bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Traffic Safety Benefits of Intelligent Transportation System Technologies at Truck Inspection Facilities: Microscopic Simulation
Authors: Saka Anthony A. , Glassco Richard A.
Published: April 2007

A microscopic simulation model was developed to capture the traffic safety benefits of using intelligent transportation system (ITS) technologies, including weigh-in-motion scales with variable message signs, at truck inspection facilities. The development of the simulation model was motivated by prevalent safety concerns at congested truck inspection facilities nationwide. Three primary safety components (roadway, driver, and vehicle) were considered in the model. The roadway component focuses on the varying size of truck queues at inspection facilities and safety implications. The driver component captures key human factor elements and their variability, including distributions for perception-reaction time, speed, gap acceptance, headway, and braking characteristics. The vehicular component incorporates the size distribution of vehicles (trucks and nontrucks), proportion of trucks with defective braking systems, and their safety implications with respect to stopping distance. The primary objective for the model is to depict variations in traffic pattern for baseline (pre-ITS) and post-ITS situations. Measures of effectiveness used for evaluating traffic benefits of using ITS technologies include percent reduction in sudden deceleration of vehicles resulting from shock wave phenomena and percent reduction in duration of truck-queue overflow resulting from a high traffic intensity. Results from simulation runs support the hypothesis that the use of ITS technologies at truck inspection facilities significantly reduces the frequency of experiencing the high-risk traffic phenomena (e.g., hard braking and truck-queue overflow). The postulation is made that the reduction in the frequency of high-risk phenomena will translate into a decrease in the likelihood of experiencing crash-related incidents in the vicinity of truck inspection facilities.
Finding Fault in Motorcycle Crashes in Hawaii: Environmental, Temporal, Spatial, and Human Factors
Authors: Kim Karl , Boski Joseph
Published: April 2007

Patterns of fault among drivers and motorcycle riders involved in collisions in Hawaii are examined. Personal and behavioral characteristics of drivers and riders involved in crashes are described, then temporal, roadway, and environmental factors associated with crashes between motorcycles and other motor vehicles are discussed. An argument is made that focusing on fault provides a strategic starting point for educational and traffic enforcement programs for drivers and motorcycle riders alike. A fault model is built by using logistic regression to predict the odds of fault for motorcyclists and vehicles involved in crashes. The spatial distribution of at-fault motorcyclists and drivers is mapped to determine if there are distinct spatial patterns for enforcement and educational efforts. The implications for motorcycle safety, driver education, law enforcement, and traffic safety research are discussed.
Analysis of Alcohol-Related Motorcycle Crashes in Florida and Recommended Countermeasures
Authors: Turner Patricia A. , Georggi Nevine
Published: April 2007

Although much progress has been made in reducing alcohol-related crash fatalities involving motor vehicles, the same success has not been demonstrated with motorcycles. Because the problem associated with drinking and riding is significant in Florida, the Center for Urban Transportation Research (CUTR) conducted a comprehensive analysis of motorcycle-alcohol crashes from 1993 to 1997 to understand how and why these crashes occur. CUTR also surveyed states about alcohol programs that target motorcyclists to gather information on potential countermeasures to reduce motorcycle-alcohol injuries and deaths in Florida. The study examined human-related and physical aspects of alcohol-related motorcycle crashes over the 5-year period to help establish an identity for this crash type. Examined human-related crash aspects included age and gender, alcohol use, licensing status, and helmet usage. Physical crash aspects examined included temporal patterns—time of day, day of week, and monthly trends—and contributing factors—first harmful event, road, environmental, and human factors—that cause bodily injuries or property damage. Major study recommendations include increasing efforts to get more motorcyclists properly licensed, greater exposure of messages to motorcyclists about the dangers of drinking and riding, and focused statewide public education and information campaigns. The study concludes with five major categories of countermeasures and recommendations to address the motorcycle-alcohol problem, including public information and education campaigns, promotional activities, enforcement efforts, community-based interventions, and data-collection needs.
Progress in Wheelchair Securement: Ten Years After the Americans with Disabilities Act
Authors: Hunter-Zaworski K. M. , Zaworski J. R.
Published: April 2007

Wheelchair securement is an issue in public transit that should have been resolved in the first few years after passage of the Americans with Disabilities Act (ADA). ADA requires that wheelchairs be secured so that they will not move more than 50 mm (2 in.) in any direction, even during a crash of the transporting vehicle. This requirement is of great interest to the existing securement industry and to wheelchair manufacturers. The former are interested because of the potential market for securement systems, and the latter because of the liability associated with use of their wheelchairs on public transit. In the 10 years since the ADA became law, some major advances have been made in securement technology. Unfortunately, current securement systems are essentially the same as those in use before ADA because work on standards for securement has been slow. Background on securement is presented, and work done on securement in the last decade is reviewed. The current status of wheelchair securement in public transit is discussed, particularly in the area of standards. Recommendations for speeding the acceptance of advanced securement technologies are made.
Information and Orientation Needs of Blind and Partially Sighted People in Public Transportation: BIOVAM Project
Authors: Marin-Lamellet Claude , Pachiaudi Georges , Le Breton-Gadegbeku Blandine
Published: April 2007

Presented are results of the BIOVAM project in France concerning the problems experienced by the visually impaired who use public transportation, such as buses, subways, and trains. The project focused on information gathering and orientation processes in the public transportation context. The BIOVAM approach uses a questionnaire survey to identify the main difficulties that public transportation users with visual impairment must manage. The approach includes a review of promising devices that could reduce these difficulties, such as personal information systems and tactile pavements. An overview of the results obtained from the survey is presented, addressing the use of buses and subways. The main technical solutions considered by the project are described, and the research protocols that are to be used in the field experiments are presented. The results of the BIOVAM project could be used to make concrete recommendations to include the specific needs of travelers with visual impairment in the design of a public transport infrastructure.
Impact of Urban Setting on Activity-Travel Patterns: Comparison of Performance Indicators with Quasi-Experimental Design Data
Authors: Snellen Danielle , Arentze Theo , Borgers Aloys , Timmermans Harry
Published: April 2007

The interest in activity-travel patterns has gained huge momentum lately. Most studies focus on analysis of particular aspects of such patterns and examine the relationships between aspects of activity patterns and sociodemographic variables. To complement this work, a study was conducted to examine whether and how activity-travel patterns vary across spatial settings. A set of descriptors was developed, and tests were conducted to determine whether these descriptors are significantly different across 8 cities and 17 neighborhoods. The results indicate that the organization of activity-travel patterns is relatively constant across urban settings. Characteristics of urban settings have a modest impact at best on descriptors of activity-travel patterns.
Implications of Urban Development for Travel Demand in the Netherlands
Authors: Maat Kees , Jaap Harts Jan
Published: April 2007

The assumption that travel demand is influenced by land use has long been applied in Dutch spatial planning policy. The aim of the present analysis is to explore how far this policy has succeeded in bringing about a compact and mixed spatial structure. Hence, a detailed analysis of the variation and development in the dispersal of urban activities, mix of uses, density, and diversity in urban areas between 1990 and 1996 is provided. It appears that although urban areas are leveling out on the one hand, they are undergoing a process of separation on the other. Although most of the building in the Randstad (the densely populated western part of the Netherlands) is taking place inside the designated urban regions, it is not producing compact monocentric towns; the urban areas are converging more and more, the metropolitan centers are losing their importance, and subcenters and concentrations of services are springing up on the edges of the urban regions. These phenomena confirm the emergence of complex, polycentric urban areas. Suburban sprawl is increasing rapidly in the intermediate zone outside the Randstad, where low-density residential areas, monoenvironments, and business estates are expanding. This region appears to have become the suburban search space for the Randstad. These dual trends will increase the distance between locations and make destinations less easily accessible by bicycle and public transport. Hence, neither the polycentric development inside the Randstad nor the suburban developments outside the Randstad will contribute to the reduction of car use.
Measuring Land Use Patterns for Transportation Research
Authors: Mitchell Hess Paul , Vernez Moudon Anne , Logsdon Miles G.
Published: April 2007

Density and land use mix are focused on as the two primary variables for characterization of land use in transportation research. As commonly constructed, these variables do not capture well actual development patterns on the ground, thus obscuring a potentially strong relationship between land use and transportation behavior. To overcome these limitations, parcel-level data and geographic information system software were used to identify and measure attributes of land use. These data are at a level of resolution that closely corresponds to the spatial distribution of development patterns. A method for location of concentrations of medium- to high-density housing and commercial development in suburban areas identified in previous research is described. The method includes the use of metrics derived from landscape ecology to model these development patterns and, specifically, their shapes and their functional and spatial
What Is the Effect of Commute Time on Employment?: Analysis of Spatial Patterns in New York Metropolitan Area
Authors: Macek Nathan M. , Khattak Asad J. , Quercia Roberto G.
Published: April 2007

Many planners argue that a key reason that residents of central-city and urban neighborhoods do not work is because of a lack of proximity to employment opportunities. The effect of travel time on employment probabilities for residents of urban areas was quantified while accounting for the fact that many are not employed. Data from the 1995 Nationwide Personal Transportation Survey ( n = 7,942 working-age individuals) were used to quantify the effect of commute time on employment for residents of the greater New York metropolitan area to test whether longer commute times are associated with lower employment probabilities. First, an ordinary least-squares regression model that explains travel times to work was estimated for those who work. This model was then used to predict the commute times by automobile and transit for all respondents in the New York–Northern New Jersey–Long Island consolidated metropolitan statistical area, regardless of employment status, on the basis of various personal characteristics including race and spatial attributes. Second, a binary probit model was used to estimate the employment probability on the basis of various personal and household characteristics as well as the predicted commute time. The results for work-eligible individuals showed that urban neighborhoods are characterized by a proportionately larger black population (25.1 percent of the urban population), with a relatively lower employment level (71.4 percent), longer average commutes despite the higher job density in urban areas, and relatively lower incomes. Central-city and urban residents reported travel times significantly different from those of their suburban counterparts. The commute times of urban and suburban residents with private vehicles were about equal and averaged 24 min, but urban transit commuters had an average commute of 40 min and suburban transit commuters had an average commute of about 60 min. Irrespective of race, the estimated employment probability for urban residents reliant on transit for commuting was substantially lower than that for urbanites who use automobiles. The findings support the need for policies to improve the accessibility and reliability of transit and to achieve a jobs-housing balance in central-city areas.
Assessment of Virginia Department of Transportation’s Use of Open-Forum Hearing Format
Authors: O’Leary Amy A. , Arnold E. D. , Kyte Cherie A. , Perfater Michael A.
Published: April 2007

Citizens have higher expectations for meaningful involvement in decision making than ever before. The Virginia Department of Transportation’s (VDOT’s) use of the open-forum hearing format was assessed in response to pending legislation requiring the use of the traditional format for all highway location hearings. VDOT staff were concerned that substantial public input might be lost if this occurred. A comprehensive review of the literature on hearing formats, a survey completed by 235 citizens, and a survey on hearing formats completed by 84 transportation professionals representing 43 states are included. Citizens’ preferences for the ways in which hearings are conducted—one-on-one interaction, flexible scheduling, and the opportunity to comment in private—supported VDOT’s continued use of the open forum. The open-forum format does not, however, typically provide two features that some citizens want: the formal presentation about the project and the opportunity to hear the comments that others (“neighbors”) make for the record. The open forum was also the format of choice among transportation professionals. It was rated more highly (often substantially more highly) than either the combined format or the traditional format on seven of eight dimensions included in the survey. The exception was “providing what interest groups seem to want.” A compromise bill was engineered in the 2000 legislative session of Virginia’s General Assembly that would require VDOT to incorporate a public comment component into a location hearing upon the request of the local governing body or 25 or more citizens.
Measuring Customers’ Views of Transportation Planning Services: A Reusable Survey
Authors: Miller John S.
Published: April 2007

Customers of the Virginia Department of Transportation (VDOT) who use its transportation planning services include towns, cities, counties, planning district commissions (PDCs), metropolitan planning organizations (MPOs), and advocacy groups. To assess VDOT’s delivery of these services and identify areas for potential improvement, approximately 300 questionnaires were distributed to customers statewide. The questionnaire categorized planning functions into seven services (performing strategic long-range planning, providing liaison services, conducting passenger planning, conducting freight planning, performing site plan reviews, assisting with modeling and quantitative analysis, and answering questions and providing technical assistance) and asked recipients to identify the providers, evaluate service delivery, and rank the services in order of importance. Customers were most interested in strategic long-range planning. Localities were most interested in site plan reviews, and MPOs, PDCs, and VDOT’s urban districts were most interested in modeling and quantitative analysis. Urban respondents ranked modeling and quantitative analysis as the service that VDOT performs best, whereas rural respondents gave answering questions and providing technical assistance this ranking. The survey cannot replace in-depth discussions between a provider of transportation planning services and its customers, but it can yield practical customer input stratified across the seven services described.
St. Louis Redefines Community Engagement
Authors: Smith Hansen Janeen , Jackson Margaret Campbell
Published: April 2007

Although community engagement has become a generally accepted and often required part of major public project planning, a study recently completed in St. Louis, Missouri, demonstrates the importance of project sponsor and technical team commitment to the process. The East-West Gateway Coordinating Council (EWGCC), the metropolitan planning organization in St. Louis, conducted a comprehensive community engagement process in three study areas aimed at “fully engaging the community at the earliest stages of planning.” Furthermore, EWGCC created a three-agency umbrella organization to sponsor the studies, with the organization facilitating interagency cooperation from the inception of the work. By negotiating independent contracts with the community engagement and technical teams, the project sponsor ensured that community engagement would direct and guide the technical work rather than respond to technical analysis after the fact. In a unique partnership of public agencies, community engagement specialists, and technical experts, the St. Louis study illustrates the essential ingredients for a successful community engagement process. First, there was commitment from the top of each organization. Second, the project sponsors place “customers” first in analyzing the region’s transportation needs. Third, the technical team was wholly committed to the community engagement process, working hand in hand with the community engagement team. Finally, building and maintaining a successful team was an ongoing, multistep process in which all parties participated from the beginning to the end of the study.
Contractor-Led Public Relations on a Design-Build Highway Project
Authors: Ernzen Jim , Woods Janet
Published: April 2007

Recent innovations by the Arizona Department of Transportation (ADOT) in the area of public relations for highway construction are presented. Explosive population growth in Arizona has pushed ADOT to the limits of its capacity and has challenged ADOT to develop innovative ways to stretch its resources to meet constituents’ needs. In 1996 the state legislature passed legislation enacting a pilot design-build program aimed at completing public construction projects more rapidly than could be done by traditional methods. The second project in the program—which involved widening from 6 to 10 lanes 13 km (8 mi) of Interstate 17, a primary artery carrying 180,000 vehicles per day through the city of Phoenix—is described. ADOT established public relations requirements for the design-build contractor, evaluated each proposer’s response to those requirements, and then worked with the winning design-build team to administer the public relations program for the project. An important requirement of the program was the use of public opinion surveys performed by the design-builder throughout the project to measure the effectiveness of the public relations program. The survey results provided the basis for a unique financial incentive program used on the project. The results of the public opinion surveys and corresponding incentive payments are presented.
Development of High-Occupancy Vehicle Facilities: Review of National Trends
Authors: Fuhs Chuck , Obenberger Jon
Published: April 2007

High-occupancy vehicle (HOV) lanes have existed for more than 30 years. As a congestion management strategy, HOV lanes have been widely applied in the United States to preserve mobility, maintain trip reliability, and improve the person-moving capability within a corridor or metropolitan area. Although there are many examples of successful HOV lanes that carry large numbers of commuters and buses, criticism has been levied toward HOV lanes in some metropolitan areas. A lack of information and data about the benefits of HOV lanes, the nationwide trend toward less carpool use, and the closure of two projects in New Jersey in 1998 have resulted in reassessment of the purpose, role, and benefits of HOV lanes by some metropolitan areas and agencies. This has led some to postulate that the HOV lane concept may no longer be viable. In response to these perceptions, available data are reviewed and some perspectives are provided on the recent past and possible future of HOV lanes, particularly the treatments applied on urban freeways that represent the majority of such applications. A summary of recent experiences, growth, type, and changes that have occurred with HOV lane operational policies is presented. Many of these trends have been influenced by federal legislation over the last 15 years, specifically the Clean Air Act and operational policies related to the development of HOV lanes as a congestion management strategy. Trends in future HOV lane development, based on the current roadway improvement plans of various states, are presented to provide a prospective for future policy and programming considerations.
PAMELA: Parking Analysis Model for Predicting Effects in Local Areas
Authors: van der Waerden Peter , Timmermans Harry , Borgers Aloys
Published: April 2007

The development of a parking simulation model is reported. The conceptual framework underlying the simulation model is described in detail. Empirical results of completed modules of the parking simulation model are presented. Future research directions are discussed.
Tracking the Duration of New Commute Modes Following Service from a Ridesharing Agency: Longitudinal Study
Authors: Smith Virginia , Beroldo Steve
Published: April 2007

Monitoring the effectiveness of a ridematching service requires the analysis of two factors: the percentage of people who successfully change commute mode as a result of the service and the amount of time that people continue to use the new mode. The second factor is addressed by identifying a group of commuters who made a change in commute mode after receiving service from a ridesharing agency (RIDES for Bay Area Commuters, Inc.). This group of commuters was contacted quarterly over a period of 6 years and asked how they were getting to work. The average amount of time a client used the new mode was between 1.6 years and 1.9 years. The data show that somewhere between 8% and 14% of all clients will continue to use the new commute mode until they are no longer making the trip to work. Of all possible commute modes, people who travel in vanpools are the most likely to continue with their new mode for the longest period (more than 3 years).
Development of a Congestion Management System Methodology for the Indiana State Highway Network
Authors: Choocharukul Kasem , Sinha Kumares C. , Nagle John L.
Published: April 2007

A methodology for developing congestion management–related projects for the Indiana state highway network is described. The methodology is based on a sketch planning analysis technique that can be used with limited input data. The software package provides estimates of costs and other effects of potential congestion mitigation projects to undertake in a given year, which can be used by planners and programmers in long-range planning. Project types include road widening, high-occupancy-vehicle facilities, ramp metering, incident management, and arterial traffic signal coordination. The impact is assessed in travel time savings, vehicle operating cost savings, crash cost savings, and emission reductions. An example application of the methodology is given for the 7.81-mi segment of I-65 between Interchanges 116 and 123 in the Indianapolis area.
Public Preferences for Managing the Upper Mississippi River System
Authors: Carlson Bruce D.
Published: April 2007

The human dimension is an important, yet often overlooked, aspect of river ecosystem analyses. To provide decision makers with information to maintain the Upper Mississippi River System (UMRS) as a viable large river system, a survey of the general public was designed and conducted in 1996 to assay river resource values and expectations. Members of 500 randomly selected households in each of the five UMRS states completed the survey (total of 2,500). Factor analysis, reliability analysis, and analysis of variance techniques were employed in the data analysis. Results show that citizens value the river strongly for multiple purposes and expect balanced use in its management. An important point is that although there is not a consensus regarding future management of the UMRS, levels of support do not vary substantially across regions. Differences in preferences between the general population and more active stakeholders suggest that strategies for engaging the public be reconsidered.
Expansion of the Port of Rotterdam: Framework for Evaluation
Authors: Dekker S. , Verhaeghe R.J. , Pols A.A.J.
Published: April 2007

Ports require large investments from public and private sources. Although they generate benefits to the regional and national economy, they have important negative effects on the environment and cause traffic congestion as well. Competition between ports has increased substantially. As a result, port efficiency and commercial attractiveness have received more emphasis. The traditional role of government in providing port infrastructure is increasingly being questioned. Public and private roles need to be differentiated more clearly. These factors cause a rising interest in untangling issues of public welfare and commercial interests; a proper framework for evaluation is called for. In response, a framework for evaluation by differentiating public welfare and commercial aspects is presented. The framework is applied to a planned project for seaward expansion of the Dutch port of Rotterdam: project Maasvlakte 2. In this framework, it is necessary to ( a) adopt a proper economic scenario and associated demand forecasts for port services, ( b) account for alternatives to the physical expansion of the port area, and ( c) account for the indirect and external effects of port activities. In particular, the indirect effects play a crucial role in the evaluation of a project such as Maasvlakte 2, as they are expected to represent a major portion of the net contribution to public welfare.
Containerport Investment Appraisal and Risk Analysis: Illustrative Case Study
Authors: Grigalunas Thomas A. , Chang Young-Tae , Luo Meifeng
Published: April 2007

There are considerable economic and political pressures to expand existing and develop new containerports to accommodate the increasing trade of containerized cargoes carried on ever-larger vessels. However, port development involves a major investment and poses many financial, economic, and environmental risks. The major sources of financial risk facing prospective terminal operators are reviewed and methods to identify the overall financial risk and importance of individual sources of risk are illustrated. Methods used focus on net present value and the use of extensive sensitivity analyses as well as the use of the more formal Monte Carlo analysis. A dynamic discrete-event model is also employed to assess the internal consistency and feasibility of a developer’s port plans and projected operations. Generalized data from previous early engineering-economic studies of a proposed port at Quonset Point, on Narragansett Bay, Rhode Island, are employed to illustrate the use of these methods. Four specific risks are considered: start-up volume of moves, growth rate of moves, costs, and efficiency of yard operations. Results suggest that the start-up volume and growth rate of moves are critical factors in the financial success of a proposed port. Results can be extended to more variables and refined when information on more current specific port plans becomes available.
Petri Net Modeling and Analysis of Automated Container Terminal Using Automated Guided Vehicle Systems
Authors: Liu Chin-I. , Ioannou P. A.
Published: April 2007

Booming world trade, scarcity of land for yard expansion in many ports, and deployment of new, massive megaships have magnified the need to find better ways of performing container terminal operations. Automated guided vehicle systems (AGVS) have been proposed as possible candidates for future automated container operation because of their ability to significantly improve the performance of container terminals. However, before the deployment of AGVS, computer model simulations to investigate the potential problems are necessary to successfully implement the system. Petri net is a well-known modeling tool that, with the advantages of its graphic nature and the availability of mathematical analysis techniques, is clearly suitable for the application of automated container terminal systems (ACTS) modeling. A timed-place petri net (TPPN) model of ACTS using automated guided vehicles (AGVs) is constructed. The TPPN model contains a transportation layout module, two unit submodels, an AGV unit submodel, and a crane unit submodel. The transportation layout module serves as a basic unit to construct the transportation road map of the system. The AGV unit submodel is used to model the traveling behavior of the AGV on a node-to-node basis, and the crane unit submodel is used to model the crane’s container-loading and -unloading movement. A collision-free control rule, which is primely modeled using inhibitor and actuator arcs, is embedded in the submodels to ensure a collision-free environment for the AGVs. The important properties of the model such as liveness, safeness, and reversibility are analyzed.
Optimal Improvement Scheme for Network Reliability
Authors: Yin Yafeng , Ieda Hitoshi
Published: April 2007

Performance reliability of road networks has become a more prevailing concern for engineers and planners involved in network design. To improve network reliability the most, engineers and planners may need to decide which links need improvement and at the same time account for the route choice behavior of network users. Using a simple network example, a new reliability version of Braess’s paradox is presented showing that increasing the capacity or decreasing the variability of travel time for some links may actually lead to a less reliable network. A bilevel programming model is proposed through which the reliability paradox can be avoided and an optimal improvement scheme for the existing links may be determined to achieve the most reliable network, subject to a budget constraint. Finally, a numerical example is presented to illustrate the model together with a sensitivity analysis–based algorithm.
Travel Time Minimization Versus Reserve Capacity Maximization in the Network Design Problem
Authors: Yang Hai , Wang Judith Y. T.
Published: April 2007

In the classical continuous network design problem, the most common approach is to determine optimal capacity enhancement by minimizing the total system cost under a budget constraint while taking into account the route choice behavior of network users. An alternative objective, maximization of network reserve capacity, is examined with the expectation that it is equivalent to total system cost minimization to a certain extent. The two approaches are tested and the results are compared in order to assess the level of equivalence and their effectiveness. The level of equivalence of the two objectives is found to vary by level of congestion. When the level of congestion is low, maximization of network reserve capacity is found to have the simultaneous effect of total cost minimization. This objective becomes more desirable when the level of congestion is low. When the level of congestion is high, maximizing the reserve capacity can only minimize the total travel cost to a certain extent. In this case, a combined objective can also be considered by applying different weightings on the two objectives.
Travel Time Reliability with Risk-Sensitive Travelers
Authors: Chen Anthony , Ji Zhaowang , Recker Will
Published: April 2007

In recent empirical studies on values of time and reliability, many have suggested that travelers are interested not only in travel time saving but also in reduction in travel time variability. Variability introduces uncertainty for travelers such that they do not know exactly when they will arrive at their destination. Thus, it is considered as a risk (or an added cost) to a traveler making a trip. Continuing research is reported on route choice models and the effect on travel time reliability in an uncertain environment caused by demand and supply variations. The goal is to examine what the aggregate impact of changes in variability might be on network assignment and how travelers with different risk-taking behaviors respond to these changes.
Adaptive Speed Estimation Using Transfer Function Models for Real-Time Dynamic Traffic Assignment Operation
Authors: Huynh Nhan , Mahmassani Hani S. , Tavana Hossein
Published: April 2007

The application of a transfer function model (TFM) in a real-time dynamic traffic assignment system is investigated. The motivation is to improve the speed estimation method to enable better system consistency with reality in real-time operation. The study is conducted by adopting a TFM derived from actual detector data in San Antonio, Texas. This model is then used in the traffic simulation module of the DYNASMART-X dynamic traffic assignment system to update the network link speeds. A nonlinear least-squares optimization algorithm, implemented for this study, is coupled with DYNASMART-X to enable adaptive estimation of the TFM parameters. Simulation-based experiments are carried out on the Fort Worth test network. These experiments are designed to evaluate the TFM performance and to gain insight into its operational properties under different conditions. The results show that the TFM, both adaptive and nonadaptive, can consistently approximate the true underlying speed-density dynamics. Of significant importance is the transfer-ability and robustness of TFMs in different settings. The outcome of this research substantiates the premise that good speed estimation can be achieved through the use of TFMs.
Hybrid Real-Time Dynamic Traffic Assignment Approach for Robust Network Performance
Authors: Chiu Yi-Chang , Mahmassani Hani S.
Published: April 2007

A hybrid dynamic traffic assignment (HDTA) approach is presented that results in robust performance of the traffic network under various scenarios. The HDTA approach envisions a hierarchical routing decision process achieved through the careful interplay between a centralized DTA (CDTA) model and a decentralized DTA (DDTA) capability. The CDTA model supplies anticipatory a priori routing decisions, whereas the DDTA model generates locally optimized solutions online. Analytical and experimental analyses are conducted to illustrate the satisfactory performance of such an HDTA approach.
Combined Model for Time-Dependent Trip Distribution and Traffic Assignment
Authors: Li Yue , Ziliaskopoulos Thanasis , Boyce David
Published: April 2007

A combined model for time-dependent trip distribution and traffic assignment is proposed. The model assumes known time-dependent departure rates from origins and overall arrival rates at destinations, and it then seeks to estimate the origin-destination matrix according to the observed entropy value and to minimize the total system travel time. A solution algorithm is proposed based on the Dantzig-Wolfe decomposition principle and a Lagrangian relaxation approach. Computational results on a test network are also presented and discussed.
Snow Emergency Vehicle Routing with Route Continuity Constraints
Authors: Haghani Ali , Qiao Haiying
Published: April 2007

New results are presented from continuing research dealing with development of a decision support system to assist the Maryland State Highway Administration Office of Maintenance staff in designing snow emergency routes for Calvert County, Maryland. By taking into account some of the more realistic constraints, an attempt is made to solve two problems. One involves minimizing the total number of trucks, and the second one involves minimizing the total deadhead distance given the number of trucks. The two problems do not result in identical solutions in general. The first problem is formulated as the well-known capacitated minimum spanning tree (CMST) problem. The second problem is also formulated as a CMST problem but with an approximate function for total deadhead distance. Some application results are also reported, which indicate that using such a system can achieve improvements in service and savings in operational costs.
Dynamic Procedure for Short-Term Prediction of Traffic Conditions
Authors: Lin Wei-Hua , Lu Qingying , Dahlgren Joy
Published: April 2007

Many existing models for forecasting traffic conditions are based on traffic flows. Field data are used here to show that these traffic conditions may not fluctuate from day to day in the same manner as does the traffic flow. Consequently, flow data are inappropriate for predicting traffic conditions because the same flow level may correspond to either a congested or a free-flow traffic state, a phenomenon that can be easily explained with the flow–density relationship. Occupancy, which is proportional to density, is a better indicator of traffic condition. A simple dynamic model based on occupancy data is proposed. The model utilizes occupancy and occupancy increments in an integrated way and treats them as two random variables represented by two normal distribution functions. It is shown that flow data, which are more stable than occupancy data, can be used indirectly to improve the performance of the proposed model. Self- and cross-validation efforts are made to examine the performance of the model. The results are promising. The expected absolute deviance for predicted occupancy (ranging from 0 to 100%) is about 1.25%, which is accurate enough for most applications. The model requires little effort in calibration and computation and is exceedingly simple to implement in the field.
Design and Operational Concepts of High-Coverage Point-to-Point Transit System
Authors: Cortés Cristián E. , Jayakrishnan R.
Published: April 2007

Conceptual design and preliminary feasibility simulation results are presented for a flexible transit system for travel from any point to any point based on real-time personalized travel desires, which is now possible because of advances in communications and computing technologies. Although it is demand-responsive, the concept is significantly different from older demand-responsive transit systems, which were often failures. The proposed system requires high coverage, referring to the availability of a large number of transit vehicles (often minibuses or vans), which could also operate in conjunction with private transit and paratransit systems. The design strictly eliminates more than one transfer for any passenger. The system could potentially provide a transit alternative that is much more competitive with personal automobile travel than are conventional transit systems because of significantly lower waiting times. The passenger demand for such a system is uncertain, but preliminary simulations show that under a variety of acceptable demand levels, the system can operate with high cost-effectiveness. The focus is on describing the details of the concept and providing arguments in favor of the system based on simulations. The system essentially attempts to solve a stochastic real-time passenger pickup-and-delivery problem with a large number of vehicles. A strict optimization formulation and solution for such a problem are computationally prohibitive in real time. The design proposed is effectively geared toward a decomposed solution using detailed rules that achieve vehicle selection and route planning. If real-time update of probabilities is included, this scheme could be considered as a form of quasi-optimal stochastic control.
Feasibility of Driver Judgment as Basis for a Crash Avoidance Database
Authors: Smith David L. , Najm Wassim G. , Glassco Richard A.
Published: April 2007

A crash avoidance database structure that is based on driver judgments is proposed. The structure comprises four driving conflict states (low risk, conflict, near crash, and crash) that correspond with advisory warning, crash-imminent warning, and crash mitigation counter-measures. The feasibility of this database structure is investigated by answering two questions: ( a) Can the driving states be reliably quantified? and ( b) Can the quantified states be used to create a useful crash avoidance database? The feasibility discussion centers on a specific dynamic scenario that involved braking maneuvers by a following vehicle to avoid a rear-end crash with a stopped lead vehicle. The quantification of driver judgment data from a controlled test track study is discussed as a foundation to identify rough quantitative locations for the conflict and near-crash state transitions, and crash data from a driving simulator experiment are used to estimate the crash state boundary. A database of on-road, naturalistic driving data is compared with the controlled experiments to evaluate the results. The method is found to be feasible, and recommendations for further development are presented.
Application of Accident Prediction Models for Computation of Accident Risk on Transportation Networks
Authors: Lord Dominique
Published: April 2007

Accident risk has been applied extensively in transportation safety analysis. Risk is often used to describe the level of safety in transportation systems by incorporating a measure of exposure, such as traffic flow or kilometers driven. The most commonly applied definition of accident risk states that risk is a linear function of accidents and traffic flow. This definition, however, creates problems for transportation systems that are characterized by a nonlinear relationship between these variables. The primary objective of the original research was to illustrate the application of accident prediction models (APMs) to estimate accident risk on transportation networks. (APMs are useful tools for establishing the proper relationship between accidents and traffic flow.) The secondary objective was to describe important issues and limitations surrounding the application of APMs for this purpose. To accomplish these objectives, APMs were applied to a computerized transportation network with the help of EMME/2. The accident risk was computed with the traffic flow output of the computer program. The results were dramatic and unexpected: in essence, the individual risk of being involved in a collision decreases as traffic flow increases. The current and most common model form of APMs explains this outcome. The application of these results may have significant effects on transportation policy and intelligent transportation system strategies.
Screening the Road Network for Sites with Promise
Authors: Hauer Ezra , Kononov Jake , Allery Bryan , Griffith Michael S.
Published: April 2007

Network screening is the first step in the site safety improvement process. The product of network screening is a list of sites that are ranked by priority for the conduct of detailed engineering studies. In turn, cost-effective projects are formulated from the studies. With the purpose of laying the foundation for improved network screening, the role of network screening is clarified, and how project cost and safety benefit can be anticipated at the time of screening is examined. The strengths and weaknesses of alternative assumptions on which the anticipation of safety benefit can be based are discussed. A way to guard against misallocation of resources due to the randomness of accident counts is suggested, and a method for finding peak sites within road sections is proposed.
Development of a Road Safety Risk Index
Authors: Leur Paul de , Sayed Tarek
Published: April 2007

The cornerstone of most safety management programs consists of a “collision-prone location” program, where significant collision history must exist and be identified before improvements are recommended. Often, these programs are solely dependent on collision records and thus program success is governed by the data quality. Unfortunately, in many jurisdictions in North America, the quantity and quality of collision data have been degrading for several years. This growing problem is jeopardizing the success and continuance of many road safety programs. To help mitigate this problem, it is believed that a subjective evaluation technique could be developed that does not rely on collision statistics and that could be used to identify and diagnose problematic areas. The development and application of a risk index used for road safety evaluation are described. The risk index is developed as a driver-based, subjective assessment of the potential road safety risks for in-service roadways. The objective of developing the safety risk index is to produce a technique to support road safety analysis that does not rely on deteriorating collision data. The road safety risk index was developed and tested to ensure consistency between observers in their subjective assessment of safety. In addition, the results from the risk index were compared with results from objectively derived road safety measures to evaluate the success of the road safety risk index. The comparison indicates that there is a statistically significant agreement between the results of the risk index and the objectively derived road safety measures.
Calibration and Transferability of Accident Prediction Models for Urban Intersections
Authors: Persaud Bhagwant , Lord Dominique , Palmisano Joseph
Published: April 2007

Accident prediction models, also known as safety performance functions, have several important uses in modern-day safety analysis. Unfortunately, calibration of these models is not straightforward. A research effort was undertaken that demonstrates the complexity of calibrating these models for urban intersections. These complexities relate to the specification of the functional form, the accommodation of the peculiarities of accident data, and the transferability of models to other jurisdictions. Toronto data were used to estimate models for three- and four-legged signalized and unsignalized intersections. Then the performance of these models was compared with that of models for Vancouver and California that were recalibrated for Toronto using a procedure recently proposed for the application in the Interactive Highway Safety Design Model (IHSDM). The results of this transferability test are mixed, suggesting that a single calibration factor as is currently specified in the IHSDM procedure may be inappropriate and that a disaggregation by traffic volume might be preferable.