This paper presents a mechanistic-empirical framework for evaluating permanent deformation in flexible pavements. The procedure uses rational material properties and can be used as an analysis tool, as a companion to the design method. The material properties required are (1) the stress dependent modulus of the pavement layers, asphalt concrete and granular base/subbase, and (2) the relation between the accumulated and the resilient strain with the number of load repetitions and stress level. The procedure is a compromise between simple and advanced approaches, between linear elasticity and nonlinear incremental finite element approaches. In addition to this improvement, the proposed procedure uses the “actual” temperature distribution in the asphalt layer at every hour in the whole design period. It is evaluated by computing the rut depth in well-designed pavements. All the results for the pavement response under different conditions are within the expected ranges.

Seal coating is a preventive maintenance technique typically applied to low volume asphaltic concrete pavements to defer the need for major rehabilitation. Past research on seal coating effectiveness has generally indicated that both short- and medium-term benefits are associated with this treatment. Regarding the relationship between short-term effectiveness and initial pavement condition, results of past studies have been equivocal: some studies found that lower levels of initial pavement condition are associated with lower effectiveness after seal coating treatment, while results of other studies were to the contrary. This paper, in developing seal coating effectiveness models, explains the findings of both schools of thought. The paper finds that the direction of seal coating effectiveness in relation to the initial pavement condition depends on the measure of effectiveness used: pavements in relatively poor condition were generally associated with higher performance jumps but lower reductions in their rates of deterioration. This implies that the greater benefits of seal coating on relatively good pavements, compared to relatively poor pavements, are observed particularly when considered over an extended period of time. On the other hand, pavements in relatively good condition were generally associated with lower performance jumps but greater reductions in their deterioration rates. In the course of the study, the paper selects appropriate measures of seal coating effectiveness, calculates values of each measure using data on Indiana pavements that received this treatment, determines the statistical significance of such effectiveness values, and finally estimates seal coating effectiveness as a function of pavement and/or treatment attributes. In the computation of effectiveness values, due cognizance is given to the critical issue of relative timing between the application of the seal coating treatments and annual performance monitoring.

An integrated pavement management system has been designed to provide the pavement engineers with an effective decision-making tool for planning and scheduling of pavement maintenance and rehabilitation (M&R) work. The developed system applies a discrete-time Markovian model to predict pavement deterioration with the inclusion of pavement improvement resulting from M&R actions. An effective decision policy with two major options has been used. The first option optimizes a generalized nonlinear objective function that is defined in terms of proportions of pavement sections in the five deployed condition states, and is subjected to budget constraints. The second option minimizes M&R cost which is subjected to preset pavement condition requirements in terms of state proportions at the end of a selected study period. The system applies two approaches for the selection of pavement project candidates. The first approach is based on random selection of pavement sections within the same condition state, while the second one relies on worst-first selection within the same condition state. The optimization process is performed using two different optimization methods which are the penalty function method and uniform search method.

Due to the large variety in aircraft types and loads, the use of a comprehensive rating system for the aircraft loads and the bearing capacity of the pavements has been an obligation of airport authorities. Among the major features of such classification systems is their relation to the structural performance and the bearing capacity of pavements. However, implementation of today’s official rating system, the aircraft classification number–pavement classification number developed by the International Civil Aviation Organization, has shown that in many cases, it is difficult to incorporate the information given by modern procedures currently used for the analysis and evaluation of performance of airfield pavements. The reporting often fails to reflect the actual bearing capacity of the pavement within the high standards set by several modern approaches used for airport pavement design and evaluation. In this work, an attempt to improve the correlation of pavement strength reporting with the bearing capacity is presented and discussed.

The design of buried flexible pipe involves checking for load-induced deflection, buckling strength, strain or stress under internal pressure, strain or stress from combined loading, and handling stiffness. Most of these design checks involve using the design parameter commonly referred to as the modulus of soil reaction, $E^{\prime }\text{.}$ Despite the fact that modified Spangler’s equation has been around for over several decades, few engineers in practice even know how this $E^{\prime }$ is defined let alone how to obtain a proper value for it. The most popular form for $E^{\prime }$ comes from the empirical data published by the U.S. Bureau of Reclamation and most consensus standards carry these values despite its numerous shortcomings. The irony is that the U.S. Bureau of Reclamation knew that their data were providing values of $E^{\prime }$ varying several hundred percent from a mean value, yet, never even considered other factors that would be significant in explaining their unreliable $E^{\prime }$ values. The pure simplicity of the U.S. Bureau of Reclamation values led to these being in use in the hands of the pipe supplier and never its engineering soundness. The purpose of this paper is to start from the fundamental pipe–soil interaction principles and geotechnical engineering and build the engineering know how needed to establish $E^{\prime }$ values on a project-specific basis allowing for most significant factors. A step-by-step methodology is presented.

Daily traffic assignments to a large-scale road network are described for build and no-build scenarios to evaluate the addition of two proposed ramps between I-295 and SR-42 in the New Jersey part of the Delaware Valley region. The road network consists of 39,800 links connecting 1,510 zones. The user-equilibrium traffic-assignment problem was solved with a new algorithm called origin-based assignment (OBA), which can achieve highly converged solutions with reasonable computing effort. Following a description of the user-equilibrium traffic-assignment problem and the OBA algorithm, the stability of link-flow differences between the two scenarios in the vicinity of the proposed ramps are examined over a broad range of assignment convergence levels. Then, link-flow differences over this range of convergence levels are compared to link-flow differences between two very highly converged solutions. Examination of the findings reveals, in the writers’ view, that a relative gap of 0.01% (0.0001) is required to ensure that the traffic assignments are sufficiently converged to achieve link-flow stability. These convergence levels are then interpreted in terms of the number of Frank-Wolfe iterations needed to achieve comparable relative gaps as well as the computational effort required.

Transit travel time and operating speed influence service attractiveness, operating cost, and system efficiency. The objective of this paper is to estimate the values of parameters that affect the total travel time for a particular bus route in Portland, Oregon. The Metropolitan Transportation District of Oregon (TriMet) provides transit service in the three-county Portland metropolitan area. TriMet has implemented a Bus Dispatch System (BDS) as a part of its overall service control and management system. This BDS provides a rich array of archived data that were used in this study to develop the trip time model for the route under study. This trip time model provides heightened understanding of the factors that affect the trip time on the route. The value of the model was revealed when sensitivity analyses were performed using data from the studied route. This analysis concluded that improvements can be readily achieved after understanding the factors that affect total trip time. Finally, some conclusions and recommendations are presented and suggestions for additional research are provided.

Right turn plus U-turn at median openings as an alternative to direct left turn has been considered important issue in access management. The motivation behind using this strategy comes from the consideration of safety as well as from traffic operational performance. The objective of this study was to evaluate the operational performances of direct left turn and right turn plus U-turn through simulation. This study attempted to figure out under what traffic conditions replacing a direct left turn with a right turn plus U-turn would be beneficial from an operational point of view. CORSIM, a combination of FRESIM and NETSIM, was selected as the analytical tool in the study due to its strong capability in road network evaluation and its animation display function. A total of six sites were selected to do the field data collection. The delay and travel time were used as the measures of effectiveness (MOE) in evaluating the operational performance of direct left turn (DLT) and right turn plus U-turn (RT+UT). The site-specific simulation models for the six sites were developed using CORSIM. Each model was calibrated based on the field data. The comparisons between DLT and RT+UT in terms of the delay and travel time have been conducted under different levels of traffic volume. The simulation results showed that, with an increase in the through-traffic volume on the major road, the delay as well as the travel time of DLT were higher than those of RT+UT. This information is very useful for decision makers in determining what kind of median opening will be applicable under the given traffic conditions.

The purpose of this research was to develop a model for estimating roundabout delay as a function of the influencing traffic and geometric factors. Fourteen roundabouts were selected from different cities in Jordan. Circulating volume, entry volume, and entry delay were measured during peak and off-peak periods using video cameras. Data on geometric design elements including circulating width, entry width, and roundabout diameter were measured through field survey. An empirical approach was used to develop a delay model as a function of the influencing factors based on a time interval of 15 min. The analysis indicated that geometric variables have significant effects on the roundabout entry delay. The entry width has the greatest influence, whereas the circulating width has the least influence. A comparison between delay models produced using different time intervals showed that, as time interval increases, $R^2$ increases. The SIDRA delay model was validated using the field delay data, and it was found that it overestimates the delay, especially at high delay ranges. The M/M/1 (random arrivals, random services, and a single service channel) queuing delay model was also validated using the field delay data, and it was found that it estimates delay with high variability, especially for high delay ranges.

An increasingly popular method of managing freeway traffic is to use variable message signs (VMS). A neural network model is presented for real-time control of a VMS system in freeway work zones. The neural network is trained to detect the start of a queue in a work zone and provide a message in the freeway upstream. The travelers are informed about the congestion in a work zone when a queue starts to form. The intelligent VMS system can be trained with data for different periods within a day, such as morning and evening rush hours, nonrush hours during the day, and night, for a more detailed traffic flow prediction over the period of one day. Two different neural network training rules are used: the simple backpropagation (BP) and the Levenberg–Marquardt BP algorithms. The network is trained using data adapted from the measured data. Based on different numerical experiments it is observed that the convergence speed of the Levenberg–Marquardt BP algorithm is at least one order of magnitude faster than the simple BP algorithm for the work zone traffic queue detection problem.

A new mesoscopic-wavelet model is presented for simulating freeway traffic flow patterns and extracting congestion characteristics. A traffic speed–density relationship is introduced with a lane drop factor to take into account lane closures in freeway work zones. Patterns of multiple parameters are inputted to a congestion feature extraction algorithm. An approximate solution for this equation is found by space-time discretization. The high frequency fluctuations of the signal are not recognizable at normal resolutions. To overcome this problem, a multi-resolution wavelet filter is introduced in the proposed model to enhance traffic features and extract congestion characteristics from the traffic data. Fourth-order Coifman wavelets are used for filtering because of their good approximation for high-resolution scaling.

This research is based on the analysis of an origin-destination survey of users of Central Florida’s expressway system. It presents an initial investigation of the drivers’ choice in accessing/exiting the ramps of the system. The implications for route choice and spatial behavior are also addressed. The results showed that the distance traveled to access or after exiting a ramp does not depend only on the spacing between ramps, but on several factors, such as the trip purpose, vehicle occupancy, driver’s income level, and E-Pass use [whether the vehicle is equipped with an electronic toll collection system (ETC)]. A significant result also was that there is considerable difference in the drivers’ choices between entering and exiting the expressway. There is an indication that drivers prefer to access the expressway at shorter distances from their origins, but they are willing to travel longer distances to their destinations once they exit the expressway. A simplistic route choice analysis also presents some insights into the route choice paradigm. Route choice was found to be a function of several factors including the travel time, toll cost, and simplicity of the route (represented by the number of different roadway segments). The existence of a guide sign directing the driver to his/her destination also had an important impact on route choice, particularly for nonfamiliar travelers. Another factor, specific to toll roads, is the toll payment facility and toll payment method. Drivers of vehicles equipped with the ETC system (E-Pass), in a certain scenario, preferred a different route from drivers with no E-Pass. Finally, a multinomial logit route choice model was developed and illustrated the significance of several factors including the direction of travel, frequency of making the trip, age, residency, and E-Pass use on the likelihood of choosing a certain route. This research confirmed findings from previous work and the literature that route choice is a function of multiple factors and not only travel time or distance.

This paper presents a gray system theory-based method for the quantitative evaluation and ranking of the operational and safety performance of signalized intersections in urban areas under mixed traffic conditions. Mixed traffic conditions refer to traffic situations in which motor vehicles, bicycles, and pedestrians share a signalized intersection. Such mixed traffic is a typical phenomenon in many cities around the world in which the populations of urban areas are extremely large. Five index parameters are used in the proposed method: the degree of saturation, the average stopped delay, the queue length, the conflict ratio, and the separation ratio. These parameters represent the operational and safety performance of a signalized intersection with mixed traffic. They are inputted into the evaluation equations, which are developed according to the gray system theory. The method is applied to the performance evaluation of the intersections and network in the urban area of Changsha, China. The results show that the method can be used to conduct a comprehensive performance evaluation and ranking of signalized intersections under the mixed traffic conditions that are associated with urban road network systems.

This study presents an approach to extract properties from spatiotemporal traffic speed contour maps using tools from the field of digital image analysis. The new measures are derived from second-order statistics and quantify properties such as smoothness, homogeneity, regularity, and randomness in traffic operations. Four measures were selected: angular second moment (ASM), contrast (CON), inverse difference moment, and entropy. Each measure was used to characterize speed contour maps derived from different traffic conditions. To avoid information redundancy, correlation was examined between first- and second-order measures, which resulted in disqualifying one of the four measures. The sensitivity of the new measures to variations in traffic conditions was also investigated using nearly 14,000 30 min speed contour maps generated from a section of 5.44 km of the freeway in five weekdays. It was found that the speed range of 32–48 km/h exhibited the highest randomness (entropy) and least smoothness (ASM). The lowest level of homogeneity (CON) was observed in the range of 48–80 km/h. The new measures were also used to evaluate the level of service.

Since the realization that the Superpave specification parameter $\left|G^{*}\right|/\sin \delta$ is not adequate in rating polymer-modified binders for high temperature performance grading of paving asphalts, researchers have been seeking ways to refine this parameter to make it more sensitive to pavement performance and also find other possible parameters that may better relate to rutting resistance. Most of these efforts have led to positive results in the right direction, but each has its own set of limitations that is preventing immediate implementation of the suggested ideas. From among the various suggestions, the one that has the highest merit for possible use is the refinement of the Superpave specification parameter, namely, the term $\left|G^{*}\right|/(1-(1/\tan \delta \sin \delta \left)\right)$ that evolved through a theoretical derivation based on fundamental concepts. This performance-based specification term was shown to be more sensitive to the variations in the phase angle δ than the original Superpave specification parameter and thus described the unrecovered strain in the binders more accurately. Though this refinement led to better discrimination between rutting resistance of various asphalts, not all asphalts with the same performance-grade based on the new parameter behaved identically in their rutting performance in laboratory mixture test evaluations. By model fitting the master curve formed from $\left|G^{*}\right|/(1-(1/\tan \delta \sin \delta \left)\right)$ versus frequency data at various temperatures for each binder, a rut-controlling term was extracted that correctly graded the binders in terms of the mixture performance. However, this approach is not appropriate for routine use as it requires large sets of data generation at various temperatures to form the master curve before determination of the model parameters for the rut-controlling term. The present work proposes an alternative method of using the term $\left|G^{*}\right|/(1-(1/\tan \delta \sin \delta \left)\right)$ such that it can be easily adopted as a high temperature performance grading specification for asphalts and evaluates its efficacy through actual field performance data.