bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Geographic Information Systems to Inform Bus Maintenance Base Location Decisions: Sketch-Level Methodology for Estimating Bus Deadhead Costs
Authors: Shelton David , Haufschild Daniel , Pedley Justin , Spillar Robert
Published: April 2007

In making a decision to redesign a cramped or inefficient maintenance facility within a built urban environment, the cost of relocation must consider the change in operating costs due to rerouting transit routes and potentially changed deadhead costs (i.e., those costs associated with the trip a bus vehicle takes between the maintenance base and the start or end of a route). A sketch-level method for estimating bus deadhead costs that can serve as an input to high-level decision-making processes is described. In a recent analysis for TransLink in Vancouver, British Columbia, Canada, this methodology helped to quantify the total net change in deadhead costs associated with various location options. A geographic information systems (GIS) tool was used to calculate the shortest path among alternative maintenance base locations and start and end points of bus routes. Shortest-path calculations were based on estimated travel speeds, congestion, and known geographic constraints provided by the operator. Total deadhead-related costs were then estimated for each of the three maintenance base location options under consideration. The difference between these costs served as one component in the decision-making process, along with other factors such as property acquisition and construction cost. This analysis serves as an example of how GIS use can provide a low-cost sketch-planning tool to inform investment decisions.
Safety of Efficiency: Link Between Operational Performance and Operational Errors in the National Airspace System
Authors: Hansen Mark , Zhang Yu
Published: April 2007

Safety and efficiency are two of the most important goals of the national airspace system (NAS). However, these goals are typically viewed as competing or independent, rather than complementary. The complementary aspect of safety and efficiency is illustrated from the point of view of human factors and ergonomics. Statistical methods were used to analyze safety and efficiency performance measurements, operational errors, and daily flight time index (DFTI). Factors related to weather and complexity were found to be more likely on days with poor operational performance as measured by DFTI. The results indicate a positive relationship between NAS safety and efficiency and imply that NAS safety performance may be improved by increasing efficiency, and vice versa.
Economic Benefits of Increased En Route Sector Capacity from Controller-Pilot Data Link Communications
Authors: Bennett Michael J. , Knorr Dave , Rakas Jasenka
Published: April 2007

The En Route Controller-Pilot Data Link Communications (CPDLC) program is designed to enable digital data communications between controllers and pilots. CPDLC Build 1A has been proposed as the first step in the nationwide rollout of this program to en route airspace by implementation in eight air route traffic control centers. Because CPDLC will automate several routine air-ground communications tasks, one potential benefit is reduced controller workload, which could lead to increased sector capacity and thus reduced flight times for flights traversing busy sectors. To quantify the workload reduction, a comparison has been made of the time currently required to perform communications tasks, as determined from recordings of actual air-ground communications, and the time required to perform the same tasks with CPDLC, as determined by a controller-in-the-loop simulation. This comparison indicated the potential for a significant reduction in the time spent on controller-pilot communications. A model was constructed to relate the reduced controller communications workload to increased sector capacity. The National Airspace System Performance Analysis Capability (NASPAC) model was used to estimate the reduction in flight times associated with the modeled sector capacity increase. NASPAC was run for both an idealized good weather day and a sample actual bad weather day. By 2017, the last year of the projected economic lifetime of CPDLC, average flight time savings from CPDLC-related capacity increases were estimated to exceed 9, 400 min/day.
Washington State's Web-Enabled Pavement-Management System
Authors: Muench Stephen T. , White George C. , Mahoney Joe P. , Turkiyyah George M. , Sivaneswaran Nadarajah , Pierce Linda M. , Li Jianhua
Published: April 2007

WebWSPMS is an Internet application that allows Washington State Pavement Management System (WSPMS) data to be accessed and analyzed via the World Wide Web. With WebWSPMS, data can be searched, browsed, and accessed either textually or spatially and displayed in a web format. Data available to users include, but are not limited to, roadway geometric data, pavement surveys, performance projections, historical project data, traffic data, and a complete set of digital images for the entire Washington State Department of Transportation (WSDOT) road network. Access is readily available to all authorized users and requires only a computer, a web browser, and an Internet or intranet (for WSDOT personnel) connection. The increased access and analysis capabilities offered by WebWSPMS allow much greater and easier use of the system by both experts and novices alike, which has the potential to increase efficiency and produce more varied and novel approaches to data analysis. Overall, this effort improves WSDOT's ability to develop knowledge, relationships, and models to facilitate improved pavement planning, design, construction, rehabilitation, and performance predictions for Washington State pavements. The envisioned complete WebWSPMS product is described, with examples provided from the current development effort, which is available online at http://hotmix.ce.washington.edu/wspms.
Collecting and Interpreting Long-Term Pavement Performance Photographic Distress Data: Quality Control-Quality Assurance Processes
Authors: Rada Gonzalo R. , Simpson Amy L. , Hunt John E.
Published: April 2007

The Long-Term Pavement Performance (LTPP) program is making use of photographic technology to provide, first, detailed, distress-specific condition data for use in the development and validation of pavement performance models and, second, a permanent, objective, high-resolution record of pavement condition over the full length and width of the sections in the program. Because high-quality distress data are critical to the success of the LTPP program, numerous quality control-quality assurance (QC-QA) processes have been implemented over the life of the program. Those processes address data quality before the start of data collection, during data collection, during data interpretation, after data interpretation, and after the uploading of data to the LTPP database. Some of the processes are a direct result of advance planning, based on past experience, while others are the result of lessons learned in the course of the program. Some were implemented early in the program, while others were introduced well into the program. The Distress Identification Manual, distress rater accreditation workshops, time series review, database checks, data studies and analyses, and feedback reports are just a few of the elements that make up the full suite of QC-QA processes. A detailed summary of the QC-QA processes associated with the LTPP photographic distress data is presented.
Methodology to Evaluate the Flail Space Model by Using Event Data Recorder Technology
Authors: Gabauer Douglas , Gabler Hampton C.
Published: April 2007

The flail space model, which was developed in the 1980s, has become the standard method for estimating occupant risk in full-scale crash tests involving roadside safety features. The widespread availability of air bags and increased seat belt usage rates in today's vehicle fleet, however, raise serious questions concerning the validity of the model. Recent installation of event data recorders (EDRs) in a number of late-model vehicles presents a different perspective on the assessment of the validity of occupant risk based on the flail space model. EDRs are capable of electronically recording data such as vehicle speed, brake status, and throttle position just before and during an accident. Of particular interest is the EDR's ability to document the deceleration of a vehicle during a collision event. A methodology using EDR data to investigate the capability of the flail space model to predict injury to air bag-restrained occupants and results of a preliminary analysis based on implementation of the developed methodology on a limited data set are presented. Most of the analysis is limited to the occupant impact velocity because of insufficient data for evaluation of the occupant ridedown acceleration. The longitudinal occupant impact velocity was found to be a good predictor of overall injury, chest injury, and, to a lesser extent, lower extremity injury. For the head and upper extremity body region, the longitudinal occupant impact velocity is a weak predictor of injury.
Compatibility of Vehicles with Safety Barriers: Head Ejection Through Side Windows
Authors: Giavotto Vittorio
Published: April 2007

The safety performance of roadside features may depend not only on barrier but also on vehicle behavior. Best results require efficient synergy of barrier and vehicle, or compatibility. Examples of problems where such compatibility may be needed are discussed. One of these problems—head ejection in collisions with high-containment barriers—was investigated with an accident survey, full-scale tests, and laboratory sled tests. One of the conclusions is that, with high-containment barriers suitable for narrow medians, partial head ejection occurs systematically and may represent a high risk. Head containment in such collisions should be mandatory for crashworthy vehicles. This can be easily obtained with laminated glass, without window frame reinforcement. The conclusion is that vehicle and barrier crashworthiness standards should be linked. Collisions with safety barriers are statistically significant events and should be considered among vehicle passive safety items.
Multidimensional Framework for Context-Based Design of Major Urban Thoroughfares
Authors: Dock Frederick C. , Bochner Brian S. , Greenberg Ellen
Published: April 2007

During the post-World War II period, conventional roadway design has been based on a functional classification system that addresses levels of vehicle movement and access to abutting properties. Traffic-carrying capacity has been the dominant consideration. In recent years, more attention has been given to other characteristics of local streets and a small number of major streets. New design standards have been developed for local (neighborhood) streets by some organizations and local agencies. At the same time, the National Environmental Policy Act has increased the importance of environmental considerations in the design of major streets and roads and highlighted the importance of minimizing impacts of roadway projects on natural resources, particularly in rural environments. However, no widely accepted design guidelines have yet been developed for urban major streets. Street design and urban design professionals share a need for a two-dimensional framework that ties together ( a) roadway design criteria for an expanded palette of street types (number of lanes; target speed; pedestrian, transit, bicycle, and motor vehicle functions; other functional criteria) and ( b) a set of place types that reference features of both the public right-of-way and private development fronting on the roadway and in the broader area. The conventional functional class-based design criteria do not satisfy this need. The basic structure of such a framework is discussed.
Field and Laboratory Investigation of Permeable Asphalt Mixes on Georgia Highways
Authors: Brandon James M. , Jared David M. , Wu Peter Y. , Geary Georgene M.
Published: April 2007

The Georgia Department of Transportation (GDOT) investigated possible high permeability in asphalt mixes statewide in response to reports of prolonged wetness on pavements around the state after rainfall. In these locations, high permeability manifested itself as wet areas on pavement surfaces where wetness remained after natural conditions should have removed all moisture from the surfaces. Sixteen project sites were inspected for problem areas statewide, and core specimens were taken from six of the sites. Specimens were taken from areas considered representative of the problem areas in each project. The specimens were tested to determine the permeability, bulk specific gravity, maximum theoretical specific gravity, percentage of air voids, percentage of asphalt cement, and gradation of the mix. According to the findings of this investigation, some Superpaver; mixes that were designed in accordance with GDOT specifications exhibited undesirable permeability. The investigation determined that both mix design and construction contribute to permeable mixes; hence, permeability problems are to be corrected by a balanced adjustment to these processes, according to the following recommendations: ( a) for each Superpave mix type used in Georgia, develop mix-specific acceptance criteria for maximum in-place air voids; ( b) include evaluation of mix permeability in mix design; and ( c) provide continued quality control during construction operations to ensure the success of the mix-specific acceptance criteria.
Evaluation of Moisture Sensitivity of Bituminous Mixtures by a Complex Modulus Approach
Authors: Pinzón Eduardo Castañeda , Such Christian
Published: April 2007

Various laboratory tests are used to evaluate the moisture sensitivity of bituminous mixtures. However, most of them are destructive and require a large number of specimens. Consequently, they do not permit continuous monitoring of the deterioration in mechanical performance, much less measurement of the recovery of this performance, as water evaporates during the drying process. Monitoring of the stiffness modulus could provide a clearer picture of the process of deterioration and recovery that occurs during an immersion-drying cycle. However, during the specimen immersion phases, bitumen ages and hardens, and its stiffness modulus increases. Thus, the action of water simultaneously produces deterioration in the bitumen-aggregate bond and hardening of the binder; these two processes lead to opposing responses and prevent making a clear appraisal of the bituminous mixture's ability to withstand the action of water. Evaluating the mechanical characteristics of bituminous mixtures with a Cole—Cole plot or in black space provides new possibilities for isolating the effect of water at the bitumen-aggregate interface from the effect of the binder.
Results of Integrating Simple Performance Tests and Environmental Conditioning System
Authors: Tandon Vivek , Kambham Babu S. , Bonaquist Ramon , Solaimanian Mansour
Published: April 2007

Under the guidance of the Strategic Highway Research Program, an environmental conditioning system (ECS) was developed to simulate field conditions to identify the moisture sensitivity of asphalt concrete mixes. However, the system was not included in Superpaver because of poor repeatability. Studies conducted at the University of Texas at El Paso improved the prediction capabilities of the conditioning system. The modified system uses resilient modulus as a moisture sensitivity indicator. Resilient modulus has been commonly used by highway practitioners as an indicator of hot-mix asphalt concrete performance. However, as an extension to the Superpave system, under NCHRP Project 9-19, researchers have proposed simple tests to evaluate the performance of asphalt concrete. These tests are referred to as dynamic modulus, flow number, and flow time. The objective of this study was to evaluate the potential of these tests, when integrated with an ECS, to predict moisture damage in lieu of the resilient modulus. Three mixes of known performance were selected and conditioned by using a conditioning procedure of the modified system. The simple performance tests were done on unconditioned as well as ECS-conditioned specimens. The integration results indicate that the flow number and flow time tests, as conducted during this study, do not have the potential to replace resilient modulus in ECS for identification of moisture-susceptible asphalt concrete in the present form. However, the dynamic modulus test demonstrated their potential as a performance indicator replacing the resilient modulus test. The results of the integration efforts are presented here.
Implications of Experimental Measurements and Analyses of the Internal Structure of Hot-Mix Asphalt
Authors: Masad Eyad , Button Joe
Published: April 2007

This study summarizes the experimental and analysis methods used in characterizing and quantifying the internal structure of hot-mix asphalt (HMA) paving mixtures. The implications of the internal structure analysis for the design, compaction, and performance of HMA are also discussed. The methods can be divided into two categories: volumetric analysis methods and imaging methods. The volumetric analysis methods rely on bulk measurements of the percentage of air voids in certain aggregate sizes or in the whole mix as indicators of packing. These concepts are currently used in the Superpaver design system for densegraded HMA, stone matrix asphalt design, and the Bailey method for selection of aggregate gradations in HMA. The imaging methods quantify the distribution of the aggregate skeleton, voids in the mineral aggregate, and air voids by analyzing images of the internal structure. These images can be captured two-dimensionally with a simple setup of a microscope connected to a camera or three-dimensionally with an X-ray computed tomography system.
Performance of Schuyler Heim Composite Bridge Deck Replacement: Port of Los Angeles, California
Authors: Lewis Andrew E. , Dumlao Chris , Lee Michael J. , Weinmann Thomas L.
Published: April 2007

Details are given of the California Department of Transportation's first installation of fiber-reinforced polymer panels that are instrumented during the fabrication process for the replacement of existing fatigued open-grated steel deck panels. Open-grated steel decks have historically been used on movable bridges because they are lightweight. Unfortunately, more effort is required to maintain an acceptable skid resistance, and their ride quality is less than that of a solid deck. Once the deck begins to fail, it is not easily rehabilitated and usually must be replaced at significant cost. Schuyler Heim Bridge, Br. No. 53-2618, is one of those structures; it has an open-grated steel deck in its lift span that is rapidly failing, well before its expected service life. The deck requires replacement. The structure, which is located in District 7 on Route 47, post mile 4.0, crosses the Cerritos Channel of the Los Angeles Harbor. The development of lightweight composite materials presents a unique opportunity; these materials can provide the benefit of a deck with a solid roadway surface for bridge structures that need lightweight decks. This deck is to be used as an example in the development of specifications for the design of future deck-replacement projects. Therefore, the focus of the design should be to produce an economical deck using materials that are nonproprietary and readily available with component shapes that can be produced without exorbitant tooling costs. Instrumentation installed on the deck panels monitor for longer-term behavior. Load tests are conducted monthly to determine panel performance.
Strength of Spandrel Walls in Masonry Arch Bridges
Authors: Erdogmus Ece , Boothby Thomas E.
Published: April 2007

Previous research on the strength of masonry arch bridges has focused on the carrying capacity of the arch barrel in the span direction. Although the results of a spandrel wall collapse may be very serious, the transverse strength of masonry arch bridges has not been widely addressed. Recent experience, however, has shown that the transverse behavior and the strength of the spandrel walls are at least as important as the behavior in the span direction. Although complex computer analysis methods have been proposed for examining the masonry arch bridge as a three-dimensional structure, these methods are not suitable for everyday practical application. An approximate analytical method for the prediction of the strength of masonry spandrel walls is developed based on the conventional analysis of fills supported by retaining walls. The method is based on the determination of loads by Coulomb-Rankine analysis and the determination of resistance by the fracture line method, similar to the yield line method for reinforced concrete slabs. A table that further increases the simplicity and speed of the method is also provided. The proposed method allows the practicing engineer to calculate a factor of safety for the transverse strength of a spandrel wall for different situations, such as moist soil, cracked wall, effect of live load for shallow fill bridges, or existence of parapet walls. Results of these conventional, simplified analyses compare favorably with observed bridge distress and results of a previously validated finite element analysis method.
Influence of Wearing Surfacing on Performance of Orthotropic Steel Plate Decks
Authors: Seim Charles , Ingham Tim
Published: April 2007

The AASHTO Bridge Design Specifications first incorporated provisions for the design of orthotropic steel plate deck bridges in 1973. This and subsequent editions as well as the technical literature provided few requirements or guidelines for the design of the wearing surface. Little information is available in the United States today to help bridge designers find suitable materials and design methods for orthotropic deck wearing surfacings. An orthotropic steel deck plate requires a wearing surfacing for skid resistance, for smooth riding, and for corrosion protection. The wearing surfacing is subjected to the heavy impact of loaded truck wheels imposed by the passage of millions of trucks during the several decades of its service life. The performance of the wearing surfacings on orthotropic decks in the United States varies from excellent to poor, depending largely on deck plate flexibility, volume of heavy-truck traffic using the bridge, and, in particular, the type and thickness of the surfacing. Influences of the thickness and modulus of wearing surfacings on the performance of orthotropic steel plate decks are presented. Graphs using AASHTO truck wheel loading are presented; they show the wheel loading demand on the wearing surfacing as a function of thickness and the n value, which is the ratio of the wearing surface modulus to the steel modulus. A successful surfacing material must have properties that meet these demands initially, as well as many millions of wheel load applications during many years of service. Laboratory testing may be required to determine the durability properties of the surfacing.
Field Monitoring of Integral Abutment Bridge in Massachusetts
Authors: Civjan Scott A. , Breña Sergio F. , Butler David A. , Crovo Daniel S.
Published: April 2007

Integral abutment bridges are increasingly being used to eliminate undesirable bridge joint effects on the long-term performance of bridges. Although many states use this type of construction, common design guidelines are lacking, and nonuniform limitations on integral abutment design are imposed by different agencies. Data from the field monitoring of an existing three-span integral abutment bridge in central Massachusetts are presented. Resulting data are valuable in evaluating existing design provisions and understanding structural behavior. The results presented for a 16-month period of monitoring include recorded ambient temperature from -4°F to 99°F (-20°C to 37°C). Longitudinal movements induced by thermal expansion and contraction of the bridge are consistent with temperature changes. However, earth pressure cell data indicate that the maximum pressures generated behind the abutment walls occur in early spring. Lower pressures measured in the summer indicate some dissipation of soil pressures with time. Longitudinal displacement measurements taken during 2-week periods included variations that approached the magnitude of seasonal changes. Although fairly significant abutment movement has been recorded to date, there is no clear indication that the abutment piles have yielded. Field monitoring will continue, and the results from this study will be used to calibrate a detailed finite element model of the bridge to validate current integral abutment bridge design practices.
Field Test and Rating of Arlington Curved-Steel Box-Girder Bridge: Jacksonville, Florida
Authors: Huang Dongzhou
Published: April 2007

A load capacity rating procedure and the results of field tests conducted on the Arlington curved-steel box-girder bridge are presented. Two Florida Department of Transportation (FDOT) test trucks with a total weight of up to 117 tons provided the static loading. One FDOT test truck with a total weight of 52.7 tons applied the dynamic loading. The actual behavior of the bridge was ascertained by comparing the field test results with those obtained from three different theoretical mechanical models. Analysis demonstrates how the actual mechanical behavior and load capacity of a curved-steel box-girder bridge can be well predicted by a proper finite element method based on as-built bridge plans. Some important parameters, such as impact factors, the effective width of the concrete slab, and the structural effect of barriers, are discussed. Finally, the load rating factors for a variety of Florida's rating vehicles were determined on the basis of a finite element model generated from field test results and analytical modeling of the bridge. The current capacity ratings are approximately 17% to 27% higher than those determined in 1988 using a conventional analytical method. The capacity increase is due mostly to the conservativeness of traditional methods and codes. The research results are instructive and applicable to bridge design and bridge load rating.
Durability of Very-Early-Strength Latex-Modified Concrete Against Freeze-Thaw and Chemicals
Authors: Yun Kyong-Ku , Kim Dong-Ho , Choi Sung-Yong
Published: April 2007

This study focused on the durability of very-early-strength latex-modified concrete against freeze-thaw and chemical exposure by using water absorption, freeze-thaw resistance, deicer salt scaling, and chemical resistance tests. The experimental variables were latex content (latex solids and cement as percentages) and water-cement ratio (w/c). This study examined five levels of latex content (0%, 5%, 10%, 15%, and 20%) at a constant slump and three w/c's (0.36, 0.38, and 0.40) at a constant latex content of 15%. The results were as follows: the water absorption at 15% latex content was less than 50% at 0% latex content and supported the theory of a continuous polymer film that hinders the penetration of water. Within the range of this study, both the latex-modified and nonmodified concrete exhibited good freeze-thaw performance, although the latex-modified exhibited superior properties. In both the weight loss and visual evaluations, the deicer salt scaling test indicated improved performance as the latex content increased. In the chemical resistance tests, the weight loss of latex-modified concrete decreased as the latex content increased for both sulfuric and hydrogen chloride acid exposures. However, in the calcium chloride solution test, the weight change varied from a slight gain with no latex to a slight loss at 20%.
In Situ Criteria of Pull-Off Test for Measuring Bond Strength of Latex-Modified Concrete Overlay
Authors: Yun Kyong-Ku , Kim Sung-Hwan , Jeong Won-Kyong , Kim Kwang W.
Published: April 2007

This study evaluated the factors influencing a pull-off test on latex-modified concrete (LMC) overlay by finite element analysis (FEA) and experimental verification and provided field engineers and project managers a guideline for measuring the bond strength in the field. The purpose of FEA was to predict stresses at the interface between the substrate and the overlay and between the disk and the overlay. Good agreement has been obtained between the theoretical and experimental results to confirm the following: the steel disc thickness did not affect the stress concentration factor (SCF) at the concrete interface but significantly influenced that of the steel disc. To prevent failure at the steel disc interface, the normalized steel disc thickness (T/D) should be at least 0.3. The effect of overlay thickness was significant to the stress distribution at the concrete interface. The normalized overlay thickness should be larger than 0.4. SCFs at all diameters decreased rapidly as the substrate coring depth increased from 0.05 to 0.2 of normalized cutting depth relative to core diameter. Those with a 75-mm diameter (D75) and a 100-mm diameter (D100) became stabilized immediately after reaching 0.2 of normalized cutting depth relative to core diameter. Stress distributions at concrete interfaces were not affected by the distance of the core from the edge of the slab (le), the distance between cores (lc), and the typical elastic modulus ratio of LMC to conventional concrete. The experimental results with the major influencing factors (steel disc thickness, core diameter, and partial cutting depth) showed good agreement with FEA results. For theoretical as well as for practical purposes, 100-mm (4-in.) core diameter is optimum; cutting depth should be between 25 mm (1 in.) and 40 mm (1.7 in.).
Relationship Between Elastic Modulus and Permeability of Damaged Concrete
Authors: Dilek Ufuk , Leming Michael L. , Guth Dena
Published: April 2007

The study examined the effects of selected damage mechanisms on the dynamic elastic (Young's) modulus (Ed) and air permeability index (API) of concrete. The relationship between Ed and API in damaged concrete and the use of Ed and API to determine both the extent of damage due to various exposures and the presence and extent of damage gradients are reviewed. The Ed and API were determined by using 25-mm-thick disks sawed from high-strength and conventional- strength concrete cylinders, before and after static fatigue damage; from cores removed from a lightweight, precast, prestressed concrete beam after exposure to intense fire; and from cores removed from an elevated concrete slab after exposure to thermal shock and subsequent cryogenic temperatures. The findings of the study suggested that Ed and API were linearly related for a given set of raw materials until damage was significant, that analyzing concrete disks at 25-mm (1-in.) depths provided insight into damage gradients, and that the durability of high-strength concrete in service may have been better than conventional-strength concrete under similar stress conditions. Ed and API were found to be effective tools in the assessment of damaged concrete and gradients of damage. API was found to be particularly sensitive to fire damage and associated severe drying.
Modeling Impact of Emerging Uncertain Time-Dependent Aggregate Activity-Travel Patterns on Individual Activity Participation and Timing Decisions
Authors: Han Qi , Dellaert Benedict , van Raaij Fred , Timmermans Harry
Published: April 2007

Existing activity-based models are typically concerned with predicting observed aggregate activity-travel patterns. The interaction and dependencies between individuals have received less attention. Considered here is how one specific schedule choice, namely, the start time of an activity chosen by an agent, aggregates to form an equilibrium distribution, which in turn influences individual decision making. These choices are formalized as the outcomes of a game of incomplete information in which agents have to conjecture the behavior of other agents. The properties of the model are examined by using numerical computer simulations. The results of the simulations support the face validity of the formulated model.
Are Attitudes Important in Travel Choice?
Authors: Parkany Emily , Gallagher Ryan , Viveiros Phillip
Published: April 2007

A huge body of literature in social psychology describes 70 years of theory and experimentation relating attitudes to behavior. Much of it suggests a stronger causal link between choices and attitudes than that between attitudes and choices—attitude models conditioned on revealed choice explain more than knowledge of peoples' attitudes and determination of what choice they will make. Alternative analyses suggest that attitudinal and other data should be used to determine respondents' intentions rather than their desires to better predict behavior. Attitude studies are becoming more prevalent in the study of transportation behavior, but researchers vary in what kinds of attitudes are considered and how attitudes influence the transportation decision process. The social psychology literature is briefly highlighted, transportation applications are reviewed, and a case study is presented. Cognitive, affective, and behavioral attitudes help explain the intentions of those surveyed for the case study. These results and the literature suggest that attitudes are very important, but caution is recommended regarding survey wording and capturing behavior intentions. In addition, the results suggest that to explain behavior, a circular behavior process including attitudes is better at explaining choices compared with the use of only cognitive and affective attitudes.
Computerized Household Activity-Scheduling Survey for Toronto, Canada, Area: Design and Assessment
Authors: Doherty Sean T. , Nemeth Erika , Roorda Matthew , Miller Eric J.
Published: April 2007

Traditional activity-travel diary surveys have for some time served as the primary source of data for understanding and modeling travel behavior. Recent changes in policy and forecasting needs have led to the development of an emerging class of activity-scheduling process surveys that focus on the underlying behavioral mechanisms that give rise to travel and condition future change. Many of these surveys involve the use of computers for data entry over multiday periods. These changes pose new challenges and opportunities for quality assessment. At this early stage it is more important than ever to document closely the quantity and quality of data provided by such surveys as well as the associated burden and experience of respondents. This study reviews existing quality standards and seeks to develop several new data-quality measures suitable to this emerging class of surveys. Data are used from a recent household activity-scheduling survey of 271 households in Toronto, Ontario, Canada. A detailed description of the survey instrument is provided, along with an in-depth examination of key results that shed light on data quality. Included are results from a separate survey of 31 respondents concerning their experiences and perceptions of the survey. Overall, although the survey was generally successful in tracking both observed patterns and underlying decision processes over a multiday period within a household, it did come at a price in terms of respondent burden. On the basis of these results several new data-quality guidelines are suggested that incorporate use of activity-trip rates, scheduling-step rates, planning-time horizons, and log-in durations. Further specific suggestions for reducing respondent burden are suggested.
Urban Networks with Ring Roads: Two-Level, Three-Player Game
Authors: van Zuylen Henk J. , Taale Henk
Published: April 2007

The integrated traffic control and traffic assignment problem is studied for a situation with two road authorities. Road authorities try to optimize their own objectives, and the same is done by road users. The result is a two-level, three-player multistage optimization problem with complete information. Game theory gives a suitable framework to analyze the problem and to find solutions for different situations such as no cooperation, cooperation between the two authorities, and a system optimum in which all actors cooperate to minimize the total costs for all travelers. Two approaches are used: an analytical approach and one based on a simulation and assignment framework. Both approaches are described and used to study a simple example, for which the results are given and discussed. The results show that separate or integrated anticipatory control gives better results than iterative reaction to the current situation. If one road authority takes the lead and anticipates the reactions of both the road users and the other road authority, a suboptimum is reached. The model calculations provide evidence that cooperation of road authorities improves utilization of the infrastructure and that global optimization does not necessarily result in a worse situation for one road authority.
Metropolitan Planning Organization Voting Structure and Transit Investment Bias: Preliminary Analysis with Social Equity Implications
Authors: Nelson Arthur C. , Sanchez Thomas W. , Wolf James F. , Beth Farquhar Mary
Published: April 2007

Metropolitan planning organizations (MPOs) are the conduit through which billions of federal and state transportation dollars are funneled annually for regional transportation facilities. MPO transportation investments are guided by long-term regional transportation plans that are implemented through short-term transportation improvement plans. Because transportation investments shape land use patterns, decisions by MPOs have important implications for regional land use patterns and, by implication, social equity. For their part, MPO decisions are made by a board whose composition varies widely across the nation. They are not elected to serve on the MPO, however, and MPOs are not required by federal law to have balance in voting. Therefore, the potential exists for MPO decisions to be biased and favor certain investments beneficial to particular metropolitan areas' interests at the expense of others. This study reviews MPOs generally, discusses variation in their voting structures, and reports results from a statistical analysis on the pattern of transportation investments with respect to MPO voting structure. It was found that for each suburban MPO voting member, controlling for other factors, MPO investments are shifted 1% to 9% away from transit (and other modes) to highways. Implications for land use patterns and especially social equity are described. More research should be undertaken, however, to confirm whether and the extent to which such bias exists.
Montana Secondary Program Reform and Application of Goals Achievement Methodology to Project Prioritization
Authors: Straehl Sandra S. , Schintler Laurie
Published: April 2007

A methodology for prioritizing transportation funding in diverse rural environments is described based on experiences in the state of Montana. In 1999, the state of Montana redesigned its secondary highway-funding program. The amended statute allocated federal-aid and state matching funds by formula to each of Montana's five transportation districts and terminated a county-level suballocation that had been in place for more than 30 years. Instead of creating regional planning organizations or formal decision-making bodies such as "councils of governments," the Montana counties statutorily retained direct decision-making authority to set funding priorities, but at the district level. Through a cooperative process, the state of Montana and its 56 counties developed a goals achievement methodology for project prioritization that is responsive to a broad range of transportation needs and goals across all transportation districts of the state. This methodology is applicable for roads with very diverse characteristics and for decision makers with very different goals for the transportation systems under their jurisdiction. The methodology has the advantage of supporting a regional approach to funding prioritization. In addition, it has overcome the funds management problems that had occurred in the Montana secondary program with funds suballocated into 56 individual county accounts. Benefits and problems associated with direct suballocation of transportation resources were studied and the reformed Montana program was evaluated in terms of retaining the benefits and addressing the problems.
Evaluation of Network Preloads on a Medium-Sized Urban Travel Forecast Model
Authors: Anderson Michael D. , Olander Justin P. , Gholston Sampson E.
Published: April 2007

Transportation engineers and planners attempt to understand urban travel characteristics to develop, formulate, and analyze problems and opportunities better. Transportation professionals use urban transportation models and typically implemented the four-step urban transportation planning process. This study examined a modified planning process that preassigned external trips to the transportation network before distributing and assigning internal trips. The preassignment, or preloading, of external trips helped to ensure that trips passing through the network were assigned to only the major through routes and that internal trips were modeled with the knowledge that external trips were present on the roadways before selecting destination or route. The study concluded that the preload methodology did not affect the validity of a travel model in a medium-sized urban travel forecast model and reduced assignment error on minor arterial roadways, which would not be the typical routes used by external travelers, to a level below the maximum deviation where an incorrect decision would be made regarding improvements to the roadway infrastructure.
Calibration and Validation of Quick Response Forecasting Parameters for Cities in Rural Counties of South Carolina
Authors: Sarasua Wayne , Clarke David B. , Reiff Richard , Sabb Veretta
Published: April 2007

Quick response travel forecasting techniques have been applied extensively since they became prevalent in the late 1970s. These techniques involve using transferable parameters developed from survey and other empirical data to assist transportation planners to model small urban areas with populations greater than 50,000. The usefulness of the quick response techniques and parameters that are currently in wide application are questionable for cities in rural counties because they were not originally designed for use in areas with populations of fewer than 50,000 people. The research described addresses a critical need for planning tools oriented to smaller cities. This project focused on developing transferable travel demand forecasting parameters that targeted areas of the state of South Carolina with diverse populations and per capita incomes lower than the national average. The findings of this project should allow planners throughout rural areas of South Carolina and similar states to make more reliable estimates of future traffic identified in long-range plans. The calibrated parameters also should be useful for cities in other states that have fewer than 50,000 people and that have demographic and socioeconomic characteristics similar to those of the cities that were modeled as part of this research.
Computer-Based Multimedia Pavement Training Tool for Self-Directed Learning
Authors: Muench Stephen T. , Mahoney Joe P.
Published: April 2007

Advances in technology, more retirements, and less-experienced personnel have increased demand for training within the pavement industry. Traditionally, training demand has been met by classroom short courses. Although many are excellent, these courses can take substantial time to develop and deliver, and they have trouble reaching everyone who needs or desires training. The term "self-directed learning" (SDL) refers to learning and teaching methods that rely on the direction and guidance of the learner. Examples are distance learning and learning from computers or television. When combined with short courses, SDL offers the potential to extend training outreach and improve the quality and productivity of instructor-student contact hours within short courses. The Pavement Guide was developed to investigate the feasibility and effectiveness of SDL tools for use in pavement training. Pavement Guide refers to the generic concept of a computer-based multimedia CD-ROM training tool that provides general and detailed pavement knowledge. This concept has been used to produce several customized Pavement Guide versions, the largest of which consists of 275 web pages, 2,500 images, 50 animations, 14 videos, and 11,000 hyperlinks, all of which can be delivered on one CD-ROM. On the basis of early student surveys, initial reaction to the Pavement Guide concept has been good, which indicates that development of such SDL products is a viable field into which pavement training should expand. The Washington State Department of Transportation (WSDOT) version, the Pavement Guide Interactive, is available for viewing at hotmix.ce.washington.edu/wsdot_web/WSDOT_intro.htm.
Thickness Tolerance for Portland Cement Concrete Pavements
Authors: Kim Seong-Min , McCullough B. Frank
Published: April 2007

The thickness tolerance limit currently used by the Texas Department of Transportation for portland cement concrete pavements was developed about 50 years ago, when the pavement thickness was normally less than 10 in., and no additional study on the tolerance limit has been conducted since its development. Because the current thickness tolerances are independent of the design pavement thickness, they are very tight, especially for thicker pavements. These tight tolerances give difficulties in construction and in the use of nondestructive testing (NDT) methods for slab thickness determination because errors of NDT methods depend on the thickness. In this study, the sensitivity analysis of the slab thickness has been conducted to investigate whether the current thickness tolerance can be loosened and to propose acceptable thickness tolerance limits. The concepts to find the thickness tolerance have been developed on the basis of various methods, including the AASHTO pavement life prediction equation, the mechanistic distress prediction model, and fatigue failure models. The sensitivity of slab thickness to pavement performance has been investigated with those methods. The analysis results clearly show that the thickness tolerance should be dependent on pavement thickness. On the basis of the analysis results, reasonable approaches for thickness tolerance determination have been proposed.
Early-Age Curling and Warping Behavior: Insights from a Fully Instrumented Test-Slab System
Authors: Jeong Jin-Hoon , Zollinger Dan G.
Published: April 2007

A concrete slab was constructed at Texas A&M University to study temperature, moisture, and creep effects on the curling and warping behavior of jointed concrete pavements under different curing conditions. A saw-cut joint was placed at the mid-slab location, where one half of the slab was cured with a standard curing compound and the other half was mat-cured. The half of the slab under membrane curing was subjected to a larger built-in curling and shrinkage than the half that was mat-cured. Because of differences in the amount of shrinkage and creep between the two curing methods during the hardening process, the two halves of the slab showed different early-age behaviors with respect to strain and vertical displacement. The dowels also affected the early-age behavior of the slab at the saw-cut joint. A linear relationship was found among measured vertical corner displacements, concrete strain, and calculated dowel bending moments. The equivalent temperature differences calculated by ISLAB 2000 present the effects of shrinkage and creep on the curling and warping behavior of the slab.