bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Stopping Behavior at Urban Signalized Intersections
Authors: Kim Wonchul , Zhang Junyi , Fujiwara Akimasa , Jang Tae Youn , Namgung Moon
Published: January 2009

Traffic accidents at signalized intersections are influenced by many environmental factors, including site layout, traffic volume, and signal operation. However, most traffic accidents are attributable to driver behavior in response to the environment, because responses to the environment vary with drivers’ individual characteristics, as observed in the concept of a dilemma zone (DZ) at intersection approaches. For DZ protection, the installation of traffic signals closer to the stop line (i.e., before the intersection) has been proposed in South Korea. Although such proposals have been implemented experimentally, the actual effect of this measure on driver behavior has not yet been investigated. A discrete choice model is used to identify the factors that influence drivers’ crossing and stopping behaviors at signalized intersections, under the assumption that traffic safety is at risk if the influence of the signal location is ignored. Two analyses are presented to assess the impact of signal location on driver behavior at intersections. Violations of stop line crossing behavior and remaining time to stop line are examined, and two types of driver behavior models are presented that address the effects of signal location and other factors. The results consistently reveal that traffic signal location affects drivers’ stopping behavior, suggesting that traffic signal location can jeopardize road safety and therefore should be considered in intersection design.
Traffic Controller Performance during Time-of-Day Transition at Coordinated Actuated Signal Systems
Authors: Yun Ilsoo , Best Matthew , Park Byungkyu (Brian)
Published: January 2009

Modern traffic signal controllers supply various transition methods that attempt to mitigate disruptions to normal signal operations during changes in time-of-day (TOD) timing plans. Comprehensive performance evaluations of transition operations during changes in TOD timing plans using three real traffic controllers are presented: the McCain 170E, the Econolite 2070 ATC, and the ASC/3-2100. Evaluation results based on hardware-in-the-loop simulation at a test site with four coordinated-actuated signalized intersections in Virginia indicated that (a) transition operation performance varied because of differences in the transition methods of the different controllers, (b) the Minimax family of transition methods (i.e., Shortway in the 170E controller and Smooth in the 2070 ATC controller) generally outperformed others, (c) the faster start of the transition operation available in the ASC/3-2100 controller provided significant benefits over the 2070 ATC controller, and (d) the 170E controller outperformed both the 2070 ATC and the ASC/3-2100 controllers.
Evidence of Unacceptable Video Detector Performance for Dilemma Zone Protection
Authors: Middleton Dan , Park Eun Sug , Charara Hassan , Longmire Ryan
Published: January 2009

The use of video imaging vehicle detection systems (VIVDSs) in Texas has increased dramatically, primarily as a result of safety issues and costs. Nonintrusive detectors are almost always safer to install at intersections than inductive loops because of the greater separation between passing motorists and the field crews installing the detectors. Other factors that have contributed to increased VIVDS usage include the flexibility in adjusting detection zones (e.g., with lane reassignments), the ability to send an image of the traffic stream to a traffic operations center, and the lack of damage to the pavement structure (unlike inductive loops, which require a saw-cutting process that weakens the pavement). Despite these advantages, VIVDSs require additional research in some situations to ensure safe operations. The research objective is to determine how well the current video imaging systems deployed by the Texas Department of Transportation provide dilemma zone protection at high-speed signalized intersections. Preliminary findings from data collected at one of the three planned sites indicate that the detection discrepancies between VIVDSs and in-pavement sensors are significantly different. These discrepancies are not always critical to safety but would increase intersection delay.
Robust Synchronization of Actuated Signals on Arterials
Authors: Zhang Lihui , Yin Yafeng
Published: January 2009

A robust approach is presented to synchronize actuated signals on arterials, mainly to address the issue of uncertain (not fixed) starts and ends of green of the sync phases. The robust counterpart of the mixed-integer linear programming model (MILP) for bandwidth maximization is developed to minimize the expected regret with respect to a set of high-consequence scenarios. The robust counterpart, another MILP, can be solved in polynomial time. Macroscopic and microscopic simulations are conducted to corroborate the validity and robustness of the resulting coordination plans.
Commute Replacement and Commute Displacement
Authors: Lyons Glenn , Haddad Hebba
Published: January 2009

Working by telecommunication has been the subject of research attention in transportation studies for many years. Particular consideration has been given to occasional working from home (home working) by (full-time, paid) employees who represent a tangible removal of commute trips on days that people work from home. However, little recognition or attention has been given to the fact that home working not only may be undertaken for part of a week but also may be undertaken for parts of given days. This paper focuses particularly on part-day home working. It defines and uses the term “varied spatiotemporal (VST) working” to describe working days in which at least 30 min of continuous working takes place at home accompanied by work taking place at the workplace. Notably, such home working does not remove the commute trips but can temporally displace one or both of them. The research reported in this paper builds on preceding survey work that had established that the number of people who practice VST working and the number of VST days worked appear to be about double those for full-day home working (which has typically been the focus of research attention). The results presented in this paper are based on 25 in-depth interviews with individuals who practice VST working. The aim of the research was to examine more closely and to understand the nature of VST working and the motivations and constraints for its practice and to consider its potential contribution as a transportation demand management measure.
Changes in Travel Behavior of Commuters between 1970 and 2000
Authors: Froehlich Philipp
Published: January 2009

The paper describes research on estimating sequential discrete choice models for mode choice, destination choice, and interzonal trip generation of commuters from 1970 to 2000 in Switzerland. The research was based on detailed data sets that tracked the development of private and public transportation systems and the socioeconomic variables at the local municipality level. Major changes in mode choice were identified by use of the estimated parameters of travel cost, quantity-adjusted car ownership cost, and car ownership per licensed driver. The results of the interzonal trip generation showed that demand reacted with positive elasticity to accessibility and that the accessibility of a zone became less important for the generation of interzonal work trips over time.
Estimated Value of Savings in Travel Time in Switzerland
Authors: Hess Stephane , Erath Alex , Axhausen Kay W.
Published: January 2009

Reliable measures of the value of travel time savings (VTTS) are crucial inputs into policy planning in any regional or national context. However, the evidence from secondary or parallel VTTS studies often differs from that from official or national studies. This paper presents evidence from a study aimed at merging evidence from four separate studies of VTTS conducted in Switzerland. The analysis shows the potential of models estimated jointly on the basis of the combined data and produces stable results that should be more representative of those for the overall population.
Analysis of Travel Time in Multiple-Purpose Trips
Authors: Soo Joyce , Ettema Dick , Ottens Henk F. L.
Published: January 2009

This paper investigates the travel time attributed to each activity in a trip chain by developing a travel-time price for multiple-purpose trips. Travel-time price is a ratio of the associated travel time of an activity to the activity duration. The travel-time price developed here has three characteristics. First, it accounts for the influence of sociodemographics and urban form characteristics on travel time. Second, it represents the intra-activity trade-off of travel time between activity duration and its associated travel time for different activity types. Third, it represents the interactivity trade-off of travel time between different types of activities. By using the data from the AMADEUS activity-travel diary collected in the Netherlands in 2000, a regression analysis was carried out for multiple-purpose trips stemming from one base, and the results were compared with those of an analysis of single-purpose trips from one base. The focus was on weekday, nonwork, out-of-home activities performed by heads of households. This daily activity behavior is interpreted as an outcome of the long-term decisions made about work and housing locations. The results indicated that, although multiple-purpose trips are not as common, they are more efficient than single-purpose trips. Sociodemographics and spatial characteristics were not statistically significant for the travel-time price of maintenance activities but were mostly significant for discretionary activities. In addition, nonwork out-of-home travel time is largely influenced by the duration of discretionary activities, gender, working hours, and the spatial setting.
Route Choice under Uncertainty
Authors: Han Qi , Timmermans Harry J. P. , Dellaert Benedict G. C. , van Raaij Fred
Published: January 2009

The provision of travel information may serve as a means of changing the behavior of individual travelers in ways that are beneficial to the transportation system at large. On the basis of the argument that a better understanding of travel behavior in the presence of traffic information is required, this paper reports on the analysis of a computer experiment investigating the effects of recommendations with different underlying control objectives on route choice under uncertainty. The results indicate that when potential congestion is anticipated, travelers use the recommendations provided as an indicator of the choices of other travelers as they conjecture the rate of compliance to reduce the uncertainty when they make decisions.
Examination of Traveler Responses to Real-Time Information about Bus Arrivals using Panel Data
Authors: Zhang Feng , Shen Qing , Clifton Kelly J.
Published: January 2009

In recent years, a considerable amount of money has been spent on intelligent transportation system projects for public transportation, most notably, real-time transit information systems. To date, strikingly few studies that have empirically investigated the effects of deployment of such a system have been completed. This paper examines the effects of real-time transit information on travelers’ behavior and psychology. The 2006-2007 University of Maryland (College Park) campus transportation panel survey data were used to examine how travelers responded to the ShuttleTrac system, a newly implemented real-time bus arrival information system for the university's shuttle service. Two fixed-effects models and five random-effects-ordered probit models were estimated to sort out the causal relations between ShuttleTrac system information use and two behavioral and five psychological indicators, respectively. It was found that use of the real-time information significantly increased the riders’ feelings of security about riding the bus after dark and boosted their overall level of satisfaction. However, it was not found to significantly increase travelers’ shuttle trip frequency, at least in the short term, perhaps because of a lack of enough time for adjustment of travel behavior. These results suggest that although transit agencies and scholars should not be too optimistic about achieving an immediate ridership increase by providing real-time information to travelers, they can expect positive psychological responses from transit riders.
Exploring Travel Behavior of Elderly Women in Rural and Small Urban North Dakota
Authors: Hough Jill A. , Cao Xinyu , Handy Susan L.
Published: January 2009

Many studies focus on the mobility patterns of elderly people. However, few studies have explored the mobility of elderly women in rural and small urban areas. Compared with their peers in large urban areas, these women tend to face greater challenges because of limited services and mobility options. Using data from 1,021 respondents to a survey conducted in North Dakota, this study examines the determinants of the travel behavior of elderly women. In particular, a multilevel conceptual ecological model was applied to identify how individual-level social environment and physical environment factors influence their travel patterns. Ordered probit models were estimated for the frequencies of nine types of trips. It was found that individual factors (e.g., self-efficacy and physical limitations), social environment factors (e.g., clubs and family), and physical environment factors (e.g., rural versus small urban areas) significantly affect the mobility of elderly women in North Dakota. The implications of these results for policies that aim to enhance the mobility of elderly women in rural and small urban locations are discussed.
Value of Travel Time Savings under Random Taste Heterogeneity
Authors: Rubite Caesar P. , Muromachi Yasunori
Published: January 2009

The purpose of this study was to assess the value of travel time savings (VTTS) of urban travelers in the setting of a city in a developing country. It contributes to the few empirical studies on calculations of the benefits of transportation facility development and evaluation. In practice, VTTS can be taken as an average value for the population. However, the wider socioeconomic disparities among travelers in cities in developing countries might suggest significant taste variations. The standard logit formulation fails to account for such random tastes. To capture the heterogeneity among individuals and the correlations between alternatives, this study explores the aptness and flexibility of the mixed logit formulation with revealed-preference data. By specifying a random travel time coefficient, it compares the total travel time savings by using different statistical distributions. Depending on the assumed statistical distribution of the travel time coefficient, the study reveals that significant increases in total travel time savings are achieved by the use of random coefficients logit compared with those achieved by the use of standard logit. The results indicate that by accounting for random taste variations among individuals, total VTTS increases by a minimum of 28% and a maximum of more than 80% compared with the values obtained by the fixed coefficients approach.
Statistical Modeling in Pavement Management
Authors: Ahammed M. Alauddin , Tighe Susan L.
Published: January 2009

Statistical analysis is one of the key aspects of engineering studies by researchers and transportation agencies. It is common to use regression analysis to develop a relationship between a response and one or more regressor variables. However, in many instances correlations between different variables are suggested and used for the prediction of an event without proper evaluation or interpretation of the developed models. This procedure may lead to gross errors, particularly when many senior engineers are retiring and leaving behind successors with limited skills. The issue is further complicated because engineers receive limited exposure to statistics during their undergraduate program and consequently must learn on the job; this situation can result in some key aspects to statistical analysis being missed. For example, the coefficient of determination, which can be meaningless in many circumstances, is used by many people to evaluate the adequacy of a model. Points of intersection of two or more trend lines are sometimes taken as the optimum value of various criteria without considering practical or engineering aspects. This paper focuses on some important aspects of statistical analysis and shows through various pavement engineering and management models how a model and resulting conclusion can be misleading. Proper evaluation of the causal relationship among variables and interpretation of the model are important to support a model's usefulness as well as to draw meaningful conclusions from it. A simple and concise approach is presented to aid researchers and practitioners with regression modeling.
Sensitivity of Design Parameters on Optimal Pavement Maintenance Decisions at the Project Level
Authors: Priya R. , Srinivasan K. K. , Veeraragavan A.
Published: January 2009

Sensitivity analyses are important parts of both studying complex systems and measuring the variation in input parameters on the response. They are useful to decision makers for understanding the robustness of the optimal solution that they are to adapt to variations of the parameters of the problem. The sensitivity of the optimal solution of a project-level pavement management problem is analyzed, and the robustness of the optimal solution to the interventions and the timing, cost, and benefit are investigated. The input parameters, which affect the optimal maintenance solution, are identified as the structural and functional condition parameters (defined in terms of deflection and roughness, respectively, at the beginning of the analysis period), traffic volume, growth rate, and discount rate. The problem of computing the optimal treatment and timing for a given budget level is modeled as a mixed integer nonlinear optimization problem and solved by using a computationally efficient network-optimization technique. The benefits are evaluated by considering the pavement performance and are quantified as the area between the performance curve and the threshold values. The optimal budget required for pavements in different structural and functional conditions as well as traffic levels is presented. The effect of initial pavement condition on the optimal maintenance actions as well as their timings is studied. The result of the sensitivity analysis showed that the cumulative standard axle loads and traffic growth rate have a significant effect on the selection and timing of rehabilitation and preventive maintenance actions. The effect of the discount rate on the maintenance management decisions is also presented.
Comparative Analysis of Long-Term Field Performance of Recycled Asphalt in California Environmental Zones
Authors: Zaghloul Sameh , Holland T. Joseph
Published: January 2009

A study was performed to evaluate the long-term performance of different pavement materials in California. The performance of many special materials, including recycled asphalt pavement (RAP), was evaluated for actual field performance rather than laboratory-based performance. The sections considered in this study were selected to allow the environmental impact on the performance of a specific treatment to be addressed and comparative analysis between two or more treatments to be performed. This paper focuses on a comparative analysis performed on 47 RAP sections located in three California environmental zones: desert, mountain, and north coast. Comparisons were made between the performance of the RAP sections and those of other treatments located within a reasonable distance on the same route. In total, 131 sections covering seven different treatments were considered. The performance comparisons were made with respect to in situ structural capacity, distress condition, roughness condition, and consistency of construction. Deterioration models were developed and used to estimate the in situ structural capacity, distress condition, and roughness condition for all sections at the same age (5 years) to allow fair comparisons. The expected structural, distress, and roughness service lives were also estimated for all treatments on the basis of the field-observed conditions. The results of the analyses suggested that in all three environmental zones, long-term RAP performance is likely to be comparable to other treatments located within a reasonable distance on the same route.
Field and Laboratory Evaluation of a Reflective Crack Interlayer in New Jersey
Authors: Bennert Thomas , Maher Ali
Published: January 2009

A research effort consisting of both field and laboratory testing was undertaken to evaluate reflective crack relief interlayer (RCRI) mixes as a means of mitigating reflective cracking in composite pavements. Extensive field testing that included falling weight deflectometer (FWD) and weigh-in-motion (WIM) sensors was used to establish applied loads and the resultant movements in the pavement structure. The resultant field movements were used to establish testing parameters for the laboratory study. The purpose of the laboratory program was to evaluate the reflective cracking potential through bending and expansion-contraction-type movements of plant-produced asphalt mixes consisting of different aggregate gradations and asphalt binder types commonly used in New Jersey for portland cement concrete pavement overlays. Results indicate that the combination of FWD and WIM data can provide valuable information for establishing realistic parameters for laboratory validation of asphalt mixes. The laboratory study clearly illustrated the benefit of using RCRI mixes that consist of a fine aggregate gradation and polymer-modified asphalt binders to minimize reflective cracking potential. However, future efforts should include more fatigue-resistant mixes that would overlay the RCRI mixtures, as well as efforts to ensure better construction practices during their placement.
Observations, Modeling, and Mitigation Related to Reflective Cracking on Composite Pavements in New York City
Authors: Mallela Jagannath , Von Quintus Harold L. , Farina Jason
Published: January 2009

As part of a 7-year field study, experimental composite pavement sections incorporating several reflective crack control treatments were built and investigated in New York City (NYC). The primary objective of this study was to identify cost-effective materials and methods to minimize reflective cracks in NYC composite pavements. The as-constructed experiment included several reflective crack control strategies such as fabrics, membranes, composites, fiberglass laminates, and saw and seal crack control techniques. These strategies were repeated for 15- and 20-ft joint spacings in the base portland cement concrete (PCC) pavement. Control sections without any treatments were also built for each of the two PCC base joint spacings as baseline references. Evaluations in the form of 10 visual condition surveys, five falling weight deflectometer surveys, forensic coring, and materials testing were conducted over the life of the experiment. Performance was measured in terms of crack initiation, length, and severity as well as load transfer deterioration across the reflective cracks. The saw and seal crack control technique and short joint spacing, in that order, had the most effect on mitigating reflective cracking. The saw and seal technique offers a life extension of at least 18.5% and 34% for the 20- and 15-ft joint spacings, respectively, when compared with the NYC Department of Design and Construction (NYCDDC) standard reflective crack control measure–a nonwoven polypropylene fabric interlayer. On the basis of these findings, it is recommended that NYCDDC switch its standard reflective crack mitigation practice to saw and seal and abolish the practice of skewing transverse joints in the PCC base. A saw and seal specification was developed to help NYCDDC implement this recommendation. Additionally, the data from this research represent a unique body of work that can be used in mechanistic-empirical modeling of this important distress type.
Dynamic Network Loading Model with Explicit Traffic Wave Tracking
Authors: Durlin Thomas , Henn Vincent
Published: January 2009

A dynamic network loading (DNL) model is presented: it can be used both for dynamic traffic assignment (DTA) and for an accurate description of traffic. The proposed DNL model is composed of (a) the link model based on the Lighthill-Whitham-Richards macroscopic first-order model solved with the wave-tracking method, (b) a new intersection model that generalizes the Daganzo macroscopic merge model to complex intersections, and (c) a traffic signal model that represents the mean effects of stage alternation on traffic in terms of delays and of capacity restrictions. Both the wave-tracking method and the traffic signal model are applied in a network context for the first time. The model can be consistently solved with various precision scales: low-precision scales to quickly provide a good estimation of travel times on the network for DTA purposes, and high-precision scales for accurate descriptions of traffic with all the desired modeling details.
Incorporating within-Day Transitions in Simultaneous Offline Estimation of Dynamic Origin-Destination Flows without Assignment Matrices
Authors: Balakrishna Ramachandran , Koutsopoulos Haris N.
Published: January 2009

An offline methodology is presented: it simultaneously estimates dynamic origin-destination (O-D) matrices, without using assignment matrices that incorporate within-day transition equations. The proposed formulation and solution approach extends a calibration method recently developed that directly uses the output of any network loading model (such as a dynamic traffic assignment or simulation model) so that the complex relationships between O-D flows and model outputs are accurately captured (as opposed to the more common method of approximate linear relationships based on the assignment matrix). The study extends the original formulation by incorporating spatial and temporal relationships among various O-D flows (transition equations). These transition equations link O-D flow variables across time intervals in such a way that known structural demand patterns can be preserved in the new estimates. Such transition equations, although common in the context of real-time O-D flows, complicate the offline simultaneous estimation of O-D flows and have not been used to their full potential in the past. The approach is demonstrated through a case study.
Effectiveness of Origin-Destination Matrix Correction Procedure Using Traffic Counts
Authors: Marzano Vittorio , Papola Andrea , Simonelli Fulvio
Published: January 2009

The estimation and correction of the origin-destination (O-D) matrix from traffic counts is a classical procedure usually adopted in transport engineering by practitioners to improve the overall reliability of transport models. Recently, Papola and Marzano showed through laboratory experiments that this procedure is generally not able to provide an effective correction of the O-D matrix. This result can be justified from a theoretical standpoint because of the lower number of stochastic equations (independent observed link flows) with respect to the unknowns (O-D flows). The current study confirms, first, that this circumstance represents the main reason for failure of the procedure by showing that good correction is generally obtained when the number of equations is greater than the number of unknowns. Then, since this circumstance does not occur in practice, in which the number of O-D pairs is usually much greater than the number of link counts, the study explores alternative assumptions and contexts that allow for a proper balance between unknowns and equations. In more detail, this balance can be achieved by moving to within-day dynamic contexts, in which a much larger number of equations is generally available. Obviously, to bound the corresponding increase in the number of unknowns, specific reasonable hypotheses in O-D flow variation across time slices must be introduced. In that respect, the effectiveness of the O-D matrix correction procedure in the usually adopted linear hypothesis on the dynamic process evolution of O-D flows and under the assumption of constant distribution shares is analyzed.
Enhanced Lagged Cell-Transmission Model for Dynamic Traffic Assignment
Authors: Szeto W. Y.
Published: January 2009

The lagged cell-transmission model (L-CTM) is an enhanced version of the CTM. Both can be incorporated into a dynamic traffic assignment framework for offline transport planning and policy evaluation and online intelligent transportation system applications. In contrast to the CTM, the L-CTM adopts a nonconcave flow-density relation, which can be used to predict the existence of rather dense traffic in queues coasting toward the end of the queue or to help disprove the existence of this phenomenon. However, this study shows that the L-CTM can yield unrealistic densities, namely, negative densities and densities higher than theoretical jam density, the former of which has not been addressed in the literature. To cope with these unrealistic results, this study improves the L-CTM by introducing one more term in each sending and receiving function of the model. The improved model, the enhanced L-CTM (EL-CTM), is proved to yield nonnegative densities not greater than the jam density but can still allow the use of nonconcave density relations. The EL-CTM yields Lighthill-Whitham-Richards solutions when cell lengths and time intervals tend to zero and includes the CTM and the L-CTM as special cases. The EL-CTM is also shown to give more accurate solutions than the L-CTM (and hence also the CTM) does under a small increase in computation time. Hence the EL-CTM is believed to be more suitable for both online and offline applications in the future.
Probit-Based Time-Dependent Stochastic User Equilibrium Traffic Assignment Model
Authors: Zhang Kuilin , Mahmassani Hani S. , Lu Chung-Cheng
Published: January 2009

This study presents a time-dependent stochastic user equilibrium (TDSUE) traffic assignment model within a probit-based path choice decision framework that explicitly takes into account temporal and spatial correlation (traveler interactions) in travel disutilities across a set of paths. The TDSUE problem, which aims to find time-dependent SUE path flows, is formulated as a fixed-point problem and solved by a simulation-based method of successive averages algorithm. A mesoscopic traffic simulator is employed to determine (experienced) time-dependent travel disutilities. A time-dependent shortest-path algorithm is applied to generate new paths and augment a grand path set. Two vehicle-based implementation techniques are proposed and compared in order to show their impact on solution quality and computational efficiency. One uses the classical Monte Carlo simulation approach to explicitly compute path choice probabilities, and the other determines probabilities by sampling vehicles’ path travel costs from an assumed perception error distribution (also using a Monte Carlo simulation process). Moreover, two types of variance-covariance error structures are discussed: one considers temporal and spatial path choice correlation (due to path overlapping) in terms of aggregated path travel times, and the other uses experienced (or empirical) path travel times from a sample of individual vehicle trajectories. A set of numerical experiments are conducted to investigate the convergence pattern of the solution algorithms and to examine the impact of temporal and spatial correlation on path choice behavior.
Stochastic User Equilibrium Model with Implicit Travel Time Budget Constraint
Authors: Smith Tony E. , Hsu Chao-Che , Hsu Yueh-Ling
Published: January 2009

Although time constraints on travel behavior have been widely recognized, little effort has been made to incorporate such constraints into the traditional stochastic user equilibrium (SUE) framework. The major objective of this research is to fill this gap by incorporating travel time constraints into the SUE model by means of a nonlinear perceived travel time function. This modified model, designated the travel time budget model, focuses primarily on discretionary travel behavior (such as shopping trips) and hence also allows the possibility of deferring travel decisions by incorporating an additional choice alternative designated the shop-less-frequently alternative. This model is compared with the traditional SUE model by using a simulated travel scenario on a test network designed to reflect a practical planning situation. The simulation shows that when attractiveness levels are increased by the introduction of a new shopping opportunity, the presence of travel time constraints can lead to significantly smaller predicted travel volumes than those of the traditional SUE model. More important, it shows that the overall pattern of travel can be quite different. In particular, travel to the shopping destination with enhanced attractiveness can actually decrease for some origin locations. The findings suggest that when an attempt is made to evaluate the impact of planning alternatives on future traffic patterns, it is vital to consider not only the cost of time itself but also the time trade-offs between travel and other human activities.
Lower-Bound Solution Algorithm for Equilibrium Signal-Setting Problem
Authors: Sadabadi Kaveh F. , Zokaei-Aashtiani Hedayat , Haghani Ali
Published: January 2009

The equilibrium signal-setting problem is stated and subsequently formulated as a continuous equilibrium network design problem. The bilevel formulation is nonconvex and therefore cannot be solved for global optima by using descent solution algorithms. Therefore, a lower bound using a system optimal flow pattern is proposed that will be quite tight in both uncongested and highly congested network traffic situations. A solution algorithm based on the standard steepest-descent method is proposed for the lower-bound problem. Performance of the solution algorithm on a network problem is reported.
Modeling User Responses to Pricing
Authors: Lu Chung-Cheng , Mahmassani Hani S.
Published: January 2009

In a previous contribution, the authors showed how to incorporate user heterogeneity in determining equilibrium route choices in a network in response to pricing. Presented here is a generalization of that framework to incorporate joint consideration of route and departure time as well as heterogeneity in a wider range of behavioral characteristics. A multicriterion simultaneous route and departure time user equilibrium (MSRDUE) model is presented, along with a simulation-based algorithm intended for practical network applications. The model explicitly considers heterogeneous users with different values of time (VOTs) and values of (early or late) schedule delay (VOESDs or VOLSDs) in their joint choice of departure times and paths characterized by a set of trip attributes that include travel time, out-of-pocket cost, and schedule delay cost. The problem is formulated as an infinite-dimensional variational inequality problem and solved by a column generation-based algorithmic framework that embeds (a) an extreme nondominated alternative-finding algorithm to obtain the VOT, VOESD, and VOLSD breakpoints that define multiple user classes and the associated least trip cost (joint departure time and path) alternative for each user class; (b) a traffic simulator to capture traffic flow dynamics and determine travel costs experienced; and (c) a path-swapping multiclass alternative flow-updating scheme to solve the restricted multiclass SRDUE problem defined by a subset of feasible alternatives. Application to an actual network illustrates the properties of the algorithm and underscores the importance of capturing user heterogeneity and temporal shifts in the appraisal of dynamic pricing schemes.
Calibration of Mechanistic-Empirical Models for Flexible Pavements Using California Heavy Vehicle Simulators
Authors: Ullidtz Per , Harvey John , Tsai Bor-Wen , Monismith Carl L.
Published: January 2009

Calibration of mechanistic-empirical models for pavement design is a very complex process. The heavy vehicle simulator (HVS) is ideal for the first step in this calibration process. The short test section can be carefully constructed with well-characterized materials and instrumented to measure the pavement response. The climatic conditions may be controlled or monitored closely, all load applications are known exactly, and perhaps most important, the pavement may be tested until it fails. This overcomes the problems of real pavements, which have uncertainties with regard to materials, loads, and climatic conditions and which are normally designed with a high reliability leading to very few failures. The mechanistic-empirical models of an incremental-recursive computer program, known as CalME, have been initially calibrated using data from 27 flexible pavement test sections tested with the two HVSs owned by the California Department of Transportation. Most sections were instrumented with multidepth deflectometers to compare the measured pavement deflections (at several depths) to the deflections predicted by the mechanistic model. Resilient deflections were compared for the complete time history of each test, and each test was carried to failure in regard to rutting (12.5 mm), cracking (2 m/m2), or both. This involved the calibration of models for changes in layer moduli, including the effects of asphalt fatigue. The comparison of measured and predicted response is essential to ensure that the pavement response is predicted reasonably well by the mechanistic model. Once this was achieved, models for permanent deformation of the individual pavement layers were calibrated against the measured permanent deformation of the layers, again using the complete time history of each test.
Adaptation of Mechanistic-Empirical Pavement Design Guide for Design of Minnesota Low-Volume Portland Cement Concrete Pavements
Authors: Khazanovich Lev , Yut Iliya , Husein Shariq , Turgeon Carly , Burnham Tom
Published: January 2009

A new Mechanistic-Empirical Pavement Design Guide (MEPDG) was recently proposed in the United States. The performance prediction models in the MEPDG were calibrated using nationwide pavement performance data. This study examined the feasibility of adapting a recent version of the MEPDG for the design of low-volume concrete pavements in Minnesota. To achieve this, a comprehensive evaluation of the MEPDG Version 0.910 performance prediction models was conducted. It was found that the faulting model produced acceptable predictions, whereas the cracking model had to be adjusted. Although performance data from the Minnesota Road Research facility were actively used in calibration of the MEPDG, it is necessary to perform calibrations against a wider range of local variables to achieve a practical design procedure for Minnesota. The cracking model was recalibrated using the design and performance data for 65 pavement sections located in Minnesota, Iowa, Wisconsin, and Illinois. A prototype catalog of recommended design features for low-volume portland cement concrete pavements in Minnesota was developed using MEPDG Version 0.910. The catalog offers a variety of feasible design alternatives for a given combination of site conditions. It is recognized, however, that Version 0.910 is not the final version of the MEPDG. Therefore, the catalog should be updated after the MEPDG software is finalized.
Detection of Delamination in Concrete Pavements Using Ground-Coupled Ground-Penetrating Radar Technique
Authors: Liu Juanyu , Zollinger Dan G. , Lytton Robert L.
Published: January 2009

The ground-penetrating radar (GPR) technique has been successfully used to identify some subsurface problems on highway projects. However, the technique (especially techniques that use ground-coupled GPR systems) has not been fully developed or widely applied to concrete pavement rehabilitation work because of the data quality and data interpretation associated with the use of GPR systems for such work, which are only fair. Hence, a study was undertaken to explore the feasibility and potential of using the ground-coupled GPR technique for the detection of shallow delamination in continuously reinforced concrete (CRC) pavements. This paper proposes a three-step analysis protocol for the detection of field delamination with improved quality and improved accuracy of data interpretation on the basis of field-collected GPR data and graphic output. The three steps of this protocol include (a) a preliminary evaluation, (b) the development of a site-calibration algorithm based on the GPR return waveforms, and (c) the establishment of a threshold amplitude difference. This approach was preliminarily evaluated through further testing in the field, and it was identified as a potentially promising and useful tool for assessment of the delamination of CRC pavements.
Effect of Traffic Load Measurement Bias on Pavement Life Prediction
Authors: Prozzi Jorge A. , Hong Feng , Leung Arthur
Published: January 2009

The new Mechanistic-Empirical Pavement Design Guide (MEPDG) requires comprehensive traffic inputs to predict pavement performance. Axle load spectra play a critical role in the impact of traffic on pavement performance. Weigh-in-motion (WIM) systems are becoming widely used as an efficient means of collecting traffic load data for mechanistic pavement design. The quality of the WIM-based data, however, remains a concern among pavement engineers. Previous research showed that WIM equipment calibration bias may lead to significant bias in the estimation of equivalent single-axle loads. This study investigated the effect of traffic load measurement bias due to WIM measurement errors on pavement life prediction on the basis of the mechanistic-empirical approach proposed by MEPDG. The results of this study not only support but also advance the existing research in this critical area. The findings of this study can be used to estimate pavement life prediction bias when inaccurate WIM data are used. They can also serve as guidelines for state highway agencies for the selection of WIM equipment and the establishment of criteria for equipment calibration.
Database Support for the New Mechanistic-Empirical Pavement Design Guide
Authors: Wang Kelvin C. P. , Li Qiang , Hall Kevin D. , Nguyen Vu , Gong Weiguo , Hou Zhiqiong
Published: January 2009

The proposed Mechanistic-Empirical Pavement Design Guide (MEPDG) developed under the NCHRP Project 1-37A initiative is a significant advancement in pavement design. However, it is substantially more complex than the 1993 AASHTO design guide and it requires significantly more input from the designer. Some of the required data either are not available or are stored in locations not familiar to designers. In addition, many data sets need to be preprocessed for use in MEPDG. Thus, there was a need to study the data requirements for MEPDG and produce a centralized database system to aid designers. This paper describes the development of a comprehensive database that can be used to store and process climate, traffic, material, and performance data for the state of Arkansas. The tasks undertaken were to (a) identify all the necessary input and analysis parameters required, (b) develop the database structures for uploading the required data, (c) locate the available data sets and begin populating the database, and (d) develop a data interface to the MEPDG software. The completed database will improve the management and accessibility of the MEPDG input data, and its completion is a critical step before the calibration and implementation of MEPDG.
Pavement Rutting Performance Prediction by Integrated Weibull Approach
Authors: Coleri Erdem , Tsai Bor-Wen , Monismith Carl L.
Published: January 2009

This paper demonstrates the applicability of the integrated Weibull approach to simulate the in situ rutting performance of asphalt concrete mixes by applying appropriate correction factors to laboratory models. The goal was to verify and calibrate the laboratory models according to accelerated pavement test results. The results of the repeated simple shear test at constant height (RSST-CH) were used to estimate the permanent deformation accumulation mechanisms. General regression equations were shown to successfully represent the Stage I and Stage II permanent deformation accumulation phases for mixes containing different binder types according to the results of RSST-CH. Correction factors were used to calibrate the laboratory equations according to the deflection data from four heavy vehicle simulator test sections to estimate in situ rutting performance. The results indicate that phase separation occurs at higher repetition values with increasing shear stress. Moreover, only Stage I of the laboratory models was actually valid at the high shear stress levels used for in situ rutting performance prediction. The simulations further confirm that the integrated Weibull approach is a successful and reliable method for prediction of the in situ rutting performance of flexible pavements and provides high coefficient of determination values.
Planning Approximations to the Average Length of Vehicle Routing Problems with Varying Customer Demands and Routing Constraints
Authors: Figliozzi Miguel Andres
Published: January 2009

This paper studies approximations to the average length of vehicle routing problems (VRPs). The approximations are valuable for strategic and planning analysis of transportation and logistics problems. The focus is on VRPs with varying numbers of customers, demands, and locations. This modeling environment can be used in transport and logistics models that deal with a distribution center serving an area with daily variations in demand. The routes are calculated daily on the basis of what freight is available. New approximations and experimental settings are introduced. Average distance traveled is estimated as a function of the number of customers served and the number of routes needed. Approximations are tested in instances with different customer spatial distributions, demand levels, numbers of customers, and time windows. Regression results indicate that the proposed approximations can reasonably predict the average length of VRPs in randomly generated problems and real urban networks.
Heuristic Framework for Optimizing Hurricane Evacuation Operations
Authors: Afshar Abbas Mohasel , Haghani Ali
Published: January 2009

In this research, an optimization framework is proposed to find the system-optimal solution for the emergency evacuation planning problem. The model simultaneously solves for the choice of destination (shelter), evacuation route, and departure time for all evacuees from given origins (endangered zones). Heuristic algorithms are proposed to find the system-optimal dynamic traffic assignment during an iterative procedure. A mesoscopic traffic simulator is embedded in the optimization modules to find travel time marginals and obtain required performance measures in every iteration. Implementing the proposed algorithm brings about dramatic improvements in network performance measures such as total travel time and network clearance time in a case study of Ocean City, Maryland.