivers were more involved in work zone crashes and most of the work zone crashes lead to Property Damage Only (PDO) crashes. In order to find the relation between crash severity and other variables a test of independency was performed between them using chi-square test methodology.

Work zone safety has become a major concern to many highway agencies and the highway safety community is looking at various ways of improving the situation. Accordingly, this paper describes an application of ordered probit modeling methodology to identify the factors associated with the injury severity of work zone crashes using a state level dataset. According to the findings of the severity model, work zone crashes involving trucks, following too close, non deployment of airbags, sideswipe collision of the same direction vehicles, crashes occurring on roadway, and crashes occurred while vehicles were taking left/right turns in work zone area are some of the factors that are contributing towards higher injury severity in work zone crashes.

The focus of this paper is to develop models to estimate the number of crashes at intersections. Data collected at 150 intersections in the City of Charlotte, North Carolina were used in the development of models. Factors such as demographic (population and households), socio-economic (income and employment), network (number of lanes, speed limit, signalized or not, skewed, number of left-turn and right-turn lanes and traffic volume by turning movement) and land use (commercial and residential) characteristics at each intersection were considered as independent variables. The numbers of crashes at each intersection was used as a dependent variable. Generalized linear models were developed to estimate risk at intersections. The role of spatial proximity in capturing data to develop models was also examined. These models provide valuable insights on characteristics that contribute to crashes at intersection. They could be used by practitioners to estimate potential risk at new intersections and at intersections near new developments so as to proactively apply appropriate treatments.

Most of current intersection vehicle crash models are calibrated using global regression analysis methods that are often inaccurate in crash predictions as some localized crash contributing effects are not explicitly addressed. This paper employs the Geographically-Weighted Regression (GWR) technique to calibrate statistical models for predicting intersection injury, property damage only (PDO), and total crashes using data on 245 intersections in City of Chicago for period 2001–2008. In the calibrated GWR models, factors contributing to intersection vehicle crashes identified include major and minor road daily traffic, number of major and minor road through and left-turn lanes, and household income level. The analysis of variance (ANOVA) test reveals that improved model predictability is achieved from all crash models developed using the GWR technique compared with those models calibrated based on the Ordinary Least Squares (OLS) technique. The Monte Carlo test identifies significance of spatial variability of explanatory variables in the GWR models.

Of the 41,059 motor vehicle fatalities in 2007, 12 % or 4,808 died in crashes that involved a large truck, but, only 17% of those fatalities were occupants of large trucks. Although large trucks contributed to only 3% of registered vehicles and 7% of vehicle miles travelled in the last 5 years, their impact in terms of severity proves to be a major concern especially for non-truck vehicle occupants. Fatal crash data from the Fatality Analysis Reporting System (FARS) was used to study this issue and to identify factors contributing to truck-involved crashes. Driver, vehicle, and crash-related contributory factors were identified, and the likelihood of occurrence of these factors in truck-involved crashes with respect to non-truck crashes was evaluated using the Bayesian Statistical approach. The most critical factors showed that likelihood ratios for factors like stopped or unattended vehicles, improper following, defective brake system, and vehicle being set in motion by a non-driver have greater probability of occurrence in truck crashes than in non-truck crashes Several other factors such as cellular usage, inattentiveness, and failure to obey traffic rules have been identified as more likely contributory factors for fatal truck crashes. By addressing these factors through the implementation of appropriate remedial measures, the overall truck crash rate can be reduced, which can help in improving overall safety of the transportation system.