bluuebunny/crossref_metadata_2025 huggingface dataset:
Options Approach to Risk Analysis in Transportation Planning
Authors: Brand Daniel , Raj Mehndiratta Shomik , Parody Thomas E.
Published: April 2007

The applicability of the real-options approach to risk management to the metropolitan transportation planning process is described. The options approach to risk analysis brings to investment decisions the insight that there is an inherent value in option-creating actions (by resolving uncertainty, enabling flexibility, or uncovering new and relevant information) and a cost associated with exercising options (irreversible commitments of resources and time). The options approach moves investment decision making from simply choosing whether to build a project to a regime that considers a range of possible decisions, with the potential value of each decision measured in terms of its option-creation value and irreversible commitment cost. This approach is specifically designed to maximize the value of investments having the characteristics of transportation projects that are subject to uncertainty and risk in their outcomes. Also described is the new options approach; examples that illustrate the value of different kinds of options are given. By recognizing the value of improved information—and actions to obtain it—the options approach can give real impetus to improved planning methods. Because the analysis tools provided by the options approach make it possible to value the additional information that improved planning can provide, recommendations are provided on how—and in what parts of the metropolitan transportation planning process—the new tools of risk analysis can most appropriately be applied.
Public Involvement in Transportation Planning in the Washington, D.C., Region: Report on an Assessment
Authors: Graves Scott , Casey Sean
Published: April 2007

In the summer and autumn of 1998, the National Capital Region Transportation Planning Board (TPB) sponsored an independent study by a team led by ICF Kaiser (now ICF Consulting) to assess its public involvement program for transportation planning carried out in the Washington, D.C., region. The Washington region’s metropolitan planning organization was one of the first to commission an assessment of its public involvement efforts as required under the Intermodal Surface Transportation Efficiency Act of 1991. The purpose was to provide an overall assessment of TPB’s public involvement program and recommend options for improvement. The assessment was conducted in three phases. The first phase was to review public involvement efforts in the Washington region and, for comparative purposes, other selected metropolitan regions across the United States. The second phase was to interview knowledgeable stakeholders on public involvement in the Washington region. The final phase was to prepare a report presenting findings and recommendations to the TPB based on the efforts from the first two phases. The final report was organized under the umbrella of four overarching themes: ( a) strengthen outreach to stakeholders and the public; ( b) enhance access to information; ( c) improve the public’s understanding of TPB responsibilities; and ( d) either discontinue or enhance the citizens’ advisory committee. Although the first three themes are familiar to strengthening many public involvement programs, the fourth is somewhat new and surprising, especially given the prevalence of such bodies.
Friction Correction Equation for the Dynamic Cone Penetrometer in Subsoil Strength Testing
Authors: Livneh Moshe
Published: April 2007

Extensive experience gained with the dynamic cone penetrometer (DCP) in Israel has led to some modifications in both the testing apparatus and the testing procedure. One such modification is introduction of a theoretical corrective equation when the penetration is not performed vertically in order to isolate the skin friction that develops along the penetrating rod, which significantly affects DCP values. For this purpose, the torque moment is measured at various penetration depths by the same technique applied for the well-known Vane test. This corrective equation is then modified in light of the results obtained for validating in situ DCP tests.
It’s 10 o’Clock: Do You Know Where Your Sensors Are?
Authors: Stubstad Richard N. , Irwin Lynne H. , Lukanen Erland O. , Lawrence Clevenson M.
Published: April 2007

More than 400 falling weight deflectometer (FWD) devices are presently in use throughout the world, and deflection reading accuracy is very important. Deflections are measured in microns, or hundredths of a mil, and even very small errors in the deflection readings can have a profound effect on the results of backcalculation. One question that has somehow escaped scrutiny is the one alluded to in the title to this paper—exactly where along the deflection basin are the FWD deflection sensors positioned? This is an extremely important issue for proper definition of the deflection basin as a function of distance from the center of the loading plate. A review of the FWD load-deflection data in the Long Term Pavement Performance (LTPP) study found that in at least 7 percent of some 4 million lines of FWD deflection data in the National Information Management System (NIMS) database, the sensors were not positioned as reported. This problem is not limited to LTPP and NIMS, and it occurs all too frequently on FWDs everywhere. How sensor positioning errors influence backcalculated moduli, even if all other facets of the FWD data are 100 percent correct, is described. Examples of the errors found in NIMS are also presented—real-life illustrations of what can go wrong and how much influence these errors can have on pavement analysis. A method of scanning for sensor positioning errors without carrying out backcalculation is presented. By use of the suggested transform, sensor positioning errors are clearly evident when suspect data are compared with correct data along the same, or other, pavement sections.
Evaluating Measured Tire Contact Stresses to Predict Pavement Response and Performance
Authors: Roque Reynaldo , Ann Myers Leslie , Birgisson Bjorn
Published: April 2007

Recent research has indicated that measured contact stress distributions under radial truck tires are highly complex. These stress distributions help to explain near-surface distresses that have become more prevalent since the inception of radial tires, indicating that realistic contact stresses must be considered when pavement response and performance are evaluated. However, because of the complexities involved in measuring contact stresses under tires, obtaining these measurements directly on real pavements is not possible. Consequently, contact stress measurements have been made on systems having rigid foundations with embedded sensors. Therefore, determining whether tire contact stresses measured on a rigid foundation are significantly different from contact stresses under the same tire on an actual pavement is critical. Finite element analyses conducted indicated that both vertical and lateral tire contact stresses measured on rigid foundations accurately represent the contact stresses for the same tire on typical asphalt pavement structures. Some minor differences were observed for thin (50-mm surface) pavements on weak bases, but the correspondence in terms of both distribution and magnitude was still very good. The conclusion was that contact stresses measured by devices with rigid foundations appear to be suitable for predicting response and performance of highway pavements.
Rutting of Thin Pavements: Full-Scale Study
Authors: Ceratti Jorge A. , Núñez Washington P. , Gehling Wai Y.Y. , de Oliveira José A.
Published: April 2007

Since 1992, the Federal University of Rio Grande do Sul, along with the roads department of the same Brazilian state, has undertaken comprehensive research on weathered basalts, with the purpose of reducing the cost of low-volume pavements. Laboratory studies have led to a criterion (on the basis of the point load test) used to select deposits of these intensely fractured rocks. A traffic simulator was designed and built, and a pavement test facility was constructed on the university campus. A study was done of rutting of thin pavements on which weathered basalts were used as base layers. The traffic simulator applied more than 267,000 axle loads, ranging from 82 to 130 kN, on five full-scale test sections. Two different weathered basalts and three base thicknesses were used. A postmortem evaluation revealed that the base layer contributed the most to rutting. The axle load applications caused the pavement structure to settle and consolidate. A total of 4,148 measurements of rut depth, made at intervals, provided a statistically significant data set. Rutting evolution was shown to depend not only on traffic characteristics but also on pavement structure. With consideration of rutting as a major failure cause in thin pavements and a rut depth of 25 mm as a terminal criterion, load equivalence factors were calculated by means of a reliability analysis.
Super-Accelerated Testing of Flexible Pavement with Stationary Dynamic Deflectometer
Authors: Stokoe Kenneth H. , Bay James A. , Rosenblad Brent L. , Murphy Michael R. , Fults Kenneth W. , Chen Dar-Hao
Published: April 2007

The Texas Department of Transportation (TxDOT), in partnership with the Center for Transportation Research, has implemented the Texas mobile load simulator (TxMLS) as a tool for accelerated testing of in-service pavements. Although the TxMLS has been used successfully to test in-service pavements in the Yoakum and Fort Worth districts, the fact that only one TxMLS machine exists limits the number of accelerated pavement tests (APT) that can be performed. Therefore, TxDOT is evaluating a modification of the rolling dynamic deflectometer (RDD) for use as a super-accelerated pavement tester. In this application, the truck-mounted dynamic loading system is operated in a stationary mode, with the loading rollers and rolling sensors of the RDD removed from operation. The servohydraulic actuator is used for application of harmonic loading to a wheel footprint on the pavement surface. Hundreds of thousands of load repetitions are applied in a matter of hours; hence the designation as super-accelerated testing. This stationary dynamic deflectometer (SDD) is being studied as a possible tool for use in expanding TxDOT’s APT program. The SDD may allow TxDOT to increase, in a cost-effective manner, the number of accelerated tests that can be performed. Preliminary tests have been performed with the TxMLS and SDD on two different pavement recycling strategies constructed on the northbound and southbound lanes of US-281 in the Fort Worth District. That the same conclusion was reached about the relative performance of the test sections with both machines indicates the potential usefulness of the SDD.
Evaluating the Effectiveness of Norway’s “Speak Out!” Road Safety Campaign: The Logic of Causal Inference in Road Safety Evaluation Studies
Authors: Elvik Rune
Published: April 2007

The effects on road safety of the “Speak out!” road safety campaign are evaluated. The campaign, which began in Sogn og Fjordane County in Norway in 1993, is targeted toward teenagers and calls on car passengers to act as back-seat drivers and “Speak out!” to drivers about unsafe driving. The campaign’s effects were evaluated by means of two before-and-after studies and and a multivariate Poisson regression analysis. The results of these evaluation studies were very similar. The number of teenagers 16 to 19 years old who were killed or injured was reduced by about 10 percent; the number of occupants in this age group who were killed or injured was reduced by about 15 percent; and the number of car passengers who were killed or injured was reduced by about 30 percent. The number of killed or injured car drivers 16 to 19 years old did not change. Only the reduction among car passengers was statistically significant at the 10 percent level. It is nevertheless concluded that the “Speak out!” campaign has probably been effective in reducing the number of teenagers killed or injured in Sogn og Fjordane. This conclusion is based on a careful discussion of the logic of causal inference in nonexperimental evaluation research. Seven criteria are proposed for attributing causality to the relationship between a measure and changes in the dependent variable that the measure is intended to influence. The majority of these criteria were met in evaluations of the “Speak out!” campaign.
Coast-to-Coast Comparison of Time Use and Activity Patterns
Authors: Gangrade Sachin , Kasturirangan Krishnan , Pendyala Ram M.
Published: April 2007

Activity-based travel analysis has been gaining increasing attention in travel demand research during the past decade. Activity and trip information collected at the person level aids in understanding the underlying behavioral patterns of individuals and the interactions among their activities and trips. Activity and time use patterns across geographical contexts are compared. Such a comparison could shed light on the differences and similarities in travel behavior that exist between areas. To accomplish this objective, activity, travel, and time use information derived from surveys conducted in the San Francisco Bay and Miami areas has been analyzed to identify differences in activity engagement patterns across different sample groups. In general, it was found that activity and time use patterns are comparable across the two areas as long as the commuting status and demographic characteristics of the individuals are controlled for. In addition, the time-of-day distributions of various events such as wake-up time, sleeping time, time of departure and arrival at home, and work start and end times were compared. These events were considered important in defining the temporal constraints under which people exercise activity and travel choices. Once again, it was found that the distributions followed similar trends as long as the commuting status and the demographic characteristics of the individual were controlled for. However, there were noticeable differences that merit further investigation.
Mixed Generalized Linear Model for Estimating Household Trip Production
Authors: Lan Chang-Jen , Hu Patricia S.
Published: April 2007

An innovative modeling framework to estimate household trip rates using 1995 Nationwide Personal Transportation Survey data is presented. A generalized linear model with a mixture of negative binomial probability distribution functions was developed on the basis of characteristics observed from the empirical distribution of household daily trips. This model provides a more flexible framework and a better model specification for analyzing household-specific trip production behavior. Compared with traditional least squares-based regression models, the parameter estimates from the proposed model are more efficient. Although the mean accuracies from the two modeling approaches are comparable, the mixed generalized linear model is more robust in identifying outliers due to its unsymmetric prediction bounds derived from more correct model specification.
Are Travel Times and Distances to Work Greater for Residents of Poor Urban Neighborhoods?
Authors: Khattak Asad J. , Amerlynck Virginie J. , Quercia Roberto G.
Published: April 2007

The commuting patterns of low-income urban residents are discussed. On the basis of the spatial mismatch hypothesis, the question of whether central city low-income residents face an undue burden of commuting cost (time and distance) to work compared with the rest of the population is examined. Data from the 1995 Nationwide Personal Transportation Survey were used in the analysis. Models explaining travel time and distance to work are combined with a model explaining the probability of being employed on the basis of individual and neighborhood characteristics, thus correcting for sample selectivity. In general, it was found that urban residents are less likely to work than their suburban counterparts. Among the people who work, residents of low-income urban neighborhoods commute longer and farther than residents of low-income suburban neighborhoods. The average differences for the residents of the lowest-income neighborhoods are only 6 min and 2 mi (3 km). On the basis of the value of time, it is concluded that these national differences are not too large. The undue commute burden faced by residents of low-income neighborhoods may be shown to be a greater problem in some metropolitan areas than in others, suggesting further research at the metropolitan or regional level.
Period Effects and Cohort Effects in Life Cycles: Preliminary Analysis
Authors: Marker John T.
Published: April 2007

Travel behavioral data from five successive waves of the Puget Sound Transportation Panel were examined to determine whether period effects or cohort effects have a significant effect in life-cycle behavior. It was found that period and cohort effects may have a greater influence in household life-cycle models than previously believed. The results bring into question current methods using cross-sectional data analysis for life-cycle models, since predicted changes in activity behavior were not observed in households that made life-cycle transitions. The results are not conclusive, since other variables influencing activity behavior were not accounted for in the analysis.
Irregularly Sampled Transit Vehicles Used as Traffic Sensors
Authors: Elango Chandrasekar , Dailey Daniel J.
Published: April 2007

Performance monitoring is an issue of growing concern both nationally and in the state of Washington. Travel times and speeds always have been of interest to traveler information researchers, but there is limited infrastructure with which to collect such data on a continuous basis. Transit vehicles were used as probes, and a framework was developed for modeling the time series that arise from irregularly sampled transit vehicle locations. These samples of vehicle location were obtained from the King County Department of Metropolitan Services automatic vehicle location system. An optimal filter method that estimates speed as a function of space and time was developed. An optimal solution for the state vector, containing the variables speed and position, was made at each time step by using a Kalman filter.
Toronto Area Car Ownership Study: A Retrospective Interview and Its Applications
Authors: Roorda Matthew J. , Mohammadian Abolfazl , Miller Eric J.
Published: April 2007

Recent work in the area of comprehensive transportation modeling systems in a microsimulation framework, more specifically auto ownership modeling, has recognized the need for increased experimentation with dynamic models. Implicitly, dynamic models require longitudinal data. A Toronto area car ownership study was conducted to design and administer a longitudinal survey to fulfill the data requirements for such a dynamic model, to validate the survey results, and to conduct preliminary analysis on those results. An in-depth retrospective telephone survey was conducted with the help of a computer aid in Toronto, Canada. Simple univariate analyses were conducted on the data to determine the relationship between characteristics of the household and the occurrence of vehicle transactions, the choice of vehicle type, the duration a vehicle is held, and the degree of consumer loyalty to different types of vehicles.
Stabilization of a Vertical Tire Chip Embankment with Geogrids
Authors: Hsieh Chiwan , Wu Jeng
Published: April 2007

A research project that involves the construction of a full-size geogrid-reinforced test embankment was conducted. Waste tire chips were used as the lightweight backfill for the embankment. The joint research project involved participants from government agencies, academic research institutes, consulting firms, and material suppliers. To meet the function requirements, the north side of the embankment had to be built essentially as a vertical wall. To maintain stability, the vertical side of the embankment was reinforced with geogrids and covered with segmental retaining-wall facing. The objectives of the research study were to evaluate the feasibility of using waste tire chips as embankment backfill material when coupled with geogrid reinforcement and to evaluate the performance of various types of goesynthetic drainage products in the test embankment. To minimize settlement due to compression of the tire chips, various combinations of tire chips and soil mixtures or interlayers were used in the embankment construction. The details of the design and construction of the test embankment are described. Performance of the test embankment is evaluated based on available observation data.
Fine-Aggregate Angularity: Automated Image Analysis Approach
Authors: Masad Eyad , Button Joe W. , Papagiannakis Tom
Published: April 2007

Angularity is one of the important aggregate properties contributing to the permanent deformation resistance of asphalt mixtures. Therefore, methods that are able to rapidly and accurately describe aggregate angularity are valuable in the design process of asphalt mixtures. Two computer-automated procedures, which make use of the advances in digital-image processing, to quantify fine aggregate angularity, are presented. The first method relies on the concepts of the erosion-dilation techniques. This consists of subjecting the aggregate surface to a smoothing effect that causes the angularity elements to disappear from the image. Then, the area lost as a result of the smoothing effect is calculated and used to quantify angularity. The second method is based on the fractal approach. Image-analysis techniques are used to measure the fractal length of aggregate boundary. The fractal length increases with aggregate angularity. The proposed imaging techniques are used to capture the aggregate angularity of 23 sand samples that represent a wide range of materials. The results are compared with visual analysis and indirect methods of measuring fine-aggregate angularity, such as the uncompacted air voids, and the angle of internal friction of aggregate mass. In general, the results indicate much promise for measuring aggregate properties using automated imaging technologies.
European Research into Granular Material for Pavement Bases and Subbases
Authors: Dawson Andrew R. , Mundy Michael J. , Huhtala Matti
Published: April 2007

Two transnational European research projects in the area of granular materials for road pavements are described. The results are used to illustrate the state of practice as compared to the state of the art and are placed within the setting of a broad picture of national research within Europe. Discussed are the direction of European research, its implementation, those areas that will continue to be problematic, and the findings and strategies that suggest better-practice for non-European users. The use of the repeated-load triaxial test is shown to be an important aspect. Although the test is shown to have limitations for practical purposes, it illustrates the nature of material behavior that may be expected in situ. It is shown that a fundamental engineering understanding has been applied to granular material pavement layer technology but that there remain issues of in situ assessment, analytical methods, and variability of in situ conditions that hinder full application of current understanding.
Angular Parameter for Characterizing Road Surface Microtexture
Authors: Do Minh-Tan , Zahouani Hassan , Vargiolu Roberto
Published: April 2007

Development of a device for measuring road surface microtexture and the determination of a microtexture parameter related to wet road/tire friction are discussed. A laser autofocus system was selected from existing devices. The required characteristics were defined from consideration of the contact between wet roads and tires. The autofocus principle is presented briefly, and comparison is made with a tactile system. The microtexture parameter, called the theta parameter, is defined from the useful parts of the texture profiles, that is, those in contact with the tire. It characterizes relative positions of profile peaks. A simple method was proposed to define the peaks. The profile analysis program is presented briefly. Relevance of the theta parameter was validated on surfaces composed of coarse aggregates with planar exposed faces. The specimens were polished using a projection method to emphasize the microtexture contrast between surfaces. Friction was measured using a skid resistance tester (SRT) pendulum. Profiles were measured using both laser and tactile systems. Characteristics of profiles are given. The statistical distribution of theta values obtained on a profile may be described by an exponential function. Close agreement was found between theta values obtained from laser and tactile profiles, values from laser profiles being somewhat lower. The difference is attributed to profile length. Fair correlation was found ( r2 > 0.80) between theta values and SRT friction, and similar tendencies were observed from laser and tactile data.
Framework for the Analysis of Grocery Teleshopping
Authors: Marker John T. , Goulias Konstadinos
Published: April 2007

Household replenishment and consumer direct—two closely related and developing forms of teleshopping that are emerging as strategies within the broader realm of supply chain management—could have an impact on behavior related to grocery shopping trips, as well as on commercial development. In concept, household replenishment and consumer direct are the businesses of delivering groceries to households through various means. These grocery delivery systems have the potential to change household activity behavior, which could result in numerous changes throughout the transportation network. An examination of the relevant issues surrounding implementation of household replenishment and consumer direct, and an analysis of their potential impact on transportation systems planning, are provided. A conceptual framework for modeling changes in business and household behavior is also offered.
Enhanced Genetic Algorithm for Signal-Timing Optimization of Oversaturated Intersections
Authors: “Brian” Park Byungkyu , Messer Carroll J. , Urbanik Thomas
Published: April 2007

Enhancements were provided to a previously developed genetic algorithm (GA) for traffic signal optimization for oversaturated traffic conditions. A broader range of optimization strategies was provided to include modified delay minimization with a penalty function and throughput maximization. These were added to the initial delay minimization strategy and were further extended to cover all operating conditions. The enhanced program was evaluated at different intersection spacings. The optimization strategies were evaluated and compared with their counterpart from TRANSYT-7F, version 8.1. A microscopic stochastic simulation program, CORSIM, was used as the unbiased evaluator. Hypothesis testing indicated that the GA-based program with average delay minimization produced a superior signal-timing plan compared with those produced by other GA strategies and the TRANSYT-7F program in terms of queue time. It was also found from the experiments that TRANSYT-7F tended to select longer cycle lengths than the GA program to reduce random plus oversaturation delay.
North Carolina DOT’s Skill-Based Pay Program: A Working Model for Training and Compensating Highway Workers
Authors: Aschbrenner Donald R. , Domico Dan , Fountain Alvin M.
Published: April 2007

To meet the challenges of declining personnel resources, increased contract administration, and continuously increasing paved-road mileage, the North Carolina Department of Transportation (NCDOT) is developing flexibility and multiple skills in its approximately 4,050 employees classified as Transportation Workers. The department is the first North Carolina agency to implement such a program on a broad scale. A training and compensation system, known as Skill-Based Pay, helps all transportation workers develop job-related technical skills through structured training. The goal of the program is to create a workforce highly trained across various skill levels, keeping NCDOT competitive in the market. The program promotes flexibility and equity in broad, generic job classifications that meet employees’ and NCDOT’s training needs. This meshes well with the department’s Performance Management program, which encourages employees to acquire skills and rewards them when they do. The program is built on “skill blocks”—unique sets of tasks and duties selected as significant by each operating unit and categorized as entry, intermediate, journey, and advanced levels—each of which is worth a set dollar value. Each skill block is achieved through a four-step process: testing, on-the-job training, certification, and compensation. In this system, employees advance through the four levels but remain in the same broad class of Transportation Worker. The program has created enthusiasm among workers, and the workers drive the program.
The Operations and Maintenance Business Information Link: Information Technology for Performance Measurement
Authors: Sissom James D. , Compton Andy , Lichy David E.
Published: April 2007

The U.S. Army Corps of Engineers water resources management programs have undergone changes during the past two decades, including a shift in emphasis from the construction of new projects to the operation and maintenance (O&M) of existing projects. Consequently, expenditures for new construction have fallen while the O&M of existing projects has claimed an increasing share of the total agency budget. Given the current outlook of declining fiscal resources, Corps managers have recognized a need to evaluate the way the organization is doing business. The Corps O&M program appropriated approximately $1.7 billion for fiscal year 1999 to support an inventory of more than 4,000 projects. The program is managed through 8 division and 38 district offices across the nation. The Operations and Maintenance Business Information Link (OMBIL) integrates national program performance measurement, starting with criteria gathered at the lowest level, the local water resource project. The overall impact on the O&M program is twofold: Frontline employees contribute directly to corporate performance measurement, ensuring a national effort to achieve corporate goals and objectives, and the management hierarchy is able to support users at all levels through this outcome-oriented process. The result is a modified business methodology that enables more efficient and effective decision making.
Mechanistic Design Framework for Spalling Distress
Authors: Wang Ligang , Zollinger Dan G.
Published: April 2007

Spalling is a distress form in concrete pavements that often manifests as the breakdown of the joint of a slab within 15 cm (6 in.) of the joint or crack and can occur at both longitudinal and transverse joints. Efforts have been under way at Texas A&M University to formulate mechanistic spalling models derived from data gathered in recent Texas Department of Transportation studies related to spall development. Extensive field studies have led to the establishment of a spalling mechanism consisting of a step-by-step process that can be characterized with engineering mechanics. These findings indicate that spalling is the result of damage initiated in the form of a shear delamination that is oriented parallel to and at a shallow depth below the surface of the pavement. Conditions necessary for formation of the delaminations include low interfacial strength between the aggregate and mortar and sufficient evaporation of pore water from the hydrating concrete, resulting in differential drying shrinkage near the pavement surface. Delaminations have been noted to initiate early in the life of the pavement and, once formed, extend later into spalls as a result of incompressibles, freeze-thaw cycles, traffic loading, and other such effects. A design framework for delamination formation and subsequent spalling development is presented in a practical format in which to mechanistically design concrete pavement systems relative to spalling distress.
Top-Down Cracking in Washington State Asphalt Concrete Wearing Courses
Authors: Uhlmeyer Jeff S. , Willoughby Kim , Pierce Linda M. , Mahoney Joe P.
Published: April 2007

For years, pavement engineers within the Washington State Department of Transportation (WSDOT) have observed that longitudinal and fatigue (multiple-interconnected) cracks in their thicker asphalt concrete (AC) pavements appeared to crack from the top of the wearing course downward. Often, the cracks stop at the interface between the wearing course and the underlying bituminous layers (a depth of about 50 mm). Studies done elsewhere in the United States and internationally have reported similar results. The results of extensive coring that WSDOT routinely collects in its pavement rehabilitation process were compared in a study. WSDOT normally cores AC pavements to determine thickness for use in mechanistic-empirical design. In addition to coring for AC thickness, specific information noting surface-initiated (top-down) cracking with the crack depth or full-depth cracking was noted. WSDOT observed top-down cracking occurring in the thicker sections, with thinner sections cracking full depth. Top-down cracking generally started within 3 to 8 years of paving for pavement sections that were structurally adequate and were designed for adequate equivalent single-axle loads.
Cost-Effectiveness of Paving Fabrics Used to Control Reflective Cracking
Authors: Buttlar William G. , Bozkurt Diyar , Dempsey Barry J.
Published: April 2007

The Illinois Department of Transportation (IDOT) spends $2 million annually on reflective crack control treatments; however, the cost-effectiveness of these treatments had not been reliably determined. A recent study evaluated the cost-effectiveness of IDOT reflective crack control System A, which consists of a nonwoven polypropylene paving fabric, placed either in strips longitudinally over lane-widening joints or over the entire pavement (area treatment). The study was limited to projects constructed originally as rigid pavements and subsequently rehabilitated with one or more bituminous overlays. Performance of 52 projects across Illinois was assessed through crack mapping and from distress and serviceability data in IDOT’s condition rating survey database. Comparisons of measured reflective cracking in treated and control sections revealed that System A retarded longitudinal reflective widening crack development, but it did not significantly retard transverse reflective cracking, which agrees with earlier studies. However, both strip and area applications of these fabric treatments appeared to improve overall pavement serviceability, and they were estimated to increase rehabilitation life spans by 1.1 and 3.6 years, respectively. Reduction in life-cycle costs was estimated to be 4.4 and 6.2 percent when placed in medium and large quantities, respectively, and to be at a break-even level for small quantities. However, life-cycle benefits were found to be statistically insignificant. Limited permeability testing of field cores taken on severely distressed transverse joints suggested that waterproofing benefits could exist even after crack reflection. This was consistent with the observation that, although serviceability was generally improved with area treatment, crack reflection was not retarded relative to untreated areas.
Optimal Bus Stop Spacing Through Dynamic Programming and Geographic Modeling
Authors: Furth Peter G. , Rahbee Adam B.
Published: April 2007

A discrete approach was used to model the impacts of changing bus-stop spacing on a bus route. Among the impacts were delays to through riders, increased operating cost because of stopping delays, and shorter walking times perpendicular to the route. Every intersection along the route was treated as a candidate stop location. A simple geographic model was used to distribute the demand observed at existing stops to cross-streets and parallel streets in the route service area, resulting in a demand distribution that included concentrated and distributed demands. An efficient, dynamic programming algorithm was used to determine the optimal bus-stop locations. The model was compared with the continuum approach used in previous studies. A bus route in Boston was modeled, in which the optimal solution was an average stop spacing of 400 m (4 stops/mi), in sharp contrast to the existing average spacing of 200 m (8 stops/mi). The model may also be used to evaluate the impacts of adding, removing, or relocating selected stops.
Procedure to Evaluate Alternatives to Transit Bus Replacement
Authors: Khasnabis Snehamay , Naseer Mubashir
Published: April 2007

The addition of new buses to a transit agency’s fleet is a capital-intensive project. In an average year, more than 3,500 buses are purchased by FTA grantees. The annual cost of bus replacement easily exceeds $1 billion. A procedure to evaluate alternatives to bus replacement is presented. Two generic alternatives are identified—rehabilitation and remanufacturing. The former approach focuses on the repair of engines and machine components. The latter approach is to restore a vehicle’s structural integrity. The evaluation procedure is based on economic principles and quantifies the benefits and costs associated with postponing a bus replacement, either by rehabilitation or remanufacturing. A modified benefit-to-cost ratio (B/C) technique is proposed that incorporates intangible benefits and disbenefits, as well as a risk penalty associated with the extended use of an older bus. As an alternative to computing the B/C, the recommended approach is to estimate the maximum investment that can be justified in a rehabilitation or remanufacturing project using the derived benefits. An affordability index is developed that is sensitive to the risk penalty used. Numerous examples are presented to demonstrate the application of the proposed procedure. Finally, a set of guidelines is presented to assist transit agencies in determining the economic viability of postponing a new-bus purchase by rehabilitating or remanufacturing an older bus.
Attractiveness of Transportation Infrastructure Projects to Private-Sector Financing: Assessing the Hierarchical Analysis, Risk Scenario Method
Authors: Tsamboulas Dimitrios , Panou Konstanzinos , Abacoumkin Constantionos
Published: April 2007

A method to identify the attractiveness for private financing of a transport infrastructure project is presented. The objective of the method is to assist the public sector in identifying the attractiveness of a transportation infrastructure project for private financing, highlighting the factors that tend to reduce such attractiveness and providing the means to examine the viability of alternative risk-allocation scenarios related to risks undertaken by the state or private sector. The method allows for the simulation of the private sector’s attitude toward risk, employing practices of risk assessment in investments. Its innovation lies in how the whole process is structured so that participants understand beforehand whether an agreement can be concluded and which factors involved are critical. A key property of the method is the ease by which priorities of different risk components are synthesized into a hierarchical form through pairwise comparisons. This method, although targeted primarily for the public sector, could assist both private and public stakeholders investing in transport infrastructure projects (termed private-public partnerships) to reach an agreement. Basically, it is an interactive process characterized by the conflicting objectives and judgments of both public and private sectors.
Observed Traffic Pattern Changes Due to Variable Tolls
Authors: Burris Mark , Pietrzyk Michael C. , Swenson Chris R.
Published: April 2007

In August 1998 the Midpoint and Cape Coral Bridges in Lee County, Florida, began charging variable tolls based on the time of day. Traffic data collected at these two bridges are examined, including the number of vehicles, by transaction payment type and by time of day. These data were analyzed to determine if variable pricing toll discounts have changed traffic patterns at the toll bridges. Data collected from January through July 1998 (before the implementation of variable pricing) were compared to data collected from August through December 1998 (during variable pricing). The data were examined in both aggregate and half-hour time increments throughout the day. This allowed for initial analysis of ways that traffic volumes have shifted by time of day due to discounted tolls. Data were also collected on the payment methods of all bridge users. This information is critical, since only those users paying their toll electronically (approximately 23 percent of transactions) are eligible for the variable pricing toll discounts. Therefore, two groups were examined separately—eligible users (the test group) and ineligible users (the control group). Variable pricing was found to have caused significant changes in the travel behavior of eligible users. On the Cape Coral and Midpoint Bridges, the number of eligible users increased significantly during the discount periods and decreased significantly during the peak periods. In contrast, changes in the traffic patterns of ineligible users were found to be statistically insignificant.
Estimating Road User Costs Associated with Highway Construction Projects: Simplified Method
Authors: Daniels Ginger , Stockton William R. , Hundley Robert
Published: April 2007

Road user costs (RUC) are defined as the estimated incremental daily costs to the traveling public resulting from the construction work being performed. Those costs are primarily time lost because of conditions such as detours/rerouting that add to travel time, reduced roadway capacity that slows travel speed and increases travel time, or a delay in the opening of a new or improved facility that prevents users from gaining travel time benefits. In Texas, RUC analyses and associated liquidated damages have been applied predominantly to high-profile urban freeway reconstruction projects, which are ideal candidates for RUC application because of the potential for very high motorist delay costs. A much wider range of projects involving the addition of capacity can be considered for RUC. Not all potential projects, however, are as complicated as urban freeway reconstruction efforts that require detailed simulation modeling to determine the value of RUC. The results of a research study that developed a manual technique for determining RUC are documented, along with associated liquidated damages for typical added-capacity and highway rehabilitation projects. The technique involves a series of look-up tables that provide RUC values on the basis of project type and a minimal number of project attributes. Two different approaches were employed: a before-and-after approach for added capacity projects and a during-versus-after-construction approach for rehabilitation projects.
Genetic Algorithm for a Pickup and Delivery Problem with Time Windows
Authors: Jung Soojung , Haghani Ali
Published: April 2007

A mathematical model for a multivehicle pickup and delivery problem with time windows is presented, and a genetic algorithm (GA) for solving it is proposed. The mathematical model is formulated as a mixedinteger linear programming problem. The objective of the proposed model is to minimize the total cost, which consists of the fixed cost for the vehicles, the routing cost, and the customer inconvenience cost, which is modeled as a penalty cost for violation of the time windows of each customer. Like other combinatorial problems, solving this pickup and delivery problem is time-consuming, and sometimes it is impossible to find an exact solution. The problem is solved exactly for up to six demands (12 nodes), and GA is used for larger problems with more than six demands. The proposed GA can solve a pickup and delivery problem in an extremely short time compared with the exact solution procedure. It also produces excellent results for small problems. A GA used to solve a 30-demands problem (60 nodes) with 10 vehicles is illustrated.
Competition and Equilibria of Private Toll Roads in a Traffic Network
Authors: Yang Hai , Kin Woo Ka
Published: April 2007

The equilibria based on a situation in which two or more profitmaximizing private firms operate multiple toll roads in a road network are examined. The profits are interrelated because of demand interdependence in the network. A competitive game model is developed to analyze the strategic interactions between the private toll road operators in determining their supply (road capacity) and price (toll level) over the network. A simple but representative case of two competitive firms, each providing a single toll road (corresponding to a single link) on the network, is considered in which the two toll roads are either substitutable or complementary in terms of their demand interdependence. A quasi-Newton method in conjunction with a sensitivity analysis method of equilibrium network flow is used to determine the competitive game solutions subject to network equilibrium constraints.
Dynamic Traffic Assignment in Design and Evaluation of High-Occupancy Toll Lanes
Authors: Abdelghany Ahmed F. , Abdelghany Khaled F. , Mahmassani Hani S. , Murray Pamela M.
Published: April 2007

Application of a dynamic traffic assignment-simulation methodology to the analysis and evaluation of network performance under various schemes for the design and operation of high-occupancy toll (HOT) lanes is described. The DYNASMART traffic simulation-assignment model, which combines the ability to simulate traffic flow and to represent dynamic route choice behavior, is used to model the problem. Different dimensions for the design and operation of HOT lanes are considered in this study, including ( a) lane utilization in terms of adding a new lane or using an existing lane of the facility as a HOT lane; ( b) physical separation of the HOT lane in terms of access point frequency; ( c) access restriction based on vehicle occupancy; ( d) HOT lane pricing structure, which may be fixed or congestion dependent; and ( e) different demand levels with different percentages of high-occupancy vehicles (HOV). A set of experiments was designed to compare the performance of the HOT lanes and the total network under these different operating characteristics. A network in Texas that represents the south central part of the Fort Worth area is used in these experiments. The results were analyzed under each of these different operating characteristics, yielding useful insights for the design and evaluation of HOT lanes.
Evaluation of Pennsylvania Road Safety Audit Pilot Program
Authors: Pietrucha Martin T. , Pieples Timothy R. , Garvey Philip M.
Published: April 2007

Historically, highway safety countermeasures have been developed in response to accidents. These countermeasures are based on the identification of contributing factors in the system operating environment that can be eliminated or changed so that the accidents caused by them will no longer occur. The road safety audit is a process whereby a team of experts attempts to identify features of the highway operating environment that could be potentially dangerous and then works to eliminate or change these features during the different phases of design before the system becomes operational. The Pennsylvania Department of Transportation (PennDOT) is interested in formulating a safety audit process for use on roads in the state. In cooperation with PennDOT, the Pennsylvania Transportation Institute conducted research on the application of a road safety audit process in two PennDOT districts.