High-occupancy toll (HOT) lane operation has been implemented in several urban areas in the United States and is regarded as one of the most effective management strategies against freeway congestion. By allowing single occupancy vehicles (SOVs) to pay a toll for using high-occupancy vehicle (HOV) lanes, the excess capacities of HOV lanes can be used and the overall traffic mobility of the roadway section can be improved. However, research on HOT lane operations is still in its early stage. A series of theoretical and practical issues on optimizing HOT lane system performance particularly require immediate attention for better practice. Simulation-based investigation on HOT lane operations provides a cost-effective, risk-free, and prospective means of exploring and addressing these issues. A microscopic traffic simulation tool, VISSIM, is exploited in this study. By overcoming functional constraints with the VISSIM built-in modules and taking advantage of its component object model interface, we develop a new external module to enable HOT lane simulation. This HOT lane module provides additional flexibility to satisfy any specific demands from particular researchers and practitioners. Based on this external module, HOT lane operations can be simulated and evaluated as demonstrated using the Washington State Route (SR) 167 HOT Lane Pilot Project. The SR-167 simulation results not only quantitatively evaluate the overall system performance but also identify potential problems. Significantly different operational performance was illustrated between HOV lane and HOT lane systems using the developed simulation models. The simulation platform used in this study has the potential to be a cost-effective evaluation tool for HOT lane operations.

Two continuous statistical distribution models, gamma and lognormal, are proposed for desired time gap $\left(T_X\right)$ and time headway $\left(T\right)$ of drivers in a steady car-following state on two-lane roads under mixed traffic conditions. A simulation program was developed for traffic movement on two-lane roads incorporating actual behavior of mixed traffic in terms of speed, placement, arrival pattern, and overtaking behavior. The program was run at 50/50 directional distribution with varying traffic composition and volume level. Headway data obtained from simulation runs are analyzed to develop a relationship between the desired time gap $\left(T_X\right)$ and the speed of the vehicles for five categories of vehicles, namely, car, heavy vehicle, motorized two-wheeler, three-wheeler, and tractor. It is observed that the desired time gap of a two-wheeler is the minimum of all other categories of vehicles. It is due to their better maneuverability, which allows them to maintain shorter gaps. The desired time gap for tractors is the maximum of all vehicles, which is due to their low acceleration capability and poor braking efficiency. These relationships will be extremely useful in developing the microsimulation models of traffic flow on two-lane highways.

Numerous factors may contribute to high-severity crashes in highway work zones. Identifying these factors and then alleviating their impact is a challenging task that traffic engineers and researchers have to confront. In this study, the work zone risk factors that could increase the probability of causing fatalities when severe crashes occur were examined using a comprehensive approach. The researchers first identified the significant risk factors based on a screening process that incorporates both statistical analyses and empirical research findings. They then systematically investigated these factors using logistic regression and frequency analysis techniques. The severe crashes including the fatal crashes between 1998 and 2004 and injury crashes between 2003 and 2004 in Kansas highway work zones were used in the study. The assessed risk factors included variables describing driver characteristics, environmental conditions, crash road conditions, and other crash information. The results of this study will help traffic engineers to understand these risk factors and how the factors could increase the likelihood of having fatalities when a severe crash occurs in a work zone. Consequently, effective safety countermeasures may be designed at the work zone planning and installation stages to prevent safety deficiencies.

Providing locally elected officials with reasonable information about the cost of maintaining and improving an unpaved road network is part of the job for those directly responsible for maintaining such a network. This paper describes a simple method for generating estimates of the annualized maintenance and construction costs incurred by small agencies, three Wyoming counties in this case. Several simple inputs are used to estimate the total annualized cost of operating an unpaved road network. Road segments are assigned to one of four functional classes. Treatment costs and frequencies are determined for each functional class. These inputs are used to generate annualized network-level cost estimates for each county. The most difficult aspect of this procedure is generating reasonable treatment cost and frequency information, particularly for rehabilitation and reconstruction costs. The process of generating these inputs, along with the process of assigning roads to functional classes, is described in this paper. Comparisons between the estimates generated using the method presented in this paper and actual costs incurred by two of the counties both demonstrate the feasibility of this method and highlight aspects of this procedure that will benefit from further refinement. Tailoring treatment costs and frequencies to in-place cost tracking methods will make for more precise projection of future costs, particularly for maintenance tasks. The methods presented here are particularly useful for smaller agencies without the resources to undertake highly sophisticated, expensive asset management programs. This methodology may be applied to a wide and diverse range of agencies.

A review of the experience of 23 states on the use and effectiveness of cable median barriers is presented. As of 2007, 23 states have installed more than 4,183 km (2,600 mi) of cable median barriers. Experiences of the pioneering states, such as New York, Missouri, Washington, Oregon, North Carolina and Arizona that initiated the utilization of cable median barrier in the United States are included in this paper. Results of the review show that the use of cable median barriers in depressed medians with moderate slopes had a significant effect on the reduction of cross-median crashes in many states. While these results are encouraging, occasional fatal crossover crashes penetrating the cable barrier still demand attention and improved techniques or procedures for selecting or locating cable median barrier will continue to evolve.

Speeding behavior is a complex problem that requires a full understanding of drivers’ attitudes and beliefs. Such understanding could lead to effective design and robust interventions to improve the speeding behavior of drivers. In this article, the attitudes and beliefs of a sample of 402 drivers from Al Ain are analyzed using the framework of the Theory of Planned Behavior as a reference. Al Ain is the fourth largest city in the United Arab Emirates, located about 120 km from Dubai. A multiple regression analysis was applied to assess the relationship between self-reported speeding behavior and the drivers’ attitudes and beliefs. The results indicated a significant association between the attitudes and beliefs and self-reported speeding behavior. The attitudes and beliefs were also explored in the context of the demographic characteristics of the drivers. This study recommends strengthening law enforcement by particularly increasing police patrols and introducing tougher speeding fines in Al Ain to reduce excessive speeding. Other alternatives such as awareness campaigns for building drivers’ awareness might yield long-term positive influence on driver attitudes and beliefs about speeding. However, these alternatives would take time, and, without the presence of tighter speed controls through law enforcement, such awareness campaigns may not be very effective.

Cast iron pipe came into heavy use during the latter half of the 19th century and numerous utility companies formed extensive pipeline networks using cast iron pipes until 1940s. Later cast iron pipe was superseded by ductile iron pipe. The existing cast iron pipelines have been in service for a long period of time, with some of them being more than a century old. While many of the existing cast iron pipelines remain perfectly serviceable, some of them show signs of deterioration, mainly in the form of breaks and leaks. The deteriorated cast iron pipe sections are currently being replaced with polyethylene pipes. When the polyethylene pipes are exposed to temperature drops, higher thermal expansion/contraction coefficient of polyethylene results in additional pullout forces in the cast iron pipes. Depending on the magnitude of the temperature change and the resisting forces available, such as soil-cast iron interface friction, the additional forces can cause cast iron pipes to pullout from the joints resulting in leaks. A series of full-scale field tests were performed to determine the pullout resistance of cast iron pipe. The tests were performed for two types of backfill densities, dense and loose. Pullout resistance-displacement relationships were obtained for both cases. The test results were compared with a model available and used in practice for the calculation of pullout resistance of buried pipes.

The present study formulated a three-dimensional (3D) vehicle-pavement coupled model to simulate the pavement dynamic loads induced by the vehicle-pavement interaction where both the vehicle vibration and pavement deformation were considered. Based on this model, the effects of road surface conditions, vehicle parameters, and driving speed on pavement dynamic loads were analyzed. The impact factor, dynamic load coefficient, and frequency distribution of pavement loads were mainly concerned in this study. The simulated results indicated that under rough road conditions the dynamic loads of vehicles are significantly higher than the static loads. The developed methodology can be used to further study the vehicle-induced pavement response, and the loading information will be useful in analyzing vehicle-induced pavement damage.

This paper presents an analytical approach for estimation of temperature stress in asphalt pavements. Nonlinear variation of temperature with respect to time as well as across the depth of the asphalt layer is considered. The derived stress profile is used to estimate the low-temperature crack spacing. The estimated crack spacing is found to compare well with that of observed in the field. The proposed approach has been illustrated through a numerical example.

At a certain point in the life of a flexible pavement, rehabilitation is required to improve pavement condition and to defer reconstruction. Pavement managers seek the best rehabilitation treatment on the basis of cost effectiveness. Using 1994–2002 data from a wet-freeze mid-Western state in the United States, this paper analyzes the cost effectiveness of four flexible pavement rehabilitation treatments: functional hot-mix asphalt (HMA) overlay, structural HMA overlay, resurfacing (partial 3R standards), and mill full-depth and asphaltic concrete overlay. The performance indicator used is the international roughness index and treatment effectiveness is measured in terms of performance jump (short-term), and service life and increase in pavement performance (long-term). The treatment cost is the equivalent uniform annual cost per lane-km incurred by the agency and user; and cost effectiveness is the ratio of effectiveness to cost. The study estimated treatment effectiveness under various combinations of traffic loading and climatic condition, and initial pavement condition. The results suggest that in the short-term, HMA structural overlay is the most effective treatment. For the long-term, the results are equivocal: HMA structural overlay is most effective from the perspective of average performance over the treatment life; resurfacing (partial 3R standards) is the most effective from the perspective of treatment service life. With regard to cost effectiveness, however, the results were consistent: for all three measures of treatment effectiveness, mill full-depth and asphaltic concrete overlay unequivocally appears to be the most cost effective treatment. Finally, the paper recommends that cost effectiveness analysis should be accompanied by a candid deliberation of project constraints, the local environment, and agency practices.

Nanotechnology is the term used to cover the design, construction, and utilization of structures with at least one dimension measured in nanometers. Compared with typical civil engineering structures, the two fields operate on hugely divergent dimensional scales. Nanotechnology initially developed in the fields of physics and chemistry, and most fundamental developments still occur in these fields. However, for the technology to affect society at large, it needs to be applied in areas such as the engineering field. This paper focuses specifically on current and potential developments in pavement engineering where the unique properties of nanomaterials may be used to deliver a better environment to society, based on identified needs and challenges in the pavement engineering field. It is demonstrated that there are essentially two areas where nanotechnology can complement pavement engineering. These are in the development of improved materials and the use of characterization methods to improve the understanding of materials. Examples of current and planned research in these areas are cited and discussed. Finally, current challenges in exploiting the unique properties of nanomaterials in pavement engineering are indicated and discussed. The paper demonstrates that although the majority of the fundamental developments in nanoscale science and technology are occurring in the fundamental physics, chemistry, and typically electronic engineering fields, the potential for this technology to impact on the quality of life of society at large is huge.

Two types of analysis were conducted to examine the impacts of midcentury scenarios of anthropogenic climate change on flexible pavement infrastructure in southern Canada. An analysis of deterioration-relevant climate indicators at 17 southern Canadian sites revealed that over the next 50 years low temperature cracking will become less problematic, structures will freeze later and thaw earlier with correspondingly shorter freeze season lengths, and higher extreme in-service pavement temperatures will raise the potential for rutting. Pavement performance simulations conducted using the mechanistic-empirical pavement design guide and data from the Canadian long term pavement performance program for six of these sites also suggest that rutting issues will be exacerbated by climate change and that maintenance, rehabilitation, or reconstruction will be required earlier in the design life. While the simulated effect of climate change was found to be modest, both in absolute terms and relative to variability in pavement structure and baseline traffic loads, pavement engineers would benefit by incorporating longer time series of weather and climate in their designs. Although the analysis was conducted for southern Canada, many of the findings and impacts may be similar for the northern United States.

In this paper, we propose an algorithm for an upgrading arc median shortest path problem for a transportation network. The problem is to identify a set of nondominated paths that minimizes both upgrading cost and overall travel time of the entire network. These two objectives are realistic for transportation network problems, but of a conflicting and noncompensatory nature. In addition, unlike upgrading cost which is the sum of the arc costs on the path, overall travel time of the entire network cannot be expressed as a sum of arc travel times on the path. The proposed solution approach to the problem is based on heuristic labeling and exhaustive search techniques, in criteria space and solution space, respectively. The first approach labels each node in terms of upgrading cost, and deletes cyclic and infeasible paths in criteria space. The latter calculates the overall travel time of the entire network for each feasible path, deletes dominated paths on the basis of the objective vector and identifies a set of Pareto optimal paths in the solution space. The computational study, using two small-scale transportation networks, has demonstrated that the algorithm proposed herein is able to efficiently identify a set of nondominated median shortest paths, based on two conflicting and noncompensatory objectives.