bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil Suction Dispersion and Statistical Analysis with Depth at the Medford Airport
Authors: Nevels James B.
Published: April 2007

The use of soil suction measurements has steadily increased in geotechnical practice. A current standard test procedure that describes the use of laboratory filter papers as passive sensors to measure the soil matric and total suction is ASTM D5298-94. The principal objective of the research presented here was to evaluate dispersion of suction measurements with depth using the filter paper method described in the ASTM standard. In a single test boring to a depth of 5.33 m, 35 samples were taken at intervals of 152.4 mm. Each sample was separated into four replicate samples. The matric and total suction of each of the 35 sample intervals were then measured, resulting in a total of 278 suction measurements. To manage this volume of tests, the sample size was split approximately in half, and each portion was separately tested. This approach led to severall insights into the test procedure, such as the effect of delay in transferring the filter paper from the specimen container into the metal container. Sampling and testing are described. The dispersion of both the total and the matric suction measurements was characterized in three ways: the range of measurements in each sample interval, the standard deviation of measurements in each sample interval, and an error function defined as the difference between each measurement and the mean for the sample interval. Each of these statistics was plotted as a histogram. A chi-squared test was applied to measure the goodness-of-fit of a t-distribution fitted to the error as defined by the difference between each measurement and the mean for that sample interval. Results indicate precision for total and matric suction measurements of 0.0540 log kPa within one standard deviation. Analysis does not indicate a substantial difference between the error associated with total suction measurements and that associated with matric suction measurements. A brief description of the conventional geotechnical site characterization is presented for the Medford Airport.
Suction Measurements on a Saskatchewan Soil Using a Direct-Measurement, High-Range Suction Sensor
Authors: Fredlund Delwyn G. , Gan Julian K-M. , Guan Yun , Richardson Neil
Published: April 2007

A tensiometric-type suction sensor capable of direct measurement of matric suctions greater than 100 kPa has recently been developed. The sensor has been used to measure matric suctions up to 1250 kPa. The sensor makes use of the tensile strength of water for the measurement of matric suction. The cavitation of water in conventional tensiometers occurs at a negative pressure approaching 1 atmosphere because of the presence of cavitation nuclei. In the absence of cavitation nuclei, the tensile strength of water can be on the order of several atmospheres. The direct-measurement, high-range suction sensor has been used for the measurement of matric suction on borehole samples obtained during a soils investigation at a bridge site near the town of Outlook, Saskatchewan, Canada. The method has proven to be fast and simple to use. Matric suction measurements of the samples from the Outlook bridge site are presented, along with an interpretation of the laboratory data.
Characteristics and Performance of Prefabricated Vertical Drains for Enhanced Soil Flushing
Authors: Quaranta J. D. , Gabr M. A. , Szabo D. , Bowders J. J.
Published: April 2007

The use of prefabricated vertical drains (PVDs) under vacuum conditions for soil flushing was investigated with soils consisting of 100 percent sand or a combination of 80 percent sand and 20 percent kaolinite. Tests of the 100 percent sand specimens indicated that the areal extent of the PVD zone of influence remained approximately 16 to 21 times the PVD-equivalent diameter (PVD circumference/π) as the extraction vacuum increased from 2.5 to 20 kPa. Tests of the sand kaolinite specimens (80/20 soil) indicated that the areal extent of the PVD zone of influence remained approximately 5 to 8 times the PVD equivalent diameter as the extraction vacuum increased from 2.5 to 20 kPa. The effective zone of influence in the 80/20 soil did not show a corresponding increase in areal extent as the vacuum pressure was increased beyond the PVD embedment depth. Pilot-scale tracer flushing tests demonstrated the feasibility of using PVDs for flushing 100 percent sand soil. The tracer testing demonstrated that longer flushing times were necessary to achieve 80 percent cleanup levels as the dry unit weights of soil increased from 1.57 to 1.67 g/cm3. The ratio of final to initial concentration reached 0.2 after flushing of the 1.57 g/cm3 soil for approximately 40 minutes. A similar ratio was reached after flushing of the 1.67 g/cm3 soil for 50 minutes.
Relationship Between Pavement Performance and Routine Maintenance: Mixed Logit Approach
Authors: Mohamad Dadang , Sinha Kumares C. , McCarthy Patrick S.
Published: April 2007

A mixed logit approach was used to investigate the relationship between routine maintenance and pavement performance. A discrete model was developed to examine how pavement performance levels affect the probability of performing maintenance on pavement sections. Another continuous model was formulated to investigate the effect of maintenance on the level of pavement performance. Maintenance was considered a discrete event representing a binary choice of its being performed on a pavement section or not. Pavement performance levels were represented by roughness numbers. Other variables included were pavement thickness, pavement loading, and a regional factor. Pavement thickness was assumed to represent initial construction, and traffic loadings were in the form of equivalent single-axle loads. The regional factor represented the weather and climatic differences between the northern and southern regions. A two-stage procedure was applied to evaluate the mixed logit approach. The data from the Interstate highways in Indiana for 1984 to 1985 were used for model estimation. The mixed logit approach produced much better results than the single-equation method in specifying the models in terms of coefficient signs and their significances. The results confirmed that pavement roughness was affected by maintenance and that the decision to undertake maintenance was influenced by the expected level of pavement roughness.
Methodology to Estimate User Costs in Indiana Bridge Management System
Authors: Son Youngtae , Sinha Kumares C.
Published: April 2007

A methodology to estimate user costs developed for incorporation in the Indiana Bridge Management System is presented. The methodology estimates user costs not only for detouring vehicles, but also for vehicles traveling through bridges with narrow deck widths or with partial lane closures, causing additional travel-time cost resulting from speed reduction by capacity constraints. An example of user cost computation for bridges in Indiana is provided.
Pilot Applications of Electrochemical Chloride Extraction on Concrete Bridge Decks in Virginia
Authors: Clemeña Gerardo G. , Jackson Donald R.
Published: April 2007

A new method for rehabilitating salt-contaminated concrete bridge elements, electrochemical chloride extraction (ECE), was applied on two deck spans in Virginia as part of a pilot study. This treatment, performed on half of the deck at a time, involved placing a temporary electrolyteanode system (inert catalyzed titanium mesh sandwiched between two layers of synthetic felt) on the surface of the deck and applying charges ranging from 741 to 1,077 A-hr/m2 between the anode and the rebars for 57 to 58 days. Approximately 72.2 to 82.1 percent of the chloride ions were removed from the concrete. A minor difficulty was encountered in controlling the pH of the electrolyte during the first several weeks of the treatment. Lithium ions, which were present in the electrolyte for two portions of the deck, migrated readily into the concrete. An attempt to simultaneously inject the corrosion inhibitor (C6H5)4P+ in the concrete in the presence of Li+ yielded uncertain results. Overall, this pilot project successfully demonstrated that an effective ECE treatment is simple to perform on a full-size concrete deck.
Employee Trip Reduction Without Government Mandates: Cost and Effectiveness Estimates from Chicago
Authors: Pagano Anthony M. , Verdin JoAnn
Published: April 2007

Employee trip reduction demonstration projects were organized by the Chicago Area Transportation Study, the metropolitan planning organization in the Chicago area. This paper is based on an independent evaluation of the demonstration projects. The primary source of data for this evaluation was a series of interviews conducted with program administrators and employee trip coordinators at each organization that participated in the demonstration. Voluntary costs, which are costs incurred to implement an employee trip reduction program without the necessity to comply with government regulation, are estimated. The average demonstration organization was able to reduce solo driving rates by 5.5 percentage points. This reduction was attained at an average annual voluntary cost per employee of $34.38. The average voluntary cost per car removed for organizations that actually reduced the solo driving rate was $473. Each $10 expenditure per employee is associated with a 1 percent reduction in the solo driving rate. Every $ 10 increase in annual incentive costs per employee was found to be associated with a 1.3 percent decrease in the solo driving rate. It also was found that elimination of government mandates has reduced the cost of implementing an employee trip reduction program by one-half. Tax incentives should be established to encourage organizations to begin voluntary programs. Such a tax-incentive scheme, combined with an aggressive education program, may be able to achieve substantial reductions in pollution and congestion in urban areas.
Assessing Visitor Responses to Iowa Scenic Byways Pilot Program
Authors: Dahlquist David L. , Peterson Karen
Published: April 2007

Iowa's Scenic Byway Program was initiated by the Iowa Legislature in 1987. The Iowa Department of Transportation chose four pilot routes in Iowa and worked with local governments to develop agreements for erecting and maintaining signs on the scenic byways. The Iowa Department of Economic Development's (IDED) Division of Tourism initiated an advertising program for the pilot phase by selecting unique names for each scenic byway, printing and distributing colorful brochures at 18 Iowa Welcome Centers, and placing advertisements in Midwest regional newspapers. Davidson-Peterson Associates, Inc. (DPA), and David L. Dahlquist Associates, Inc. (DDA), were commissioned by IDED to evaluate visitors' responses to Iowa's new scenic byways pilot program during the 1994 tourism season. The research objectives were to: ( a) measure the economic benefits that have accrued to participating counties and communities from the pilot program; ( b) determine how travelers have responded to this program and how their travel behavior has been influenced by this program; and ( c) assess the interest of travelers in Iowa in the scenic by ways program and thereby to project future benefits that might be derived from continuing and expanding this program. To meet the research objectives, DPA and DDA conducted 600 telephone interviews, collected 456 on-site, self-administered questionnaires, and conducted 70 in-depth interviews. The pilot program had some successes in a short time. There were economic benefits, and visitors were pleased with their experiences. Visitors and local officials made suggestions for improvements in signage, additional information in the brochures, and changes in the byway routes.
Digital Photogrammetric Techniques for Transportation Data Acquisition and Management
Authors: Agouris Peggy , Stefanidis Anthony , Beard Kate
Published: April 2007

State-of-the-art digital photogrammetric techniques for the acquisition of transportation-related information from digital are presented. Photogrammetric data collection can be performed using either aerial or closerange sensors. The difference between the two lies on the nature of data that can be acquired, in direct analogy to the resolution differences. The current state of technology for digital imagery acquisition permits the direct capture of digital close-range imagery, whereas digital aerial imagery is produced by digitizing analog diapositives. Thus, the availability of metric quality imagery in digital format is ensured, either directly or indirectly. Advancements in digital photogrammetric research are making feasible the transition from analytical to digital photogrammetric methods in transportation applications. This transition is characterized by automation and improved performance of traditional tasks. Furthermore, the use of imagery in digital format is offering the potential to radically modify tasks, products, and procedures. Digital photogrammetric techniques can be embedded within a transportation data-management environment, supported by additional information, and supporting decision making.
Airport Ground Access and Intermodal Interface
Authors: Gosling Geoffrey D.
Published: April 2007

The airport ground transportation system is receiving increasing attention from airport authorities and regional transportation planning agencies. The need to plan for facilities at the airport and concern about the impact of traffic on streets and highways surrounding the airport, and about emissions generated by this traffic are forcing airports to consider strategies to reduce or mitigate ground access traffic. The 1991 Intermodal Surface Transportation Efficiency Act has caused transportation agencies at all levels to address the integration of different transportation modes, including coordination between the air and surface components of the transportation system. The range of ground access planning issues is reviewed, and three alternative strategies to improve intermodal connections at airports are discussed: new or upgraded rail links, off-airport terminals, and ground transportation centers at the airport. The planning and design issues that arise with each type of facility are addressed, as well as the analytical tools and data needed to evaluate the wide range of airport ground access projects and to plan the implementation of those selected. These include air passenger and truck surveys, development of operational data on the ground access system, and use of access mode choice and traffic flow models. Research needs in the area of airport ground access are also discussed.
Relationship Between Particle Size Distribution and Specific Surface Area of Urban Roadway Stormwater Solids
Authors: Sansalone John J. , Buchberger Steven G. , Koran Joseph M. , Smithson Joseph A.
Published: April 2007

Surface area is a primary factor in determining many physical and chemical properties of solids, especially particles. In urban and highway runoff, solids can mediate the partitioning between the dissolved and particulate-bound phases of metal elements and organic compounds. Solids are also capable of adversely affecting roadway drainage appurtenances through sedimentation and clogging. Solids characteristics of primary importance for both solute adsorption and clogging and sedimentation are particle size distributions (PSDs), specific surface areas (SSAs), and mass loadings. PSD and SSA results are presented for rainfall and snowmelt solids from a heavily traveled urban roadway in Cincinnati. Integration of the PSD and SSA results indicates that particle surface area is greatest for the midrange (> 100 μm) to the coarser end (<2000 μm) of the gradation. SSA results determined using the assumption of smooth spherical particles are indicated to grossly underestimate actual SSA values.
Development of a Statewide Truck-Travel Demand Model with Limited Origin-Destination Survey Data
Authors: Park Man-Bae , Smith Robert L.
Published: April 2007

A simple statewide truck-travel demand model for Wisconsin was developed using only readily available data, including a small amount of data from origin-destination travel surveys (O-D) and fairly extensive truck-classification count data. A simple trip-rate trip-generation model based on zonal population was used to estimate the initial internal trip productions and attractions. Despite the small amount of O-D survey data that were available, gravity-model friction-factor curves were developed for three trip types. The calibrated gravity models produced trip tables that were good matches for the O-D survey data. The calibrated gravity models were then used as the modeling framework for the adjustment of zonal productions and attractions by selected-link-based (SELINK) analysis. SELINK adjustment factors were computed for all zones with trips on one or more of the selected links. The adjustments were made so that the ratio of the actual volume for the selected link (ground count) to the total assigned volume approached 1 for all selected links. The SELINK analysis produced a calibrated model after only three iterations when either 16 or 32 selected links were used statewide for the calibration. The overall accuracy of the calibrated model was measured by using classification count data for 154 locations around the state. The model provided a good fit based on a wide variety of measures, including percent root-mean-square error and comparisons for screenlines, functional class, areas, and vehicle kilometers traveled.
Minimax Population Exposure in Routing Highway Shipments of Hazardous Materials
Authors: Erkut Erhan , Glickman Theodore
Published: April 2007

A routing model for hazardous materials with two objectives—to minimize maximum population exposure and to minimize total travel time—is introduced. The population exposure is quantified by the number of people in an impact circle of a selected radius. To solve this two-objective problem, the focus is placed on the second objective, with a constraint on the first objective. This results in a problem that is easy to solve and has a solution that is easy to interpret. To demonstrate the use of this model, a case of nuclear waste shipments (i.e., spent fuel) in the United States in considered. The model is applied, with two bounds on high-level population exposure, to 10 nuclear waste origins. The results of this application are reported. The model behaves in a predictable (and desirable) way, avoiding major population centers via detours. With its ability to quantify trade-offs between competing objectives, and its capacity to generate multiple routes for a shipment, the model has the potential to serve in a decision-support role for planning hazardous materials routes.
Signing and Pavement Marking for Concurrent-Flow High-Occupancy-Vehicle Lanes: Summary of Current Practice
Authors: Fendrick Michael J.
Published: April 2007

Concurrent-flow lanes account for more than half of existing high-occupancy-vehicle (HOV) mileage in the United States. Traffic on this type of HOV lane operates in the same direction as the adjacent traffic, typically in the far-left lane. Limited national guidance for signing or pavement marking is available that specifically addresses concurrent-flow HOV lanes. Therefore, the 13 states now using this type of lane have independently developed their own designs and standards. As a result, different signing and marking practices are being applied throughout the nation. Some of the signing and marking treatments being used on concurrent-flow HOV lanes in several states are documented. A summary of the current state of the practice on several signing and marking issues is included, on the basis of reviews of available design guides and project plans. The current standard practice is investigated, and the input of designers and state personnel is examined to determine the reasoning behind specific signing and marking treatments. General conclusions include the need for more specific direction on signing and marking practices to encourage uniformity. This step is desirable as more states begin to implement HOV-lane strategies to deal with urban congestion. The standards should be based on a merging of current practices and should be incorporated as a new section of an updated Manual on Uniform Traffic Control Devices. In addition, recommendations for specific design elements are presented.
Evaluation of New Jersey Route 18 OPAC/MIST Traffic-Control System
Authors: Andrews Christina M. , Elahi S. Manzur , Clark James E.
Published: April 2007

Conventional traffic-control strategies have limitations in handling unanticipated traffic demands. An adaptive traffic-signal control is expected to mitigate this problem and improve overall system performance. Furthermore, with the increasing needs of evolving intelligent transportation systems, traffic signals are expected to provide significantly greater functionalities, which can be achieved only by adaptive control. A product of many years of development, Optimized Policies for Adaptive Control (OPAC) represents a significant step forward in adaptive signal-control research. The OPAC strategy was field-tested at a New Jersey site. The performance of OPAC was compared against a well-designed time-of-day signal control. The evaluation was performed under various traffic-demand conditions and included both isolated intersections and arterial sections. The analysis indicated a highly significant improvement with OPAC control. OPAC showed its best performance during oversaturated conditions. It reduced the travel time and number of stops by about 26 percent and 55 percent, respectively, for the entire arterial section. OPAC also improved traffic performance during changing demand conditions. It significantly improved the performance of an isolated intersection during undersaturated traffic conditions. OPAC reduced stopped delay on the major-street approach by 40 percent without affecting the minor-street performance.
Pedestrian Access to Transit: Model of Walk Trips and Their Design and Urban Form Determinants Around Bay Area Rapid Transit Stations
Authors: Loutzenheiser David R.
Published: April 2007

Walking links practically every trip taken, yet it has not been maximized as a primary mode of transportation, and the characteristics of walk trips are little understood. The Bay Area Rapid Transit (BART) system has been used for primary analysis of characteristics of pedestrian access to transit. A travel survey of individual riders was used to develop a disaggregate discrete choice logit model of walk access to BART stations. Characteristics with the highest probability of choosing walking over another mode are distance, availability of a car, and gender. Linear regression analysis of aggregate station area characteristics was developed; density, the number of parking spaces at the station, and income and education of the residents were identified as key factors in the decision to walk. When the logit and regression models were combined into a single model, there was a clear shift toward individual characteristics over aggregate station area characteristics that determines access-mode choice. Among physical characteristics, station areas with high levels of retail activity outside downtown areas contain the highest proportion of walk trips, followed by station areas with little or no parking.
Driver Understanding of Alternative Traffic Signs
Authors: Picha Dale L. , Gene Hawkins H. , Womack Katie N. , Rhodes Lewis R.
Published: April 2007

Traffic control devices are intended to promote safe and uniform operation of motorized and nonmotorized traffic using the roadway. Motorists rely on traffic control devices to provide information about traffic laws and regulations, to identify potential roadway hazards, and to provide information to help them find their desired destinations. However, traffic control devices serve little purpose if they are not understood by a significant proportion of the driving population. The findings and recommendations of a 5-year research study conducted by the Texas Transportation Institute to assess and improve motorist understanding of traffic control devices are presented. Phase I of the project was devoted to several evaluations of 52 devices, administered to 2,414 Texas drivers. Phase II of the project was devoted to the development and evaluation of alternative designs for 10 traffic signs identified in Phase I that exhibited potential for driver misunderstanding. The Phase II evaluations included four focus groups, an initial statewide survey of 747 Texas drivers, and a follow-up survey of 212 drivers. The results of all evaluations were analyzed to distinguish significant comprehension difficulties. Recommendations for each device were based on these results and include retaining the current standard design because of adequate comprehension levels, modifying the design or use of the device to increase comprehension levels, or conducting further research to better understand driver comprehension difficulties.
Daytime Photometric Requirements for Pedestrian Signals
Authors: Mace Douglas , Finkle Mark , Pennak Sara
Published: April 2007

Forty-eight senior citizens participated in a field study of the visibility of letters and symbols in pedestrian traffic signals. Subjects were asked to identify signal messages from distances of 18.3 m and 29.3 m, with signal voltage set at 100 percent, 75 percent, and 50 percent of full power. Incandescent, fiber-optic, and light-emitting diode commercially available pedestrian signals were tested, including 22.9-cm and 30.5-cm rectangular signal housings and two round red-amber-green signals with symbol masks. Each subject was asked to identify the signal’s location in the test stimuli array, to name the signal’s display configuration (Walk, Don’t Walk, walking person, or hand), and to assess the signal’s brightness on a five-point scale. Analyses also were conducted on the percentage of responses about “too bright” signals and subject uncertainty about the signal message. Testing was conducted only on bright sunny days but did not include the worst-case condition of direct sunlight on the signal face. The analysis of recognition, uncertainty, and “too bright” responses suggested that a signal intensity of 25 cd minimizes the frequency of both “too bright” and uncertain responses regardless of size, distance, or technology, or whether the message is symbol or text. The data further suggest that 22.9-cm incandescent signals provide sufficient visibility with less phantom effect than 30.5-cm signals.
Development of Evaluation Tools for Road-Rail Crossing Consideration for Grade Separation
Authors: Hakkert A.S. , Gitelman V.
Published: April 2007

A program for expansion of Israeli railways has resulted in increased train speeds and frequencies on the most heavily used railway lines. These are situated in highly populated regions and are characterized by a significant amount of at-grade road-rail crossings. At-grade crossings present a barrier to road traffic and the danger of train-vehicle collisions. Because the current maximum train speed is about 120 km/hr, there was no clear policy concerning the need and the priority for grade separation at crossings. Simplified tools for rapid crossing evaluation when a crossing potential for grade separation is reviewed were developed. The evaluation tools include a criterion for preliminary crossing qualification and a formula for approximate evaluation of economic losses caused by at-grade crossing functioning. The field measurements and detailed investigation of the 31 most problematic locations provided a basis for building the tools. Two main factors leading to grade separation were considered: safety problems at the crossings and road vehicle delay costs. As demonstrated, the cost of accident risk at Israeli crossings does not significantly affect their ranking for grade separation. In consequence, the crossing parameters influence vehicle delays that constitute the basis for the simplified tools for preliminary crossing evaluation in Israel.
Target Funding for Substate Transportation Investment Decisions
Authors: Zemotel Linda M. , Bloom Jon A.
Published: April 2007

Minnesota developed the concept of substate area transportation partnerships (ATPs) under the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA). The ATPs are responsible for integrating regional priority projects into a unified State Transportation Improvement Program. The ATPs work within the constraint of a target funding level that estimates federal funding expected to be available to areas within the state. Controversy has developed about the methodology used to develop the target funding formula. In 1995, the Minnesota Department of Transportation (MnDOT) formed a work team to reevaluate the target funding formula. In developing alternatives, the work team reviewed methodologies proposed by other groups and researched a wide range of possible measures that could be used. The team evaluated the pros and cons of the measures before selecting 13 measures for detailed study. Measures that were considered were grouped into the three categories of system health, system size, and contributions. The team proposed five alternative scenarios, in addition to an update of the existing scenario. The scenarios were presented to MnDOT and its external partners for review and comment. The lessons learned about the process and the measures that were most acceptable for inclusion in the formula for determining target funding are described.
Comparisons of Deterministic and Stochastic Traffic Loading Models
Authors: Tatineni Maya , Boyce David E. , Mirchandani Pitu
Published: April 2007

Stochastic route choice models have been proposed as a more realistic alternative to the simpler deterministic route choice representations in models for loading traffic onto a network. However, studies on stochastic route choice models have thus far been limited to small experimental networks. Because stochastic models are in general considered to be more realistic in their assumptions than deterministic models, it becomes pertinent to examine their implementation and the corresponding traffic loading on a network of realistic size. Such an implementation for two stochastic route choice models is examined. The results indicate that the differences among the models, at the network level, for predicted link flows and average travel times between origin and destinations are not major, and therefore, deterministic models may suffice for long-range network planning. However, stochastic models predict the usage of more links in the network, and the difference in the flows at the link level may play an important role in travel advisory and route guidance systems. Some suggestions for future research are presented.
Travel Demand Forecasting Using Microsimulation: Initial Results from Case Study in Pennsylvania
Authors: Chung Jin-Hyuk , Goulias Konstadinos G.
Published: April 2007

A new practical method for more accurately estimating traffic volumes in regional transportation networks by using demographic micro-simulation is described. The method, called MIDAS-USA-Version I (MUVI), is combined with another method, access management impact simulation, which uses a geographic information system as a support tool, and can create detailed highway networks that can be used in regional models. Initial results from a case study in Centre County, Pennsylvania, are presented. The case study compares sociodemographic characteristics and the resulting traffic volumes on the regional transportation network with observed data and indicates the efficacy of the concept and the models used. This method is designed to be applied anywhere in the United States, because the basic input data are always available.
Empirical Studies of Transferability of Helsinki Metropolitan Area Travel Forecasting Models
Authors: Karasmaa Nina , Pursula Matti
Published: April 2007

The temporal transferability of mode choice and trip distribution models was studied by using the data based on traffic surveys in the Helsinki, Finland, metropolitan area in 1981 and 1988. The updating procedures examined were the Bayesian updating, combined transfer estimation, transfer scaling, and joint context estimation procedures. The results of model updating indicated that finding the correct method and sample size for each case is not an unambiguous task. The best method depends on the difference in model coefficients between the initial and the final stages as well as the quality of the data. According to the statistical tests, no differences could be discerned between the models at all. However, the sample enumeration test proved that the models’ ability to predict changes in behavior can vary greatly according to the method used. On the basis of this research the transfer scaling seems to be the method best suited for simple models. In particular, the method is quite useful if the transfer bias is large. The combined transfer estimation procedure performs best when there is a great number of observations and the transfer bias is small. With small sample sizes the Bayesian approach and the joint context estimation give the best results.
Mathematical Programming Formulation of Combined Transportation and Land Use Model
Authors: Shen Pingning
Published: April 2007

A mathematical programming model of combined trip distribution, equilibrium network assignment, and residential location choice is presented. The model is developed on the basis of Wardrop’s user equilibrium principle and the random utility theory. A traveler’s route choice behavior is assumed to follow the user-optimized principle, whereas the residential location choice behavior is captured by the random utility theory. The simultaneous choice of travel routes and residential location is based on the assumption that each individual tries to minimize his or her travel cost and maximize his or her living utility. On the basis of this assumption the choice of travel routes is determined by using a user equilibrium assignment model and the choice of residential location is quantified by using a multinomial logit model. After defining the system equations of the combined model, the model is reformulated as a mathematical programming problem so that the characteristics of the combined model can be explored clearly and the model can be solved efficiently. After the properties of the model are analyzed the process of using the gradient search technique with a maximum-likelihood criterion to calibrate the model and by using the Evans algorithm to solve the optimization problem is presented. Furthermore, the model application procedure is also clearly defined.
Analysis of Discrete Choice Data with Repeated Observations: Comparison of Three Techniques in Intercity Travel Case
Authors: Raj Mehndiratta Shomik , Hansen Mark
Published: April 2007

With the acceptance and widespread application of stated preference methods in transportation analysis, there has been a need for the analysis of choice data with repeated observations. Analysis of repeated choice data is complicated by correlation of responses across the choices made by a single individual. In the probit framework, repeated choice can easily be accommodated by way of correlation in the utilities associated with the errors. However, the probit framework has computational limitations; subsequently, researchers have looked to modeling repeated choice by using extensions of the logit model. Random parameter logit models estimated by simulation methods provide a promising modeling framework. The estimation results of some stated preference intercity business travel data are compared by using three alternative estimation techniques to account for correlations across the choices made by a single individual. It is believed that two of the alternative methods, which use random-parameter logit models (developed by researchers for use in an energy application), have not been used before in the transportation context. A comparison of the three techniques provides documentation for researchers and practitioners who plan to analyze such data.
Travel Behavior as Function of Accessibility, Land Use Mixing, and Land Use Balance: Evidence from San Francisco Bay Area
Authors: Maria Kockelman Kara
Published: April 2007

The relative significance and influence of a variety of measures of urban form on household vehicle kilometers traveled, automobile ownership, and mode choice were investigated. The travel data came from the 1990 San Francisco Bay Area travel surveys, and the land use data were largely constructed from hectare-level descriptions provided by the Association of Bay Area Governments. After demographic characteristics were controlled for, the measures of accessibility, land use mixing, and land use balance—computed for trip-makers’ home neighborhoods and at trip ends—proved to be highly statistically significant and influential in their impact on all measures of travel behavior. In many cases, balance, mix, and accessibility were found to be more relevant (as measured by elasticities) than several household and traveler characteristics that often form a basis for travel behavior prediction. In contrast, under all but the vehicle ownership models, the impact of density was negligible after accessibility was controlled.
Empirical Results from Taiwan and Their Implications for Advanced Traveler Pretrip Information Systems
Authors: Jou Rong-Chang , Hu Ta-Yin , Lin Chien-Wen
Published: April 2007

A statistical analysis of travelers’ behavior is presented, and a study into the effects of pretrip information on travelers’ choice behavior is addressed. The study is based on an extensive home interview survey conducted in the Taichung metropolitan area of Taiwan. The main objectives were (a) to determine which types of information are more important to travelers; (b) to examine whether the provision of information alters the travelers’ choice behavior; (c) to relate travelers’ choice behavior, including departure time, route, and mode, to personal and travel behavior characteristics; and (d) to provide a basis for the subsequent development of a pretrip information system architecture. A binary logit model of whether a traveler switches departure time, route, mode, or any combinations of the three or does not switch after receiving traffic information is estimated. The results underscore the important relationship between the different characteristics and the propensity of travelers to change behavior. Separate binary models are developed for each of the individual trip purposes. The focus is on the urban (intraregional) trips.
Gender, Race, and Travel Behavior: Analysis of Household-Serving Travel and Commuting in San Francisco Bay Area
Authors: Mauch Michael , Taylor Brian D.
Published: April 2007

Detailed trip diary data from a 1990 survey of San Francisco Bay Area residents were used to examine the effects of race/ethnicity on the differences in commuting and household-serving travel among men and women. With respect to travel behavioral differences between men and women, the findings suggest that women do more child chauffeuring and make more household-serving trips than men. This analysis further reveals that these gender differences in commuting behavior extend to household-serving travel and can vary significantly by race/ethnicity in addition to income and household structure. It was found, for example, that commute time differences are highest among whites (4.5 min) and lowest among Hispanics (1.8 min), whereas observed gender differences in average travel time for all trips do not vary much by race or ethnicity. Furthermore, the gender variation in child-serving trips was lowest among Asians and Pacific Islanders (women are 60 percent more likely to make such trips) and highest among whites (women are 223 percent more likely to make such trips). Finally, and in contrast to child-serving travel, women make about 75 percent more grocery trips than men, regardless of race/ethnicity. The analysis suggests, however, that much, although not all, of the racial/ethnic variation in the travel behavior of men and women is probably explained by factors—such as income, employment status, metropolitan location, and automobile availability—that tend to vary systematically by race ethnicity. In general, it was found that gender is a far more robust predictor of child-serving and grocery shopping trips than either race or ethnicity.
METROPOLIS: Modular System for Dynamic Traffic Simulation
Authors: De Palma André , Marchal Fabrice , Nesterov Yurii
Published: April 2007

METROPOLIS proposes an interactive environment that simulates automobile traffic in large urban areas. The core of the system is a dynamic simulator that integrates commuters’ departure time and route choice behaviors over large networks: Drivers are assumed to minimize a generalized travel cost function that depends on travel time and schedule delay. This simulator is based on a behavioral driver information process. It allows real-time and off-line simulations. The system also includes a scenario builder and a graphical results viewer. The main ideas underlying METROPOLIS are presented, and preliminary computer simulation experiments are discussed for Geneva, Switzerland.
Why Aren’t More People Telecommuting?: Explanations from Four Studies
Authors: Pratt Joanne H.
Published: April 2007

Despite the proven “bottom-line” benefits of telework, companies are still reluctant to implement new ways of organizing their workforces. That is particularly true of the practice of allowing employees to work from home offices. The findings of four studies that identify factors that must be considered in overcoming the barriers to telework are presented: (a) a report of the Telecommute America! public-private effort to promote awareness and understanding of telecommuting and telework; (b) a survey of Houston, Texas, employers required to submit trip reduction plans under the Clean Air Acts; (c) an evaluation of the city and county of Denver, Colorado, TRP 2000 training program, and (d) the Dallas-Fort Worth, Texas, telecommuting assistance initiative of the North Texas Clean Air Coalition.
Contribution of Fine Aggregate Angularity and Particle Shape to Superpave Mixture Performance
Authors: Huber Gerald A. , Chris Jones J. , Messersmith Paul E. , Mike Jackson N.
Published: April 2007

The Superpave system is being implemented by state highway agencies. Many states implemented the asphalt binder specification during 1997. The volumetric mix design system, however, is being actively implemented. By the end of 1997, more than 200 Superpave projects had been built in the United States. As states consider specification changes necessitated by Superpave implementation, some questions are being raised. Fine aggregate angularity (FAA) requirements, one of the aggregate consensus properties, has generated considerable debate in some areas of the country. Adopting an FAA requirement of 45 percent for high traffic pavements has changed the number of sources available for asphalt mixtures. Superpave also provides a limit on flat and elongated particles. The aggregate properties requirements have increased interest regarding the basis of the specification and the values specified. The results of a limited cooperative study by industry and agencies to evaluate the role of FAA and particle shape on asphalt mixture properties are presented. A Superpave mixture design for high equivalent single-axle loads was evaluated. The fine aggregate used in the mixture design, with an FAA of 48, was replaced by other fine aggregates with lower FAA values. Properties of the mixtures containing the different fine aggregates were evaluated by using the asphalt pavement analyzer, the couch wheel tracker (a variation of the Hamburg rut tester), and the Superpave simple shear tester. A study to evaluate the sensitivity of the Superpave gyratory compactor and the Superpave mixture design system to differences in particle shape also is presented.
Superpave Field Implementation: Florida’s Early Experience
Authors: Musselman James A. , Choubane Bouzid , Page Gale C. , Upshaw Patrick B.
Published: April 2007

Over the past 10 to 15 years, Interstate pavements in northern Florida have experienced a significant number of failures, primarily due to rutting. It was believed that the present fine-graded, 50-blow Marshall-designed mixes were inadequate to withstand current loading conditions. The newly developed Superpave system represented an opportunity to address several of Florida’s asphalt pavement problems. Thus, the Florida Department of Transportation made a concerted effort to implement Superpave technology in 1996. During this period, eight projects were changed from the traditional Marshall mix designs to Superpave. Although the new procedure offers potential for improved pavement performance, there has been very little experience nationally with its field application. Florida’s early experiences with the field implementation of Superpave are documented.
Permeability Specifications for High-Performance Concrete Decks
Authors: Ozyildirim Celik
Published: April 2007

Durable concrete exposed to the environment requires a proper air-void system for protection against cycles of freezing and thawing. Durable concretes also must have low permeability to resist the infiltration of harmful solutions into concrete. Work was conducted by the Virginia Department of Transportation (VDOT) on the permeability of concretes. Information is provided on permeability, recent VDOT efforts with a low-permeability specification, and the field application of the low-permeability specification.
Shrinkage of High-Performance Concrete Overlays on Route 60 in Virginia
Authors: Sprinkel Michael M. , Ozyildirim Celik
Published: April 2007

Thin concrete overlays are widely used to protect decks against corrosion caused by the infiltration of chloride ions. These overlays are designed to have low permeability and to be free of cracks that may adversely affect the performance of the deck by facilitating the penetration of chloride ions. Sixteen high-performance concrete overlays with 13 concrete mixtures placed on two bridges were evaluated, with an emphasis on shrinkage characteristics. One overlay was constructed with concrete containing a new shrinkage-reducing admixture. Specimens prepared with this admixture had the lowest shrinkage. Based on a visual survey, all overlays were performing satisfactorily at 1 year after placement.
Influence of Early Age Volume Changes on Long-Term Concrete Shrinkage
Authors: Holt Erika E. , Janssen Donald J.
Published: April 2007

Volume changes can occur in concrete during the first 24 hr and are generally missed in laboratory shrinkage evaluations. Unfortunately these early age volume changes are present in real pavements and structures and can contribute to the cracking behavior of the concrete at later ages. Early age volume changes can occur in two forms: drying shrinkage before the start of curing and autogenous volume changes. Although these early age volume changes are often dismissed as being insignificant, recent work in Europe has identified magnitudes for early age volume changes of some concretes that are equal to or greater than 28-day drying shrinkage measurements. Expansions have also been identified in some cases. The results of some investigations of volume changes in concrete during the first 24 hr under both drying and nondrying conditions are presented. An example of potential long-term cracking under partially restrained conditions (concrete slab-on-grade modeled by a concrete ring cast around a hollow steel ring) is used to illustrate the magnitude of influence of early age volume changes on concrete cracking. Both test procedures employ nonstandard methods to quantify the cracking potential of concrete.