bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Artificial Neural Networks to Predict Speeds on Two-Lane Rural Highways
Authors: McFadden John , Yang Wen-Tai , Durrans S.
Published: April 2007

The ability to predict accurately vehicular operating speeds is useful for evaluating the planning, design, traffic operations, and safety of roadways. Operating speed profile (OSP) models are used in the geometric design of highways to evaluate design consistency. Design consistency refers to the condition where the geometric alignment does not violate driver expectations. Existing OSP models have been developed using ordinary linear regression methods. However, the assumptions and limitations inherent to linear regression may at the very least complicate model formulation. If not acknowledged and corrected for, deviations from these assumptions can also adversely affect the efficacies of such models. Artificial neural networks (ANNs) are modeling tools that do not impose the stringent assumptions and limitations imposed by regression. It is therefore of interest to know whether ANNs are viable alter natives to linear regression for OSP modeling. Two backpropagation ANNs for operating speed predictions for passenger cars on two-lane rural highways are evaluated, and their performances with regression-based models are compared. The results of these comparisons indicate that the explanatory powers of the ANN models are comparable with those developed by regression. The predictive powers of the two types of models were observed to be comparable, and ANNs were not limited by distributional or other constraints inherent to regression. Therefore, ANNs were determined to be a viable alternative to regression for OSP model construction.
Speed Behavior Analysis at Curved Ramp Sections of Minor Interchanges
Authors: Liapis Evangelos D. , Psarianos Basil , Kasapi Eva
Published: April 2007

On and off ramps act as interfaces between freeways and the surface street network (nonfreeway highways) and in effect should provide a smooth and safe transition from one facility to another. The speed behavior of passenger cars at minor-interchange on and off ramps with unusual curved arrangements is analyzed in depth for the first time. Vehicle speed data were collected at 20 on and off ramps in Greece that have a variety of geometric features. Regression analyses were applied to investigate the variables affecting operating speed— V85. The best models resulted in coefficients of determination of nearly 0.75, indicating that operating speed is influenced by curvature change rate and superelevation rate. Comparison of the “Greek speed profile” with those of Australia, Austria, Germany, South Africa, and the United States proved that for on and off ramps it very closely approximates the values of Australia, Austria, and Germany. Austria is the only country using V85 to determine ramp geometrics. The differences between the Greek V85 and the speed values recommended by the German guidelines are considered small, ranging from 6 to 9 km/h for on ramps and −1.5 up to −4 km/h for off ramps. The analysis produced regression models that will provide designers with a tool to estimate the operating speed during the design process.
Travel Time Comparisons Between Seven Unconventional Arterial Intersection Designs
Authors: Reid Jonathan D. , Hummer Joseph E.
Published: April 2007

Signalized intersections on high-volume arterials are often congested during peak periods, causing a decrease in through movement efficiency on the arterial. Much of the vehicle delay incurred at conventional arterial intersections is caused by high left-turn demand. Unconventional intersection designs attempt to reduce intersection delay and travel times by rerouting left turns away from the main intersection. Seven unconventional designs—the quadrant roadway intersection, median U-turn, superstreet median, bowtie, jughandle, split intersection, and continuous flow intersection designs—that could apply to a wide range of standard, four-leg intersections are compared. Previous comparisons of intersection delay and travel time between conventional designs and these unconventional designs have been piecemeal and have largely used hypothetical volumes. Simulation experiments were conducted using turning movement data from seven existing intersections of varying sizes to compare the travel time of conventional and unconventional designs fairly. Optimum cycle lengths were used for each design, and a number of factors were held constant to keep the comparisons fair. Off-peak, peak, and peak-plus-15-percent volume levels were examined. The results from the simulations showed that at each intersection one or more unconventional designs had lower total travel times than the conventional design. Whereas most of the unconventional designs showed improvement in one or more scenarios, the quadrant roadway intersection and the median U-turn designs consistently produced the lowest travel times. When considering the design of high-volume intersections like those tested, engineers should seriously consider quadrant roadway intersection and median U-turn designs where rights-of-way are available.
Multilevel Analysis of Activity and Travel Patterns: Accounting for Person- and Household-Specific Observed and Unobserved Effects Simultaneously
Authors: Goulias Konstadinos G. , Kim Tae-Gyu
Published: April 2007

Activity and travel demand analysis can be greatly improved by a more realistic description of the relationship between activity engagement and trip-making behavior when person and household variation are accounted for jointly. Four activity pattern groups and four travel pattern groups, obtained in the past using cluster analysis and applied to behavioral indicators (e.g., activity frequency and duration), are analyzed using multinomial logit and multilevel multinomial logit (multi-MNL) models. All models include temporal, spatial (residence and workplace), household, and person effects. The multilevel models, designed for hierarchical data structures, also include correlated random components among the pattern options at the household and person levels. First, past research results are confirmed that contextual variables (e.g., household, neighborhood, time) are important explanatory variables for these activity and travel patterns and that temporal effects are much stronger for activity pattern groups than for travel pattern groups. Then, using the multi-MNL models, a complex structure in unobserved heterogeneity is identified in which choices are correlated among some patterns at the household level and among other patterns at the person level. Both travel and activity pattern analyses, however, indicate that unobserved heterogeneity should be accounted for at both levels when regression models are estimated.
Association Rules in Identification of Spatial-Temporal Patterns in Multiday Activity Diary Data
Authors: Keuleers Bertold , Wets Geert , Arentze Theo , Timmermans Harry
Published: April 2007

Activity-based analysis in transportation demand forecasting is one of the most promising approaches in current transportation modeling. Travel decisions are understood as the outcome of underlying scheduling activity, resulting in large-scale interviews generating a large amount of data. Traditional techniques have been shown to be inefficient in describing the dependencies between different attributes if data sets are too large. Associations between data set attributes are described by means of association rules. The discussion outlines the description of activity-based transportation data sets through association rules for identification of spatial-temporal patterns in multiday activity diary data.
Sampling Alternatives from Colossal Choice Set: Application of Markov Chain Monte Carlo Algorithm
Authors: Yamamoto Toshiyuki , Kitamura Ryuichi , Kishizawa Keiko
Published: April 2007

It is often the case that a discrete choice model cannot be applied to forecasting because the choice set is unmanageably large and choice probabilities cannot be evaluated in a practical manner. For example, an activity-based analysis of travel behavior often involves an astronomical number of potential activity travel patterns, resulting in an enormous choice set when one attempts to formulate the behavior as a discrete choice. A colossal choice set makes it practically impossible to define the full choice set and to evaluate the choice probability of each pattern for forecasting. An algorithm is presented for the simulation of individuals’ activity travel choice by sampling activity travel patterns from a colossal choice set, according to their choice probabilities as determined by a discrete choice model without enumeration of the full choice set. Numerical examples demonstrate the practicality and effectiveness of the algorithm in forecasting the effects on activity travel patterns of transportation policy measures.
Drivers’ Route Choice Rules and Network Behavior: Do Drivers Become Rational and Homogeneous Through Learning?
Authors: Nakayama Shoichiro , Kitamura Ryuichi , Fujii Satoshi
Published: April 2007

Most analyses of driver-network transportation systems rest on the presence of network equilibrium. Equilibrium analyses presuppose that the driver is rational and homogeneous and has perfect information. A more realistic view, however, is that individuals’ rationality is bounded because of their cognitive limitations. A driver is assumed to adopt simple rules when he chooses a route. A model system in which the driver’s learning is simulated with multiple rules is applied to investigate the validity of the hypotheses underlying network equilibrium. The results of simulation analyses can be summarized as follows. Drivers do not become homogeneous and rational, as equilibrium analyses presuppose; rather, there are fewer rational drivers even after a long process of learning, and heterogeneous drivers make up the system. Drivers’ attitudes toward and perceptions of each route do not become homogeneous either but become bipolar. The results point to the need for a critical appraisal of the foundation of the equilibrium analysis of network flow.
Dynamic Traffic Analysis with Static Data: Guidelines with Application to Paris
Authors: Marchal Fabrice , de Palma André
Published: April 2007

An innovative approach that uses static origin-destination (O-D) matrices to model travel demand in dynamic urban traffic models is presented. Dynamic traffic assignment models require the use of time-dependent or dynamic O-D matrices whose acquisition and estimation can be costly and whose consistency can prove difficult to maintain, whereas static O-D matrices of overall trip demand have been estimated for various cities during the last decade. In contrast, the synthetic approach describes the user departure time behavior in a separate model that splits the demand specification into two distinct blocks: the departure time behavior and the time-independent trip demand. Pros and cons of this method are presented with an application to the Paris region with the dynamic simulator METROPOLIS. Guidelines for model designers and planners who are considering the shift to dynamic traffic simulation tools are also presented.
Stochastic User Equilibrium Formulation for Generalized Nested Logit Model
Authors: Bekhor S. , Prashker J. N.
Published: April 2007

The route choice problem is complicated in typical transportation networks because of the size of the choice set and because of the overlapping problem since many routes share links. Well-known models like the probit and the logit were further developed in an attempt to overcome these problems. The logit model has the appeal of being relatively close to the probit model while keeping a convenient analytical closed form. However, the simple multinomial logit model cannot correctly represent route choice, especially with respect to the overlapping problem. Other hierarchical logit models can potentially overcome the overlapping problem. The recently developed generalized nested logit (GNL) model is found to be very suitable for route choice, as is the cross-nested logit (CNL) model. The inclusion of the congestion effect in the route choice problem is accounted for in stochastic user equilibrium (SUE) problems. The development of a SUE formulation for the GNL model is presented. In addition, how to adapt the GNL model to route choice in a way similar to that of the CNL model is shown. An equivalent SUE formulation for the GNL model is developed. In this way, a unified framework is presented to relate GNL-type models, which are derived from discrete choice theory, with aggregate entropy formulations. A preliminary algorithm is developed to illustrate the potential application of the GNL formulation for real networks.
Coevolutionary Approach to Extracting and Predicting Linked Sets of Complex Decision Rules from Activity Diary Data
Authors: Arentze Theo , Timmermans Harry
Published: April 2007

A new approach for extracting and predicting decision rules for linked choices is developed and explored for use in computational process models of activity-scheduling and activity-profiling decisions. This coevolutionary approach, represented by a new agent, coevolutionary heuristic algorithm for deriving rules from N-dimensional travel activity links (Chantal), has been implemented in the ALBATROSS model. The algorithm induces sets of decision rules by incorporating the observed choice for all other facets as conditions in the decision table formalism. In the predictive stage, probabilities of activities are iteratively updated until a predefined convergence level is reached. The performance of the coevolutionary approach is compared with independent and sequential modeling approaches. The coevolutionary model turns out never to perform worse and often performs better than the best alternative approach under various conditions.
Shelter from the Storm: Optimizing Distribution of Bus Stop Shelters in Los Angeles
Authors: Law Philip , Taylor Brian D.
Published: April 2007

The functions of bus stop shelters and factors affecting their placement at stops in transit systems are analyzed. Drawing on information from a variety of sources, current shelter placement policy in Los Angeles was found to be guided principally by the revenue-generating potential of shelter advertisements, secondarily by political concerns over geographic equity, and only peripherally on the basis of bus stop use. Using data on shelter and stop locations, boardings, and headways, a methodology is developed for measuring the cumulative use of bus stops with regard to person-min of wait time. Then this measure is used to evaluate three scenarios of bus stop placement, each of which optimizes the goals of ( a) private shelter providers, ( b) locally elected officials, and ( c) bus patrons, respectively. The conclusion is that either of the latter two scenarios would dramatically—by 2.3 person-years each day—increase the time that bus patrons in Los Angeles spend under shelter while waiting for buses at stops. This analysis both demonstrates the utility of using stop-coded boarding data in combination with headway data in the planning of bus stop shelters and shows the ineffectiveness and inequities that can arise when the sheltering of waiting passengers is not explicitly incorporated into policies guiding the placement of transit shelters.
Development of Database for Louisiana Highway Bridge–Scour Data
Authors: Farrag Khalid , Morvant Mark
Published: April 2007

Scour of highway bridges in Louisiana has been collected and monitored since 1970. Approximately 120 bridges are being monitored at a frequency of one to several times per year with an average of six cross sections for each bridge. Consequently, a tremendous amount of scour data in the format of traditional paper files already exists for these bridges. Manual and visual analysis of data has been tedious work, and there existed a need to develop a computer program and a database system to perform scour-data management. Database-management software has been developed for storage, retrieval, and analysis of scour data of Louisiana highway bridges. The system stores the data in a database system within the network. A computer program was developed as a front-end to allow the user to access the database, retrieve the data via several search routines, plot the scour data for analysis, and perform data updates. The program compiles the on-site data collected during scour survey and the bridge data relevant to scour properties. It can be used in ( a) determining local scour at the piers and contraction scour at the bridge, ( b) analyzing the long-term changes in riverbed elevations at various locations in the site, ( c) providing the major parameters that are commonly used in bridgescour models for scour prediction, and ( d) evaluating site conditions and soil properties for scour repair. The program tabulates and plots the bridge information, pier data, and coordinates of the river cross sections at the survey locations. It displays survey maps and soil-boring data. The analysis of the bridge-scour data is performed using plots of the cross sections, longitudinal sections, and contour lines of the scour data. The history of the scour at any specific location is plotted in time plots. Further implementations of the database system are suggested for more accurate determination of potential scours in highway bridges.
Wetting-Induced Settlement of Compacted-Fill Embankments
Authors: Miller Gerald A. , Muraleetharan Kanthasamy K. , Lim Yong Yeow
Published: April 2007

Many highway embankments experience problematic settlements. Compression of soil under the self-weight of the embankment generally occurs during construction, but postconstruction, wetting-induced collapse can result in more long-term settlement problems, depending on climate and movement of the wetting front. A study undertaken to examine settlement associated with unsaturated soil embankments included centrifuge modeling of compacted silt embankments, laboratory testing of the embankment soil, and data interpretation with the focus on settlement prediction. A silty soil was selected to facilitate the measurement of matric suction using tensiometers. Three model embankments were constructed and tested in the Army Corps of Engineers Centrifuge Research Center in Vicksburg, Mississippi. Embankments 20 m high were simulated using centrifugal acceleration of 165 g. Embankments were constructed to achieve a relative compaction of 90 or 95 percent based on standard effort and moisture content between 2 and 5 percent dry of the optimum moisture content. Instrumentation used during self-weight compression and wetting included linear variable differential transformers and pore-pressure transducers equipped with high-air-entry porous stones. Results demonstrate the importance of the as-compacted water content and dry unit weight on the potential for wetting-induced collapse settlement. Settlement caused by self-weight compression and that caused by wetting-induced collapse are clearly discernable in results of centrifuge tests, allowing for comparison to settlement predictions. Results are discussed in light of typical compaction specifications, oedometer-based predictions, and implications for the design of compacted embankments.
Shear Strength of Large-Size Shredded Scrap Tires
Authors: Graham Megan A. , Kjartanson Bruce H. , Lohnes Robert A.
Published: April 2007

One application for recycling large (1.4-m top size) shredded tires is as an intermittent stream or ravine crossing in place of a culvert. To measure the shear strength of large-size shredded scrap tires for use in slope stability analyses, a large-scale direct shear box (0.91 0.91 m in plan) was constructed. Two failure criteria were used, yielding similar results. A friction angle of 37° and a cohesion intercept of 3.1 kPa were obtained for large shear displacements, and the same friction angle of 37° and a zero cohesion intercept were interpreted using the 10 percent displacement failure criterion as defined by AASHTO. When shear-strength data on shredded tires from this and previous studies are analyzed, there is no apparent relationship between shred size and strength. The shear strength of the combined data, however, are well represented by the power function τ = 1.68σ0.74, where both τ and σ are in kPa. It is suggested that this nonlinear relationship, independent of shred size, can be used in stability analyses where the shear strength of shredded tires is needed.
Evaluation of Chemical Modifiers and Stabilizers for Chemically Active Soils—Clays
Authors: Petry Thomas M. , Das Braja
Published: April 2007

Of the types of soils that occur in nature, clay soils are the most physicochemically active. Their natural tendencies to change volume with moisture level changes cause billions of dollars of damage annually to transportation facilities. Methodologies to modify and stabilize their damaging behavior have been widely sought. In fact, there is evidence of clay soil stabilization in antiquity. Because these problematic soils are chemically active and their behavior can be improved through the application of chemical agents, a multitude of these agents have been applied. Some of these agents are naturally occurring, some are derived by manufacture, and some are the waste products of manufacturing processes. Why these clays are chemically active, how agents can be applied to improve the behavior of clays, and why the agents proposed should be evaluated are reviewed. Minimum requirements for adequate testing and evaluation are provided.
Safety of Motorway Lighting
Authors: Bruneau Jean-François , Morin Denis , Pouliot Marcel
Published: April 2007

The safety aspects of motorway lighting and its capacity to prevent nighttime accidents are examined. The analysis is based on a night/day accident rate ratio method to compare the safety benefits of two alternatives to dark motorways: continuous lighting and interchange lighting alone. Various sources of data are used to calculate night/day accident rate ratios, such as traffic volume records, accident databases, and field surveys. Three categories of accidents have been used: fatal and injury accidents, property damage only, and all accidents. The results are similar to those from recent literature. Continuous lighting reduces the overall accident rate by 33 percent ( p < .001) in comparison with interchange lighting alone and by 49 percent ( p < .05) compared with dark motorways. Furthermore, a breakdown by categories of average daily traffic for these comparisons reveals that accident reductions are still valid regardless of traffic flow.
Why Will Some Individuals Pay for Travel Information When It Can Be Free? Analysis of a Bay Area Traveler Survey
Authors: Wolinetz Louis D. , Khattak Asad J. , Yim Youngbin
Published: April 2007

Substantial government resources are invested in the provision of dynamic travel information. This information may help travelers make better decisions, which can reduce traffic congestion and pollution. A survey of 1,000 San Francisco Bay Area residents was conducted in 1998 as part of the TravInfo field test, and the stated preference questions were analyzed. Respondents were asked whether they sought travel information and, if so, whether they were willing to pay for a hypothetical advanced traveler information system (ATIS) that provided automatic notification of unexpected congestion on their usual travel routes, estimated time of delay from unexpected congestion on their usual routes, automatic alternate route planning around congestion, and estimated travel time on their usual route and on any planned alternate routes. Overall, willingness to pay for an ATIS was higher than expected from the literature. Sixty-six percent of the respondents sought travel information, and, of these information seekers, 71 percent were willing to pay for an ATIS (average $3.84 per month, or $0.74 per call). Statistical analysis involved estimating binary and ordered probit models with and without sample selectivity. Propensity for seeking travel information was significantly related to respondents who were female, employed, took longer trips, faced unexpected congestion, and owned a cellular telephone. Increased willingness to pay for an ATIS was related to respondents who were young and male, altered trips in response to information, and stated a greater desirability for the hypothetical ATIS. Findings suggest that a market may exist for high-quality dynamic travel information.
Effects of Conformal and Nonconformal Vision Enhancement Systems on Older-Driver Performance
Authors: Caird J.K. , Horrey W.J. , Edwards C.J.
Published: April 2007

The effects of two types of vision enhancement system (VES) displays on younger- and older-driver performance were systematically examined in various contexts. Younger and older drivers used either a conformal or a nonconformal VES display while driving in a fixed-base driving simulator. Within each block of trials, traffic scenarios were used to test driver performance: everyday driving, intersection approaches, emergency events, and VES failure. Conformal imagery directly highlighted aspects of the traffic environment, whereas nonconformal displays were coupled to environmental events but not superimposed on them. In all driving scenarios, conformal displays had a performance advantage over nonconformal displays. These advantages, however, depended on what was highlighted and whether a highlight covered or obscured important information about the environment. The perceived benefits of VESs are in situations where visibility is limited by weather (e.g., fog, snow, or rain), time of day (e.g., night or dusk), or roadway geometry (e.g., curves or railway crossings). Implications of the results for the design of conformal and nonconformal VESs and for future research are discussed.
Bus Timetables with Even Passenger Loads as Opposed to Even Headways
Authors: Ceder Avishai
Published: April 2007

Bus timetables with even headways often require passengers to adjust to given timetables instead of adjusting the timetables to fluctuating passenger demand. This expectation is a main source of unreliable service that extends passenger waiting times at bus stops and creates overcrowding. Alternative transit timetables are created to improve the correspondence of vehicle departure times with passenger demand while minimizing resources (number of buses required). An automated method is presented. With the growing problems of transit reliability, and the advance in the technology of passenger information systems, even and clock headways become less important. Therefore, more efficient schedules from both the passenger and operator perspectives can be realized. The method presented uses an informative graphic technique. This approach enables the scheduler to examine changes in bus departure times and to obtain immediate feedback on the expected average passenger loads.
Evaluation of Feeder Bus Systems with Probabilistic Time-Varying Demands and Nonadditive Time Costs
Authors: Chien Steven I. , Spasovic Lazar N. , Elefsiniotis Spyridon S. , Chhonkar Renu S.
Published: April 2007

Optimal fixed-route conventional bus (CBS) and flexible-route subscription bus (SBS) systems are compared. The average cost, including operator and user costs, is defined as the objective function to be minimized. The decision variables are route spacing and vehicle size in CBS, but service area and vehicle size in SBS. The systems serve probabilistic demand that varies over a 10-h operating period with high demand in the morning and afternoon peak hours. Passengers are assumed to have nonadditive value of time. Average cost per trip is calculated for a numerical example designed to compare the suitability of a particular service under various demand conditions. For this particular example, the CBS provides the lower-cost service. However, the operator can further reduce the cost of daily operation by providing the CBS service in periods of high demand and operating the SBS during off-peak periods. In general, the threshold value of demand at which one system is more cost-effective than another is readily calculated. A sensitivity analysis is conducted to show the effect of varying model parameters on the objective functions and the decision variables.
How Effective Is Computer-Assisted Scheduling and Dispatching in Paratransit? Results from a Survey
Authors: Pagano Anthony M. , Metaxatos Paul , King Mark
Published: April 2007

Although numerous computer-assisted scheduling and dispatching (CASD) systems have been implemented, few implementation processes have been observed and methodically described. Relevant experience is documented through a survey of paratransit operators across the United States, providing insights into the processes used, problems encountered, and benefits and costs experienced in implementing CASD systems. One-half of paratransit operators do not use the major features of their new CASD system. Operators have noted gains in efficiency, effectiveness, and quality, with some reporting significant changes, but on the whole, pre- and postimplementation comparisons do not show the kind of dramatic efficiency changes for which operators have hoped. Moreover, training efforts are likely to become a lightning rod for discontent as the staff makes a transition to the new system, and management should make every effort to ensure that funding and time are allocated for training as early as possible. Also, the implementation budget should include funds for the development of custom reports and separate, focused training for management. Further, operators strongly favor adding a dedicated project manager to the CASD system implementation process. Finally, both policy and personnel issues limit full implementation of CASD systems. As long as agencies restrict use of their vehicles to certain groups of passengers, optimization algorithms cannot reduce vehicle usage. And as long as training and attitudes do not match needs, personnel problems will persist.
Winston-Salem Mobility Manager: Data Collection, Validation, and Performance Evaluation
Authors: Stone John R. , Baugh John W. , Chakravarty Shoma , Surasky Michael N.
Published: April 2007

The Winston-Salem Mobility Manager project has served as a test bed for advanced public transportation systems technology since 1995. The aspects of remote data collection, validation, and performance evaluation are discussed. The computerized scheduling software for Trans-AID, the local paratransit system, was accessed and passenger RIDE files were downloaded. Java-based utilities and conventional spreadsheets removed invalid data, sorted urban and rural passenger trips, and compared transit productivity measures. Validated Trans-AID data show relatively few data entry errors, some logical errors, and high time-window violations. Ridership, productivity, and service gains determined by intuitive assessment of traditional measures are not supported by statistical analysis. Rather, the results of t-tests suggest counterintuitive management actions to improve service and productivity. Internet-based methods of data collection, validation, and evaluation demonstrate promise for real-time transit management and agency monitoring.
Feasibility, Financial, and Environmental Analysis of an Advanced Maglev-Based Intermodal System
Authors: Steingröver Andreas , Krevet Rasmus , Bertini Robert L.
Published: April 2007

The magnetically levitated (maglev) intermodal system named Auto-shuttle is a new transportation concept that can be built along existing major transportation arteries such as freeways. The technical feasibility, financial aspects of a sample application, and key environmental features of this system are examined. Compared to automated vehicles driving autonomously, Autoshuttle demonstrates substantially higher degrees of safety, environmental friendliness, and economy.
Using Pavement Distress Data to Assess Impact of Construction on Pavement Performance
Authors: Chang Chieh-Min , Baladi Gilbert Y. , Wolff Thomas F.
Published: April 2007

Most state highway agencies specify incentives, disincentives, or acceptance criteria based on one or more attributes that can be measured during or immediately after construction (smoothness, early completion of construction, and nuclear density). In many scenarios in which contractors were awarded incentives, the pavement showed premature distress after construction. Furthermore, the magnitude of the incentive or disincentive is typically determined on the basis of intuition and past practice, without assessing the effect of the incentive’s attribute on pavement performance. In a study sponsored by the Michigan Department of Transportation (MDOT) and conducted by the Pavement Research Center of Excellence at Michigan State University, the impact of segregation on pavement performance was assessed, and an expedient test to detect segregation was developed so that MDOT could establish incentives, disincentives, or acceptance criteria. The study included 17 segregated pavement projects and 2 nonsegregated projects. Two types of segregation-related distress were observed: raveling, which was observed on 11 projects, and cracking, which was observed on 7 projects. Three projects showed both raveling and cracking. For each project, the raveled areas and the length of the cracks were measured over time, and their rates of growth were assessed. On the basis of the results, the reductions in the pavement service life due to raveling and cracking were estimated. It is shown that areas with heavy and medium degrees of segregation experience on average 73 and 56 percent reduction in pavement service life, respectively, due to raveling and 46 percent due to segregation-related cracks.
Developing Critical Field Permeability and Pavement Density Values for Coarse-Graded Superpave Pavements
Authors: Cooley L. , Brown E. Ray , Maghsoodloo Saeed
Published: April 2007

Within the hot-mix asphalt (HMA) community, it is generally accepted that the proper compaction of HMA is vital for a stable and durable pavement. Low in-place air voids have been shown to lead to rutting and shoving, whereas high in-place air voids have been shown to reduce a pavement’s durability through moisture damage and excessive oxidation of the asphalt binder. Recent research has suggested that coarse-graded Superpave-designed mixes are more permeable than conventionally designed pavements at a given air void content. This higher permeability can lead to durability problems. The pavement density at which coarse-graded Superpave mixes become permeable was evaluated by using a field permeability device. On the basis of the data collected, 9.5- and 12.5-mm nominal maximum aggregate size (NMAS) mixtures become excessively permeable at approximately 7.7 percent in-place air voids, which corresponded to a field permeability value of 100 × 10−5 cm/s. Mixtures having a 19.0-mm NMAS became permeable at 5.5 percent in-place air voids, which provided a field permeability value of 120 × 10−5 cm/s. Coarse-graded mixes having an NMAS of 25.0 mm became permeable at 4.4 percent air voids, which corresponded to a field permeability value of 150 • 10−5 cm/s.
Presignals: Current Applications and Issues
Authors: Ogden Brent D.
Published: April 2007

Applications and technical issues related to using presignals to improve the safety of at-grade light rail transit crossings are discussed. A presignal installation has roadway traffic signal heads placed ahead of a downstream, signalized frontage roadway intersection and the stop bar displaced in advance of the grade crossing. This signal ensures that a vehicle stops at a red traffic light before the grade crossing area and the clear-storage zone between the grade crossing and downstream intersection. Presignals have been used for many years and are a state standard in Michigan and South Carolina. However, a tragic accident in which a school bus was hit by a METRA commuter train in Fox River Grove, Illinois, brought renewed attention to this treatment. The state of Illinois installed a presignal at the Fox River Grove grade crossing and has developed a statewide policy for the use of presignals elsewhere. Background is provided on presignals, including alternative types of queue control using traffic signals. The key design features of a presignal installation are highlighted. Outstanding technical issues are identified, including future research to refine policies or warrants for presignals and applicable design standards.
"Quiet" Automated People Mover Operation in Indonesia: First Decade
Authors: Rogers Lee H.
Published: April 2007

After four decades of uninspired automated people mover (APM) evolution in the United States, the urban public has not widely accepted this technology. This attitude mainly reflects the results of technically successful projects that have failed with regard to financial viability, traffic patronage, urban planning, and social merit. A modest firm in Brazil has developed and tested a new technology. In 1988, a private group of Indonesian investors used the Aeromovel technology to retrofit a cultural complex with an APM loop distributor. From 1989 to 1999, this pneumatically propelled loop handled 3.5 million revenue passengers and generated only 250,000 vehicle-km. Aeromovel has shown that private equity can be obtained with capital costs below $20 million per 1.61 km. The effectiveness is derived from the speed of installation, low cost of daily operations and maintenance, and frequent service.
Some Characteristics of Foamed Bitumen Mixes
Authors: Nataatmadja Andreas
Published: April 2007

A study was conducted at the School of Engineering of Griffith University on characterization of a range of foamed bitumen stabilized mixes in the laboratory. Marshall and servo-controlled gyratory compactors were used in specimen preparation. A closed-loop, servo-controlled dynamic loading system was utilized to determine the resilient modulus. It was found that the Marshall compaction method produced higher resilient modulus values compared with the gyratory compaction method. Moreover, Marshall compaction showed an optimum bitumen content associated with the maximum density. The gyratory compactor produced specimens that were less dependent on bitumen content but had higher density values. The temperature used to cure the specimens was also examined. An accelerated curing temperature of 60°C was found to be too high, resulting in an over-estimation of the resilient modulus compared with specimens cured at an ambient temperature. Furthermore, the resilience test results also showed that the resilient modulus was significantly affected by the applied strain; with higher strain, a lower modulus resulted. Because of its relatively low bitumen content and use of lime additive, the resilient modulus of foamed bitumen mixes is affected by temperature variation less than that of typical hot-mix asphalt concrete mixes.
New Activity Diary Format: Design and Limited Empirical Evidence
Authors: Arentze Theo , Dijst Martin , Dugundji Elenna , Joh Chang-Hyeon , Kapoen Loek , Krygsman Stephan , Maat Kees , Timmermans Harry
Published: April 2007

The results of a project conducted to compare and evaluate a new activity diary design with two more-traditional diary formats are discussed. The project was conducted as part of a research program involving several research groups in the Netherlands. The design of a stage-based diary, a day-planner format, and a new format representing a combination of the stage-based and day-planner formats is reported. Some small-scale qualitative and quantitative analyses were carried out on the basis of a pilot survey. The three formats were evaluated on their trip-reporting rates, rounding of time, missing activities, and overlapping begin and end times. Respondents were asked about their experiences with reporting trips and activities and their overall impressions of the formats. The advantages and disadvantages of each alternative format are discussed, and some conclusions about design criteria are drawn.
Prompted Recall in Global Positioning System Survey: Proof-of-Concept Study
Authors: Bachu Prashanth K. , Dudala Trisha , Kothuri Sirisha M.
Published: April 2007

Modeling procedures in transportation planning depend on the quality of data collected from personal travel surveys, which in turn depend on the data-collection technique. All conventional data-collection techniques rely on respondents to report the time, distance, and location attributes of a trip, among other things. Respondents rarely know addresses that they visit with sufficient detail to permit accurate geocoding. Also, it has been observed that short trips are underreported. Earlier studies proved the feasibility of using the Global Positioning System (GPS) as an alternative to acquire error-free, high-quality information on trip-making behavior. However, all GPS survey methodologies tested relied on the respondent to enter information into a personal data assistant (PDA) as the trip is being made and to intervene in other ways to record all data for each trip. This adds the expense of a PDA and its power supply and puts a burden on the respondent. A method that uses GPS technology with less complexity, involving less cost and minimal user intervention while making the trip, is tested and explained. Additional trip attributes that cannot be recorded by the GPS receiver were obtained after the survey period by prompted recall, in which the respondents were aided with maps displaying their travel paths. Analysis of the data showed that this method performed very well. However, a still-larger survey is needed to estimate the benefits.
Data-Mining Tools for the Support of Signal-Timing Plan Development
Authors: Smith Brian L. , Scherer William T. , Hauser Trisha A.
Published: April 2007

Intelligent transportation systems (ITS) include large numbers of sensors that collect enormous quantities of traffic-flow data. The data provided by ITS are necessary for advanced forms of control. However, more basic forms of control, such as time-of-day (TOD) signal-timing plans that are widely used in the United States, do not directly rely on the data. Thus, sensor data often are unused and discarded. The sensor data, however, can provide large amounts of information that can aid in the development of improved TOD signal-timing plans. Data-mining tools are necessary to extract information from the data necessary to improve timing-plan development and to allow the timing-plan development and monitoring processes to be automated. A research effort that investigates the application of data-mining tools, including statistical clustering and classification techniques, to aid in the development of traffic-signal-timing plans is described. A case study was conducted that illustrated that hierarchical cluster analysis can be used to identify temporal interval breakpoints that support the design of a TOD signal-control system. The cluster analysis approach was able to use a high-resolution system state definition that takes full advantage of the extensive set of sensors deployed in a traffic signal system. Finally, the case study also demonstrated that a classification and regression tree could be developed that can be used to monitor automatically the quality of TOD intervals as traffic conditions change. The results of this research indicate that advanced data-mining techniques have great potential to provide automated techniques that assist traffic engineers in signal-control-system design and operations.
Using Intelligent Transportation Systems Travel-Time Data for Multimodal Analyses and System Monitoring
Authors: Eisele William L. , Rilett Laurence R. , Brown Mhoon Kendra , Spiegelman Clifford
Published: April 2007

Intelligent transportation systems (ITS) technologies and infrastructure are a potentially rich travel-time data source for travel-time mean and variance estimates. ITS data traditionally have been deployed and used in real time for passenger cars. How ITS data can be used for multimodal analyses and system monitoring is examined. The methodology used is applicable to any detector technology. Automatic vehicle identification (AVI) data were collected along a 3.2-km (2-mi) segment of US-290 in Houston, Texas. Simultaneous instrumented test vehicles collected travel-time data, and commercial-vehicle travel-time data were collected by video. The nonparametric loess statistical procedure was used to estimate the travel-time distribution properties as a function of time of day. The first application presented investigates how well link travel times from AVI replicate travel conditions for commercial vehicles. During congested conditions, average differences in travel-time estimates of 6.4 percent were found, whereas percent differences in coefficient of variation (reliability) were 14.7 percent. The research concludes that it may be reasonable to provide real-time traffic maps specifically for commercial vehicles. The second application investigates the accuracy of the AVI data for system monitoring. Estimated mean differences between AVI data and test vehicles were small (0.8 percent), whereas the ratio of the mean to the standard deviation (coefficient of variation) was relatively high (37.6 percent) during congested conditions. The AVI data source is found to provide a very cost-effective data collection method with which to estimate mean travel time while increasing confidence in the estimate.
Integrated Networking and Visualization Approach to Crash Data Analysis
Authors: Yi Ping , Xiao Yingcai , Devarakonda Saroja
Published: April 2007

An integrated networking and visualization approach to crash data analysis is proposed and tested. A three-tier client server networking system is set up to serve as the backbone framework for data communication between the central database and distributed users. By using a local database-management system, a user at the client level can view the crash data through data mapping and attribute listing and can analyze the data through nested query and sorting operations. A visualization module, based on the types, movement characteristics, and points of impact of the vehicles involved in the crash, automatically constructs the collision diagram by using data selected for visual display. Data on both intersections and pipeline sections can be visualized and analyzed. The model was tested by using crash data obtained from the Ohio Department of Public Safety, and examples are presented. It was discovered that the proposed approach to crash data analysis not only is very effective but also is more accurate and time efficient than the conventional data-analysis approach.
Geographic Information System—Based Integrated Model for Analysis and Prediction of Road Accidents
Authors: Saccomanno F. Frank , Fu Liping , Roy Rajeev K.
Published: April 2007

The applicability and reliability of accident analysis and prediction models depend on their ability to integrate relevant input from disparate databases in a seamless and automated manner. These inputs include information on road geometry, traffic composition, accident profiles, and spatial referencing. With powerful functionality in spatial referencing, data management, and visualization, geographic information systems (GISs) provide a natural platform for this type of model. An integrated and user-friendly GIS platform for road accident analysis and prediction is described. To demonstrate this platform, it has been applied to safety problems specified at different levels of spatial aggregation, from individual route sections to the overall network. The model was developed by using databases obtained from the Ontario Ministry of Transportation.