bluuebunny/crossref_metadata_2025 huggingface dataset:
Freeway Systems Research Beyond Highway Capacity Manual 2000
Authors: May Adolf D. , Rouphail Nagui , Bloomberg Loren , Hall Fred , Urbanik Tom
Published: April 2007

The Highway Capacity Manual 2000 (HCM 2000) contains new procedures for the analysis of directional freeway facilities that were developed and assessed during the past 3 years by a research team. This experience in developing the freeway facility chapter and, later, in assessing these procedures has led to the identification of freeway research needs beyond HCM 2000. The findings of the assessment process for HCM 2000 procedures and other traffic models are highlighted, and recommendations for future research are provided. Areas of investigation and identified research needs include free-flow speed estimation, upper-limb speed-flow relationships, capacity estimation, lower-limb speed-flow relationships, characterization of the oversaturated regime for freeway facilities, and other traffic models.
Highway Capacity Analysis After Highway Capacity Manual 2000
Authors: Kittelson Wayne K. , Roess Roger P.
Published: April 2007

The publication of the “fourth” full edition of the Highway Capacity Manual (HCM) in the fall of 2000 represented a major step forward in state-of-the-art highway capacity and quality-of-service analyses. Even as this major step is taken, however, old issues reemerge and new ones arise as to the core concepts involved, the directions that such analyses should take in the future, and the needs of HCM users. Now that HCM has begun to address system and multimodal measures, the nature and meaning of capacity and level-of-service concepts need to be reexamined. The role of simulation must be more clearly defined, as must the limitations of more conventional highway capacity analyses. As databases improve, the question of statistical accuracy and stochastic variations in standard measures may seem more important, even though the inherent variability in traffic flow characteristics remains essentially unchanged. The need for software to implement ever more complex methodologies raises additional issues. As the Committee on Highway Capacity and Quality of Service and its members consider these and other important issues, an attempt to outline the major issues and alternatives that should be examined is made. In addition, some suggestions as to potential paths to follow are provided.
Percent Time-Spent-Following as Performance Measure for Two-Lane Highways
Authors: Luttinen R. Tapio
Published: April 2007

The 2000 Highway Capacity Manual (HCM) uses percent time-spent-following (PTSF) as the primary level-of-service (LOS) measure for two-lane highways. On Class I highways, average travel speed is used as an auxiliary measure. The new HCM provides methods for both twoway and directional estimation of PTSF, although the methods are not totally compatible. On Finnish two-lane highways, PTSF is lower than that estimated by the HCM 2000 methodology. Also, the impact of directional distribution is greater, whereas the impact of no-passing zones is less. From the beginning of the motorized transportation era, traffic engineers have searched for methods to define the traffic capacity of highways. Capacity estimation is not enough, however; traffic engineers and road users are both interested in the quality of traffic flow. After almost a century, this search is not yet over. In fact, transportation telematics has increased the need for reliable descriptions of quality traffic flow by using performance measures and concepts that are easily understood by road users. Several performance and service measures (to assign a LOS) suggested for two-lane highways are discussed. The properties of PTSF are discussed in more detail because PTSF has been the most important service measure for two-lane highways since HCM 1985. The estimation of PTSF and its adjustment for prevailing conditions in HCM 2000 are compared by the use of data from Finland. Finally, the applicability of PTSF as a service measure is evaluated against a set of qualifications.
Multimodal Level-of-Service Analysis at Planning Level
Authors: Guttenplan Martin , Landis Bruce W. , Crider Linda , McLeod Douglas S.
Published: April 2007

Methods of determining the level of service (LOS) to scheduled fixed-route bus users, pedestrians, and bicyclists on arterials and through vehicles are presented. The research is based on LOS research for the individual modes and uses a comprehensive arterial approach based on research conducted in Florida. The Florida Department of Transportation (FDOT) developed a multimodal LOS analysis process to measure and provide mobility for diverse roadway users. In 1999 the Florida legislature authorized creation of multimodal transportation districts. It also directed FDOT to develop methods for the measurement of performances of various transportation modes to assist local governments with concurrency requirements for growth management. The Highway Capacity Manual’s (HCM) assessment of arterial LOS does not describe the quality of transportation service provided by the facility as much as it describes the quality of service provided to the through vehicle (automobile) users on the facility. Although this concept does address the primary mode of travel, it does not address the service that the arterial provides to other major potential modes (e.g., transit, walking, bicycling) or allow a multimodal LOS analysis. In the 2000 HCM, LOSs for pedestrians and bicyclists are essentially based on how crowded the respective modal facilities are. However, recent research on quality of service for pedestrians and bicyclists indicates that the most important factors are the lateral separation of the mode and motorized vehicle volume, speed, and type and frequency of transit service. FDOT’s research has applied these models with planning-level assumptions.
Shock Wave and Cumulative Arrival and Departure Models: Partners Without Conflict
Authors: Hurdle V. F. , Son Bongsoo
Published: April 2007

The shock wave and cumulative arrival and departure curve techniques are staples of traffic analysis, particularly for the modeling of freeway congestion, but the literature contains numerous suggestions that they are not compatible. Three numerical examples illustrate that although the two models define queue lengths in different ways, they are compatible, yield identical estimates of travel time and delay, and provide additional insight into the nature of freeway congestion when used together instead of individually.
Freeway Network Simulation and Dynamic Traffic Assignment with METANET Tools
Authors: Wang Yibing , Messmer Albert , Papageorgiou Markos
Published: April 2007

Traffic flow simulation and user-optimal dynamic traffic assignment (DTA) in complex freeway networks are considered. For the DTA calculation, feedback laws of the bang-bang, proportional, proportional plus integer (PI) types, and iterative algorithms that use Frank–Wolfe or PI updating formulas are investigated. Recently, METANET, a macroscopic simulation program for freeway networks, was extended to include generic feedback DTA calculation, whereas METANETDTA, a new METANET derivative, which uses iterative DTA calculation, was developed. Respective program structures and DTA functions are described. Simulation results demonstrate the DTA functions of extended METANET and METANET-DTA.
Multivariate Vehicular Traffic Flow Prediction: Evaluation of ARIMAX Modeling
Authors: Williams Billy M.
Published: April 2007

Short-term freeway traffic flow forecasting efforts to date have focused on predictions based solely on previous observations at the location of interest. This univariate prediction is useful for certain types of intelligent transportation system (ITS) forecasts, such as operational demand forecasts at system entry points. In addition, data from upstream sensors should improve forecasts at downstream locations. This motivates investigation of multivariate forecast models that include upstream sensor data. A candidate model is transfer functions with autoregressive integrated moving average errors, otherwise known as the ARIMAX model. The ARIMAX model was applied to motorway data from France that had been the subject of previous traffic flow forecasting research. The results indicate that ARIMAX models provide improved forecast performance over univariate forecast models. However, several issues must be addressed before widespread use of ARIMAX models for ITS forecasts is feasible. These issues include the increased complexity of model specification, estimation, and maintenance; model consistency; model robustness in the face of interruptions in the upstream data series; and variability in the cross-correlation between upstream and downstream observations. The last issue is critical because ARIMAX models assume constant transfer function parameters, whereas the correlation between upstream and downstream observations vary with prevailing traffic conditions, especially traffic stream speed. Therefore, further research is needed to investigate model extensions and refinements to provide a generalizable, self-tuning multivariate forecasting model that is easily implemented and that effectively models varying upstream to downstream correlations.
Nonlocal Continuous-Space Microscopic Simulation of Pedestrian Flows with Local Choice Behavior
Authors: Hoogendoorn Serge P. , Bovy Piet H. L.
Published: April 2007

Compared with vehicular traffic, pedestrian flow operations are very complex. This is why vehicular flow simulation modeling approaches are generally not applicable to the description of pedestrian flows. Gaining insights into pedestrian flow operations is important in, for instance, the planning and geometric design of pedestrian infrastructural facilities. Additionally, management of pedestrian flows requires knowledge of pedestrian flow behavior. Motivated by the need for accurate pedestrian flow models, a microscopic pedestrian flow model is presented. The model is characterized by pedestrian interaction behavior, based on stimulus-response mechanisms. Moreover, local route-choice behavior is included, which describes how pedestrians choose their direction on the basis of, among other things, their destination and local pedestrian flow conditions. The choice behavior is based on the concept of subjective utility maximization. Moreover, the model features parallel updating, comparable with recently developed cellular automata models for pedestrian flows. However, contrary to these models, pedestrian locations are not bounded to discrete cells. The model can therefore easily describe multidirectional pedestrian flows (e.g., unidirectional, bidirectional, and crossing). Application of the model to a simple hallway is discussed. Besides speed-density relations, self-organizing phenomena are studied in pedestrian flows (dynamic lane formation and clustering) from the microscopic pedestrian flow model.
Toward an Integrated Model of Driver Behavior in Cognitive Architecture
Authors: Salvucci Dario D. , Boer Erwin R. , Liu Andrew
Published: April 2007

Driving is a multitasking activity that requires drivers to manage their attention among various driving- and non-driving-related tasks. When one models drivers as continuous controllers, the discrete nature of drivers’ control actions is lost and with it an important component for characterizing behavioral variability. A proposal is made for the use of cognitive architectures for developing models of driver behavior that integrate cognitive and perceptual-motor processes in a serial model of task and attention management. A cognitive architecture is a computational framework that incorporates built-in, well-tested parameters and constraints on cognitive and perceptual-motor processes. All driver models implemented in a cognitive architecture necessarily inherit these parameters and constraints, resulting in more predictive and psychologically plausible models than those that do not characterize driving as a multitasking activity. These benefits are demonstrated with a driver model developed in the ACT-R cognitive architecture. The model is validated by comparing its behavior to that of human drivers navigating a four-lane highway with traffic in a fixed-based driving simulator. Results show that the model successfully predicts aspects of both lower-level control, such as steering and eye movements during lane changes, and higher-level cognitive tasks, such as task management and decision making. Many of these predictions are not explicitly built into the model but come from the cognitive architecture as a result of the model’s implementation in the ACT-R architecture.
Model for Situation Awareness and Driving: Application to Analysis and Research for Intelligent Transportation Systems
Authors: Matthews Michael L. , Bryant David J. , Webb Robert D. G. , Harbluk Joanne L.
Published: April 2007

The concept of situation awareness (SA)—applied broadly over the last decade to human factors issues in aviation, nuclear power generation, and military combat systems—has only recently been introduced to the analysis of driver behavior. In a driving context, SA involves spatial, temporal, goal, and system awareness. These aspects of SA have been integrated into a goal-oriented model of driver behavior that encompasses strategic, tactical, and operational goals of driving. Maintenance of appropriate SA for each type of goal is based on three underlying processes: perception, comprehension of disparate information, and projection and prediction. The model can be used as a basis for understanding the possible impact of new generations of intelligent transportation systems (ITSs) on driver performance. The model allows ITSs to be analyzed for how they are likely to enhance or impair a driver’s performance in pursuit of each type of driving goal. The model may provide a way to determine how an ITS supports or interferes with the required SA to meet a driving goal (e.g., an onboard navigation system that assists strategic decisions).
Radar Detection of Vehicles in a String: Gaining Situation Awareness of a Propagating Conflict
Authors: Ervin Robert , Bogard Scott , Fancher Paul S.
Published: April 2007

A database of empirical driving measurements is employed to compute the situation awareness benefit of a driver-assistance function that uses the ability of radar to detect targets several deep in a string of vehicles ahead in the same lane. The database resulted from a new roadside video imaging method that has yielded the complete X-Y trajectories, state response variables, and intervehicular motion relationships of 30,500 vehicles on a segment of five-lane arterial street. These data were compiled as a relational database, and queries were run for detecting all cases in which a string of three vehicles is disturbed by a conflict that arises in the leading vehicle pair. Computations reveal, through distributions of the actual motion responses, the larger time cushion that would be available if any following driver in a string became aware of an impending headway conflict as soon as it develops ahead of the preceding vehicle. Results show the value to the following driver that might accrue from a crash-warning function that employs such anticipatory detection. The results indicate that the threat of rear-end crashes in vehicle strings could be mitigated by driver-assistance devices that sense range and range-rate relationships several deep in the string. Because most modern radar technologies have some degree of this capability but do not use it, the results encourage the development of crash-warning applications based on the look-ahead feature.
Synthesis of Studies on Speed and Safety
Authors: Feng Chunxia
Published: April 2007

Studies on the relationship between speed and safety are compiled, and an overview of research interests in the United States and elsewhere is presented. Aspects that affect speed and safety are considered. Techniques for speed management are summarized. The studies are summarized, and conclusions are drawn.
Study of Radar Detector Use on Georgia Highways
Authors: Simas de Oliveira Marcelo G. , Geisheimer Jonathan , Greneker Eugene F. , Leonard John D.
Published: April 2007

Police radar is known to have an effect on the speed of drivers. This effect derives from the presence of vehicles equipped with radar detectors in the traffic stream. The most common method for determining radar detector use is visual examination of the traffic stream. Other methods employ specially developed receivers, often called radar detector detectors. As a response to the development of such a radar detector detector, radar detector manufacturers inserted countermeasures in their designs with the objective of avoiding their detection. Presented is the Georgia Institute of Technology Research Institute radar detector detector, which was developed by using advanced surveillance technology and handles the countermeasures of current radar detectors. This system was used to determine radar detector densities at three sites (rural two-lane road, four-lane state route, and six-lane Interstate) around the Atlanta, Georgia, metro area. The data collected were analyzed and compared against commonly used statistical probability distributions. Common distributions were fitted to the data, whenever appropriate. The determined radar densities by site and time of day were compared by using a nonparametric analysis of variance test. This analysis revealed that facility type has a significant impact on radar detector density, whereas time of day showed a significant effect for only one of the sites (state route).
Accessibility in a Metropolis: Toward a Better Understanding of Land Use and Travel
Authors: Kitamura Ryuichi , Akiyama Takamasa , Yamamoto Toshiyuki , Golob Thomas F.
Published: April 2007

An attempt was made to determine how accessibility affects aspects of long-term and short-term travel behavior. The accessibility indices that were used represent the ease with which opportunities for engagement in activities can be reached from a geographical zone in an urban area. The behavioral aspects examined include engagement in activities, automobile ownership and use, and travel patterns as represented by the number of trips, number of trip chains, and total travel time expenditure. Data from the Kyoto-Osaka-Kobe metropolitan area of Japan and the southern California coast are used to examine the following conjectures: time availability is more closely associated with engagement in activities than accessibility; accessibility no longer affects automobile ownership or use in the metropolises of industrialized countries where motorization has matured; and given automobile ownership and use, travel patterns are conditionally independent of accessibility.
Stated Preference Analysis of Sensitivities to Elements of Transportation and Urban Form
Authors: Hunt J. D.
Published: April 2007

A total of 1,277 randomly selected households in Edmonton, Alberta, Canada, were successfully interviewed concerning their attitudes to a range of elements of urban form and transportation. These elements included times and costs for trips to work and shopping by automobile and transit, taxes, air quality, traffic noise, walking conditions to local schools, street type in front of dwelling, and housing type. A stated preference technique was used, in which each respondent was asked to rank in order of preference a set of hypothetical future alternatives involving the elements. Additional direct questions were then asked about the influences of the elements in the ranking process. Logit choice analysis was used to establish the relative importance of each element for the “typical” household represented by the full sample and for various groups in the population represented by different subsamples. Overall, it was found that housing type is the most important of the elements considered, followed by municipal taxes, air quality, and traffic noise. Also, among many other things, there is less sensitivity to money spent for travel than to money paid for taxes. These indications, together with the various specific trade-off rates that were obtained, provided useful guidance in the development of a new transportation master plan. They can also support a more formal evaluation system that reflects the sensitivities of different groups of households regarding a wide range of elements of concern to transportation and urban planners. The techniques used are flexible and could be used to consider various other elements of concern in different contexts.
Analysis of the Resident Component in PennPlan’s Public Involvement Survey: Survey Overview and Item Nonresponse Selectivity Issues
Authors: Kim Tae-Gyu , Koza Sandy A. , Goulias Konstadinos G.
Published: April 2007

As part of the public involvement initiative undertaken for Pennsylvania’s new long-range transportation plan (PennPlan), an attitudinal survey was administered to a sample of residents in the state. A few survey issues and an in-depth analysis of the survey questions are summarized. Information is provided on ( a) the purpose of the survey, its components, and underlying themes; ( b) the administration of the survey, its advantages and disadvantages, and possible solutions to improve the survey administration process; and ( c) an in-depth analysis of the grades and importance ratings assigned to various aspects of the existing transportation system. The last issue receives particular emphasis. To compensate for the large number of nonresponses and the systematic response for the grades and importance ratings, the analysis was done in two steps. The first step uses sample selectivity to determine if systematic patterns existed between the residents who did and the residents who did not assign grades and importance ratings to certain aspects of the existing transportation system as functions of personal and residence characteristics. The results of this step were then used to “adjust” the coefficients in an ordered probit regression model that explains resident grades and importance ratings for the valid responses. By doing this, the models can account for the systematic nonresponse and yield models of responses on the basis of which unbiased inferences can be made.
Port of Pittsburgh Practicum Project
Authors: Bytnar Linda , Chiu Andrew , Frommann Isabelle , Gruwell Linda , Guttman Lissa , Morgan Wade
Published: April 2007

In the past few years traditional business strategies have been significantly challenged by the Internet and e-commerce. Although old-economy companies dominate the transportation industry now, the industry is poised for change. Recent forecasts still predict explosive growth in business-to-consumer and business-to-business e-commerce. Without doubt, a shift from the traditional business model must include an Internet strategy and a viable aspect of e-commerce to secure a competitive advantage. Recognizing those macroeconomic trends, the Port of Pittsburgh Commission (PPC) engaged the Carnegie Mellon University practicum team to evaluate and recommend an e-commerce solution. SmartBarge offers PPC the results of the practicum team’s efforts. The approach taken was to create a technical solution enabling shippers and providers to connect seamlessly and open a dialogue. By increasing both the sponsor’s understanding of the range of issues involved and the support of key industry leaders, the team has allowed PPC to strategically position itself for a subsequent step in the near future. Registration of the domain name SmartBarge.com by PPC was a plus for the practicum team. The name can be easily remembered and used to build a theme for the new website. The website is a working model that will allow PPC to build awareness of barge transport and to create a dialogue with shippers and waterway service providers. Although robust in functionality, it is only a first step to defining the requirements of a longer-term website that will handle end-to-end commercial transactions spanning the entire barging process.
Application of Reengineering Techniques in Redesign of Port Processes
Authors: Giannopoulos G. A. , Papageorgiou K.
Published: April 2007

Basic findings and recommendations of a 3-year research project are presented. The project deals with the application of business process reengineering methods to small- and medium-sized ports as a way of achieving overall effectiveness of port processes, as well as producing port-user benefits of all kinds. The project adopted a customer-oriented process view for tackling the problems faced. It produced a number of “tools” and work guidelines that port authorities can use to reconsider and review their processes with a view to changing (reengineering) them to increase efficiency. The basic premise and reasoning behind the work was that simply applying advanced technology to current port processes does not produce dramatic improvements. Normally these processes are fragmented, that is, they lack transparency and continuity because a variety of entities with seemingly conflicting interests are involved. To overcome this fragmentation and maximize the possibility of synergetic effects, a dynamic reconfiguration of the whole port system (i.e., the processes, entities involved, and their interrelations) is suggested. A brief review is presented of tools that were produced. Also described are specific generic reengineering solutions for port processes that resulted from the work, based on the suggested dynamic port system configuration.
Modeling the Internal Transport System in a Containerport
Authors: Garrido Rodrigo A. , Allendes Felipe
Published: April 2007

Containerport operations consist of five components: navigation system, loading/unloading, container transfer, storage, and land interface. Usually, an analysis of port operations is performed through discrete simulation. An alternative modeling approach that jointly addresses three of the five components is presented. Internal transport is composed of three consecutive stages: unloading a container, transferring it to a yard, and finally placing it within a yard; this cycle operates in the reverse direction also. The main objective is to present an analytical tool to analyze the effect of different internal transport strategies on the efficiency of a containerport. The analytic model is based on queuing theory and relies on operational parameters such as fleet size, fleet configuration, capacity and configuration of cranes, speed of empty and full terminal tractors, and variations in travel distance between the wharf and storage yard. The analytic model allows the computation of terminal efficiency as a function of the effective capacity of container transference when any of the operational parameters change. The operational parameters mentioned above were obtained from an actual scenario at the port of San Antonio, Chile. A discrete simulation model was implemented to act as a validation benchmark. Results showed that the analytic model was a fairly accurate representation of the studied phenomenon, as well as an easy-to-use tool in assisting port operators with decision-making tasks.
Managing Containers in a Marine Terminal: Assessing Information Needs
Authors: Jones Elizabeth G. , Walton C. Michael
Published: April 2007

The research addresses questions about how intelligent transportation systems technologies that are being used to track and manage containers in transit can also be used to manage the stacked storage of containers in marine terminals. The research focuses on import container storage. The objective is to assess whether and how more accurate and timely information about the departure times of containers can be used to more efficiently and effectively manage import containers in stacked storage. An “informed” import storage strategy along with performance analyses of this strategy in relation to typical storage strategies used by ports is presented. The strategy for organizing import stacked storage is described. The study methodology used and subsequent analysis of these options regarding performance and economics follow. Results indicate that using a reservation system similar to the crescent system used by the port of New Orleans would significantly reduce import container–handling efforts. The system would enable a port operator to gather enough information about when import containers would leave the port to allow careful ordering of import container storage, which would result in reduced handling.
Modeling Competitive Transit and Road Traffic Information Services with Heterogeneous Endogenous Demand
Authors: Yang Hai , Zhang Xiaoning
Published: April 2007

A new equilibrium model is proposed to determine the equilibrium market penetration of the advanced traveler information system (ATIS) in a network with heterogeneous users and elastic demand. User heterogeneity is considered by assuming a continuously distributed value of time (VOT) across users, and demand elasticity is considered by using a deterministic mode choice model for public transit and for equipped and unequipped private cars. The user equilibrium of mode choices for a given ATIS service charge, transit fare, and frequency is so determined that no one can reduce his or her generalized travel cost by changing to an alternative travel mode according to his or her own VOT. Furthermore, assuming provision of ATIS and transit services by competitive profit-maximizing firms, the market equilibrium is studied using game theory by determining each firm’s service charge and service quality and its resultant market shares. Through numerical simulation, the benefits generated from a given combination of service charges and service qualities to transit and road users, transit and ATIS service providers, and society as a whole are investigated.
Analysis of Crash Precursors on Instrumented Freeways
Authors: Lee Chris , Saccomanno Frank , Hellinga Bruce
Published: April 2007

Traffic flow characteristics that lead to crashes on urban freeways are examined. Since these characteristics are observed prior to crash occurrence, they are referred to as “crash precursors.” The objectives are ( a) to explore factors contributing to changes in crash rate for individual vehicles traveling over an urban freeway and ( b) to develop a probabilistic model relating significant crash precursors to changes in crash potential. The data used to examine crash precursors were extracted from 38 loop detector stations on a 10-km stretch of the Gardiner Expressway in Toronto for a 13-month period. An aggregate log-linear model was developed relating crash rates to the selected crash precursors observed upstream of the crash site. The results of this analysis suggest that the variation of speed and traffic density are statistically significant predictors of crash frequency after controlling for road geometry, weather, and time of day. With the model, crash potential can be established based on the precursors obtained from real-time traffic data.
Allocating Track Maintenance Costs on Shared Rail Facilities
Authors: Resor Randolph R. , Patel Pradeep K.
Published: April 2007

Railroads were originally conceived as public highways on which anyone might operate. This idea rapidly demonstrated its impracticality, and for many years railroads in most of the world have controlled both infrastructure and operations. However, the European Union is moving toward an open access model for railroads in which track ownership (and related functions, such as train dispatching) is required to be separate from train operations. Separate ownership and operations will require some method for establishing access charges. The fundamental issue is how costs are to be shared among multiple users of a single rail line. At the simplest level, costs can be assigned based on the volume of traffic. But what measure should be used—gross tonnage, train hours, or number of trains? TrackShare is a cost-allocation model that has been developed to meet this need. The process of applying TrackShare to the National Railroad Passenger Corporation’s (Amtrak’s) Northeast Corridor to determine the cost of operating rail freight traffic is described.
Using Simulation to Evaluate Rail Sleeper Replacement Alternatives
Authors: Lake Maree , Ferreira Luis , Murray Martin
Published: April 2007

A simulation model developed to enable a cost-benefit analysis of sleeper-replacement strategies, using the Weibull distribution, has been updated from a previous version to include up to four different types of sleepers within the track section: steel, concrete, treated timber, and untreated timber. In addition, several changes have greatly increased the number of strategies that can be simulated. The creation of a replacement strategy has been substantially developed to include two separate components, many new frequency and policy options, and the option of continuing a completed simulation with a modified replacement strategy. The model output is designed to give adequate information to the operator to determine the best course of action to take when comparing various possible replacement strategies. The results include the track condition, with the clusters of failed sleepers, and the cost of the replacement strategy. Five distinctly different replacement strategies were simulated for 20 years on a track section with 50,000 mature sleepers. These simulations showed that the nature of the strategy can have very significant effects on the cash flow required from year to year and on the annual demand for replacement materials. Careful investigation is needed to establish compromise strategies that produce acceptable numbers and sizes of clusters of failed sleepers and sleeper life in track while not exceeding available funding and materials.
Best-Practice Truck-Flow Estimation Model for the New York City Region
Authors: List George F. , Konieczny Laura A. , Durnford Chanda L. , Papayanoulis Vassilios
Published: April 2007

A model that can estimate a truck-trip matrix for a large metropolitan area is under development for the New York City region. The model is part of a new suite of demand-forecasting tools intended to bring the analytical capabilities of the region up to best practice worldwide. At the heart of the model is a gradient-based optimization technique that seeks to create a trip matrix that best fits a set of input data. The model allows great flexibility in both the types of data that can be introduced and the functional form of the objective function. The model is supported by two submodels. One estimates trip generations and attractions by zone, and the other provides link-use probabilities based on a multiple-path traffic assignment. The model and its application to the New York City regional network are described.
Heuristic Analysis of Impacts of Commuter Rail Station Consolidation on Pedestrian Access
Authors: Ayvalik Cemal K. , Khisty C. Jotin
Published: April 2007

A mode-of-station-access survey at the Milwaukee District North Line Grayland and Mayfair Stations in Chicago is described. The study was conducted to determine the impacts of consolidating these two stations into a single new station. Patterns of different station access modes were studied. The analysis focused on the most sensitive market segment—walkers. Two different methods were used to determine how current walkers would be affected by such a station change. The first estimate was based on changes in walking distances. A heuristic procedure was developed to estimate the number of walkers currently using the system who would possibly walk to the proposed new station. This estimate assumed that stations would attract walkers from a circular area referred to as the catchment area. The average walking distance to each station determined its catchment area size. Further assumptions were made to predict those walkers who were not currently in the catchment areas but who would decide to walk to the new station. This study provides intuitive results and methodology that show promise for use in similar situations.
Effectiveness of Condition-Responsive Advisory Speed Messages in Rural Freeway Work Zones
Authors: McCoy Patrick T. , Pesti Geza
Published: April 2007

Condition-responsive advisory speed messages were evaluated as part of the Midwest States Smart Work Zone Deployment Initiative, a pooled-fund study sponsored by Iowa, Kansas, Missouri, Nebraska, and FHWA. The messages were displayed on three portable changeable message signs (PCMS) placed approximately 1.61 km (1 mi), 4.83 km (3 mi), and 12.87 km (8 mi) ahead of a work zone on a rural interstate highway in Nebraska. The messages were intended to advise drivers of the speed of slower traffic ahead and thereby encourage them to slow down. Speeds downstream of the PCMSs were measured and compared with the speeds displayed in the messages. The results of the analysis indicate that the messages were somewhat effective in reducing speeds. Their effectiveness could have been improved if the distances between the PCMSs had been shorter and thus the message locations would have been closer to the points with lower traffic speeds. Driver interviews revealed that the advisory speed messages were understood and thought to be useful by most drivers who had seen them. However, some drivers questioned their usefulness and doubted their reliability, because they had not seen any reason to slow down.
Distribution and Characteristics of Crashes at Different Work Zone Locations in Virginia
Authors: Garber Nicholas J. , Zhao Ming
Published: April 2007

Work zones tend to cause hazardous conditions for drivers and construction workers, because they create conflicts between construction activities and traffic, thus exacerbating the existing traffic conditions. Every effort should therefore be made to minimize the negative impacts of work zones. A clear understanding of work-zone crash characteristics will help to determine appropriate measures to minimize work-zone hazards. This study investigated the characteristics of work-zone crashes that occurred in Virginia from 1996 through 1999. The information on each crash was obtained from police crash records. Each crash was located in one of five areas of the work zone—( a) advance warning, ( b) transition, ( c) longitudinal buffer, ( d) activity, and ( e) termination. The percentage distributions were analyzed relative to crash location, crash severity, collision type, and highway type. The proportionality test was used to determine significant differences at the 5% significance level. The results indicate that the activity area is the predominant location of work-zone crashes regardless of highway type, and rear-end crashes are the predominant crash type. The results also indicate that the proportion of sideswipe-in-same-direction crashes in the transition area is significantly higher than that in the advance warning area.
Analysis of Bituminous Crack Sealants by Physicochemical Methods: Relationship to Field Performance
Authors: Masson J.-F. , Collins Peter , Margeson Jim , Polomark Gary
Published: April 2007

Bituminous crack sealants were analyzed by viscometry, fluorescence microscopy, infrared spectroscopy, thermogravimetry, modulated differential scanning calorimetry, and low-temperature tensile testing. The results indicate that sealants are blends of bitumen, oil, copolymer, and filler. Upon blending, these components produce a three-phase system that consists of a polymer-modified bitumen (PMB) matrix, a filler, and a filler-PMB interface. Spectroscopy and microscopy indicate that the PMB phase is rich in styrene-butadiene copolymer, that the filler is recycled rubber, sometimes mixed with calcium carbonate, and that the interface depends on the filler and the oil content in the sealant. The physicochemical methods were used to predict the short- and medium-term performance of sealant mixtures. The short-term performance predicted from viscometry and microscopy correlated well with the 1-year field performance of the sealants. Sealants showed two glass transition temperatures ( Tg’s), and a reasonable correlation was also found between low Tg and medium-term performance in a wet-freeze climate. However, because Tg measurements do not account for stress relaxation and aging effects, correlation was not perfect.
Influence of Key Parameters on Quality of Dry-Mix Shotcrete
Authors: Abou-Zeid Mohamed Nagib , Elkhidir Elrasheid M.
Published: April 2007

Two main shotcreting processes exist. In the dry-mix process, all the components are mixed dry, and then a jet of water is added to the mixture as it leaves the shooting nozzle. In the wet-mix process, components are mixed wet and then shot through the nozzle. However, relatively few data are pertinent to factors that have a vital effect on the shotcrete quality when the shotcrete is applied using prepackaged (preprepared) materials or materials prepared on site. The effects of several parameters on the quality of dry-mix shotcreting were investigated: shooting distance, water-to-cementitious materials ratio, and mix proportion. Panels were shotcreted using conventional on-site mixtures and prepackaged mixtures. Cores were extracted from the surface, and beams were sawed from the panels for testing. Concrete absorption, concrete unit weight, rebound losses, compressive strength, flexural strength, and Schmidt (rebound) hammer tests were performed on both mixtures. Results indicate that the overall quality of the prepackaged material is superior to that of the on-site mix. They also suggest that a shooting distance exists at which mechanical properties as well as losses may be at an optimum. Findings strongly indicate that the traditional nondestructive tests (e.g., Schmidt hammer and ultrasonic pulse velocity) should be applied to shotcrete with some precautions because of changes in the nature of the concrete surface. Additional work should be carried out to elaborate on the shotcrete parameters and investigate their effects when other parameters and techniques are implemented.
Policies and Practices for Cost-Effective Transit Investments: Recent Experiences in the United States
Authors: Deakin Elizabeth , Ferrell Christopher , Mason Jonathan , Thomas John
Published: April 2007

A structured survey of transit agency staff and interviews with agency executives and other local leaders were conducted in areas that have undertaken a major transit investment project in the past 5 years. The purpose was to identify methods and procedures used to evaluate and select projects and, in particular, to document how land use considerations are being incorporated into project decisions. Staff members responsible for 41 projects were contacted, and 28 completed the survey, discussing projects in 23 regions of the United States. Supplementary interviews were conducted for 10 of the regions. The study found that most agencies use federal guidance and regulations on the evaluation of transit investment as a starting point, but give equal weight in project design and selection to state and local policy objectives such as social equity, economic development, and fair-share distribution of projects among local communities. A number of transit agencies give priority to projects in jurisdictions with transit-supportive land use patterns or plans. The availability of public or private funding contributions is increasingly important in prioritizing projects. Increasingly, transit agencies are hiring staff to work with local governments on land use planning and on funding partnerships and are working with them to develop a shared understanding of the area’s transit needs and related development objectives. Staff and political leaders deem these efforts at least as important as technical evaluations of cost-effectiveness.
Benefits of Pilot Implementation of Public Transport Signal Priorities and Real-Time Passenger Information
Authors: Lehtonen Mikko , Kulmala Risto
Published: April 2007

A public transport telematics system was launched in Helsinki, Finland, in 1999. The system provides several public transport telematics functions such as real-time passenger information, bus and tram priorities at traffic signals, and schedule monitoring. The impacts, socioeconomic benefits, and technical performance of the telematics applications were investigated. The methods included before-and-after field studies, an interview and survey, a simulation, and socioeconomic evaluation. The results indicate that delays at signals were reduced by more than 40%. The regularity and punctuality of the service were considerably improved. On both lines, the number of passengers increased from the level before the system was implemented. The studies indicated reductions of 1% to 5% in fuel consumption and exhaust emissions. The information systems were regarded very positively, and the systems were considered useful. In particular, the information displays on stops were considered necessary and were used often. Most effects were more substantial on the bus line than on the tramline because of the longer intervals between buses and the fact that the tramline already had signal priorities before the system was introduced. The benefit–cost ratio of the system was calculated to be 3.3. For the transport operator, the return on capital increased by 6% on the bus line and decreased by 1% on the tramline.
Development of Time-of-Day–Based Transit Accessibility Analysis Tool
Authors: Polzin Steven E. , Pendyala Ram M. , Navari Sachin
Published: April 2007

The measurement of transit accessibility and availability is important both for forecasting transit ridership and for planning and evaluating transit service. When measuring transit accessibility, both spatial and temporal dimensions of demand and supply are important considerations. Between these two dimensions, the temporal dimension has lagged behind the spatial dimension with respect to its explicit recognition and incorporation in transit accessibility measurement. A transit accessibility measurement tool has been developed that explicitly considers two facets of the time dimension. Considered first is the supply side of the time dimension by incorporating the span and headway of service and the willingness to wait to determine the actual time duration when service is truly available to potential riders. Next considered is the demand side of the time dimension by incorporating the time-of-day distribution of travel demand to determine the relative value of the transit service provided in each time period of the day. The tool measures transit availability with regard to the daily trips per capita in each zone that is exposed to transit service. The flexible spreadsheet-based tool can be easily and quickly applied at the local level in support of service planning and service delivery analysis. The application of the tool is demonstrated with a simple numerical illustration.
Multilevel Network Optimization for Public Transport Networks
Authors: van Nes Rob
Published: April 2007

Most studies on public transport network design deal with single-level networks only. Urban public transport networks, however, not only offer transport services to and from the city center but also to stations of interurban public transport networks. A population’s use of both types of public transport services implies a dependency between these networks. An analytical model was developed to analyze this dependency for two connected networks. For each network, the operator will adopt a certain objective in optimally designing the network. An analysis was made for the cases in which a single operator is responsible for both networks, or in which two different operators run each network. In all cases the objectives of profit maximization and welfare maximization were used. In the two-operator case, each operator may follow its own objective. The different scenarios led to sensibly different values for stop spacing, line spacing, and frequencies. For interurban public transport companies it appears to be profitable to cooperate with urban public transport companies or to pursue a strategy for local authorities to adopt the objective of welfare maximization for urban public transport network design. In the case of welfare maximization, that is, the authorities’ perspective, the impact of two operators instead of a single operator is nearly negligible. The combination of welfare maximization for the urban public transport network and profit maximization for the interurban network indirectly subsidizes interurban public transport. These findings provide interesting insights for authorities responsible for commissioning public transport services.