bluuebunny/crossref_metadata_2025 huggingface dataset:
Commuter Bicyclist Route Choice: Analysis Using a Stated Preference Survey
Authors: Stinson Monique A. , Bhat Chandra R.
Published: April 2007

The importance of factors affecting commuter bicyclists’ route choices was evaluated. Both route-level (e.g., travel time) and link-level (e.g., pavement quality) factors are examined. Empirical models are estimated using data from a stated preference survey conducted via the Internet. The models indicate that, for commuter bicyclists, travel time is the most important factor in choosing a route. Presence of a bicycle facility (especially a bike lane or separate path), the level of automobile traffic, pavement or riding surface quality, and presence of a bicycle facility on a bridge are also very important determinants. Furthermore, there are policy implications of these results for bicycle facility planning.
Bicycle Commuting and Facilities in Major U.S. Cities: If You Build Them, Commuters Will Use Them
Authors: Dill Jennifer , Carr Theresa
Published: April 2007

Some surveys indicate that providing bicycle lanes and paths may encourage more people to commute by bicycle. The presence of a striped lane or separated path can increase a cyclist’s perception of safety. With growing concerns over traffic congestion and vehicle pollution, public policy makers are increasingly promoting bicycling as an alternative for commuting and other utilitarian trip purposes. State and local spending on bicycle facilities has increased significantly over the past decade. Previous studies have linked higher levels of bicycle commuting to various demographic and geographic variables. At least one analysis showed that cities with higher levels of bicycle infrastructure (lanes and paths) witnessed higher levels of bicycle commuting. Research was conducted that affirms that finding by analyzing data from 43 large cities across the United States. This cross-sectional analysis improves on previous research by including a larger sample of cities, not including predominantly college towns, and using consistent data from the Bureau of the Census 2000 Supplemental Survey. Although the analysis has limitations, it does support the assertion that new bicycle lanes in large cities will be used by commuters.
Development of Bicycle Compatibility Index for Rural Roads in Nebraska
Authors: Jones Elizabeth G. , Carlson Timothy D.
Published: April 2007

The development of a rural bicycle compatibility index (RBCI) is described. A recent FHWA research project developed a Bicycle Compatibility Index (BCI). This index was developed for urban and suburban roadway segments, and it incorporated those variables that bicyclists typically use to assess how compatible a roadway segment is for travel by bicycle. The FHWA BCI can be used by bicycle coordinators, transportation planners, traffic engineers, and others to evaluate existing facilities. With it, they can determine what improvements may be required, as well as the geometric and operational requirements for new facilities to achieve the desired level of bicycle service. No such tool exists for the rating of rural roadway segments, however. There was work done to develop a rural equivalent of the BCI. Roadways in rural Nebraska were used to develop the RBCI. Although the specific results of this work are clearly applicable to Nebraska and other similar rural areas, the general methodology and concepts could easily be used to develop a more general RBCI that would have national applicability. An RBCI will provide bicycle coordinators, transportation planners, traffic engineers, and others with the capability to better plan and design bicycle-compatible roadways. Specifically, an RBCI model can be used for operational evaluation, design, and planning.
Time-Temperature Superposition and Physical Hardening Effects in Low-Temperature Asphalt Binder Grading
Authors: Basu Arindam , Marasteanu Mihai O. , Hesp Simon A. M.
Published: April 2007

During the development of the Strategic Highway Research Program low-temperature binder specifications, in an effort to propose practical laboratory tests that require less time to perform, the time–temperature superposition principle was used to show that the stiffness after 2 h of loading at the performance-graded (PG) low temperature can be approximated by the stiffness after 60 s of loading at 10°C above the PG low temperature. This equivalence principle was developed on the basis of test results from the eight core asphalts and is widely accepted today. However, actual 2-h tests were not performed to experimentally validate this equivalence. Furthermore, the effect of physical hardening on time–temperature superposition was not considered. The validity of the time–temperature equivalence factor used in the low-temperature specification criterion and the ways in which the deviations could affect the current specification are evaluated.
Do Asphalt Mixtures Correlate Better with Mastics or Binders in Evaluating Permanent Deformation?
Authors: Shenoy Aroon , Stuart Kevin , Mogawer Walaa
Published: April 2007

Researchers have often looked for relationships between mechanical properties of asphalt mixtures and rheological properties of binders when assessing the resistance of mixtures and binders to permanent deformation. When mixtures are subjected to deformation on application of a stress, aggregates act as load-bearing entities, and binders deform in response to applied stress. Intuitively, a correlation must exist between the properties of mixtures and binders. However, a good correlation usually is not observed. There could be a number of reasons for the observed poor correlations, including ( a) variability in the data or a possible change in the microstructure of two-phase, polymer-modified asphalt in the presence of aggregates, or ( b) strong interactions between the aggregate and the binder that, of course, are not reflected in the binder properties. In such cases, there are reasons to believe asphalt mastics might provide a better correlation because they would account for at least the physicochemical aspects of the aggregate–binder interaction. The present work compared asphalt mixture data initially with mastic data and then separately with binder data. The mastic and binder rheological data were generated with the same equipment under identical conditions of measurement to identify which one correlates better with the mixture data. A good correlation was obtained in only one case when Superpave® shear tester data for mixtures were compared with the dynamic shear rheometer data for binders. In all cases analyzed in this work, no correlation was found between the permanent deformation for mixtures and the rheological properties of the mastics.
Creep Compliance of Polymer-Modified Asphalt, Asphalt Mastic, and Hot-Mix Asphalt
Authors: Vacin Ota , Stastna Jiri , Zanzotto Ludo
Published: April 2007

The possibility of using commercial rheometers for comprehensive testing of asphalt binders, asphalt mastics, and hot-mix asphalts (HMA) is explored. Samples of one polymer-modified asphalt, its mix with fine mineral filler (mastic), and one HMA prepared with the same modified asphalt as binders were tested in the dynamic shear rheometer (DSR) and the bending beam rheometer (BBR). All tested materials can be characterized by their discrete relaxation and retardation spectra (under the condition of small deformations). DSR testing was performed in the plate–plate and the torsion bar geometry. From the obtained relaxation and retardation spectra, the shear compliance, J(t), was calculated and compared with the tensile creep compliance, D(t), measured in BBR (both creep and recovery experiments were run). A simple relationship between J(t) and D(t) was found for the asphalt binder and the asphalt mastic. In the case of HMA, the bulk compliance, B(t), contributes to D(t) at short and long times. Both the Boltzmann superposition principle and the time–temperature superposition principle hold very well for all tested materials at low temperatures. There are qualitative differences, in the rheological behavior, of the asphalt binder and asphalt mastic on one side and the HMA on the other. These differences can be seen in dynamic (DSR) as well as in transient (BBR) experiments.
Field Evaluation of Asphalt Additives to Control Rutting and Cracking
Authors: McDaniel Rebecca S. , Bahia Hussain U.
Published: April 2007

The performance of a variety of materials added to asphalt binders and mixtures to change their properties, particularly with respect to rutting and cracking, was investigated. Two approaches were taken. The first was a field trial of seven modifiers. The modifiers evaluated included plastomers, elastomers, chemical modifiers, and particulates. The second approach was a laboratory study of the effects of these modifiers on binder and mixture properties. The field trial showed that modifiers are not essential to ensure that the pavement will not rut; none of the mixtures evaluated here exhibited appreciable rutting. Dramatic differences were noted in the cracking behavior, however. The newly developed MP-la binder tests were able to identify binders that were more prone to cracking.
Improving Traffic Safety: A New Systems Approach
Authors: Zein Sany R. , Navin Francis P. D.
Published: April 2007

A guiding principle of modern traffic safety professionals attempting to reduce the risks associated with traffic is to holistically address traffic safety as a multidisciplinary partnership issue. The systems approach focuses on the relationships and dependencies between the various elements of the traffic system. The C3-R3 Systems Approach to traffic safety is introduced; the building blocks of the C3-R3 approach are three entities (the road user, the vehicle, and the road environment), three pre-crash timeline phases (creation, cultivation, and conduct), and three postcrash timeline phases (response, recovery, and reflection). This approach is proposed as a framework for multidisciplinary traffic safety professionals to research traffic safety issues in an integrated, systematic manner. The C3-R3 approach provides an enhanced systematic framework that more clearly identifies the stages at which traffic safety professionals can intervene to promote road safety. The graphical representation of the C3-R3 system, as presented, emphasizes the convergence of the entities as the timeline proceeds toward a crash event and their subsequent redivergence in the postcrash timeline. Every combination of entity and timeline phase represents a cell in the C3-R3 system; the contents of each cell represent the individual elements that traffic safety professionals need to focus on and understand in order to reduce the crash risk. The C3-R3 Systems Approach represents a starting point to encapsulate the systems approach concepts in traffic safety. It is expected that as more professionals adopt systems thinking, the C3-R3 approach will continue to evolve, expand, and improve.
Restraint Use and Age and Sex Characteristics of Persons Involved in Fatal Motor Vehicle Crashes
Authors: Lee Brian Ho-Yin , Schofer Joseph L.
Published: April 2007

The lap and shoulder belt combination can reduce the risk of fatal motor vehicle crash injuries to front-seat occupants by 45% and the risk of moderate-to-critical injuries by 50%. The significant life- and cost-saving potentials of these restraining devices, installed in virtually every vehicle in the United States, are well recognized, but the benefits come only from their actual use. Identified are two demographic characteristics of unrestrained persons involved in fatal crashes, age and sex, to provide a basis for targeting educational and promotional efforts to encourage restraint use among the most vulnerable groups. Analyses are based on 1996 to 2000 crash data from the Fatality Analysis Reporting System, compared with exposure data from the 1995 Nationwide Personal Transportation Survey. This study found that the risk of sustaining fatal injuries in a vehicle crash is reduced by 54% when occupant restraints are used. A much higher proportion of young males in the 16 to 19 and 20 to 24 age groups involved in fatal crashes do not use restraints, about 1.72 and 1.69 times greater, respectively, than those who do use restraints. While females in these age groups are also overrepre-sented, the extent of this excess is less than that of males. This underscores the need to find ways to educate young people, especially young males, about the benefits of restraint use.
Explicit Modeling of Joint Travel by Household Members: Statistical Evidence and Applied Approach
Authors: Vovsha Peter , Petersen Eric , Donnelly Robert
Published: April 2007

A substantial portion of regional travel is implemented by household members who travel together, primarily to participate in a shared household activity. Joint household travel is not explicitly accounted for in most regional travel models in which the unit of travel (either trip or tour) is considered for each person separately at each modeling stage—generation, mode, destination, and time-of-day choice. In addition, statistical evidence demonstrates that the vast majority of shared-ride travel consists of joint household travel. A modeling approach that distinguishes shared activity-based joint household travel from arranged interhouse-hold carpooling is clearly desirable to support accurate forecasts of shared-ride travel, critical in the evaluation of high-occupancy vehicle lanes or the adoption of toll strategies differentiated by occupancy levels. A range of aspects of joint travel both with empirical evidence and with discussion of modeling issues are addressed. A set of joint travel models is presented that has been estimated with the mid-Ohio regional travel household-interview survey. The model reported is one of the innovative components of the tour-based travel demand modeling system that has been developed for the Mid-Ohio Regional Planning Commission.
Dynamic Origin-Destination Demand Estimation with Multiday Link Traffic Counts for Planning Applications
Authors: Zhou Xuesong , Qin Xiao , Mahmassani Hani S.
Published: April 2007

A dynamic origin–destination demand estimation model for planning applications with real-time link counts from multiple days is presented. Based on an iterative bilevel estimation framework, the upper-level problem is to minimize both the deviation between estimated link flows and real-time link counts and the deviation between estimated time-dependent demand and given historical static demand. These two types of deviations are combined into a weighted objective function, where the weighting value is determined by an interactive approach to obtain the best compromise solution. The single-day formulation is further extended to use link counts from multiple days to estimate the variation in traffic demand over multiple days. A case study based on the Irvine test bed network is conducted to illustrate the methodology and estimate day-to-day demand patterns. The application illustrates considerable benefits in analyzing the demand dynamics with multiday data.
Modeling Departure Time Choice in the Context of Activity Scheduling Behavior
Authors: Ettema Dick , Timmermans Harry
Published: April 2007

Development of a model of departure choice behavior in the context of activity-travel scheduling behavior is reported. Based on a brief characterization of the literature, some key properties of the desired model are identified. Then, the theoretical framework is outlined and an operational model is derived. Next, the model is estimated with activity-travel diary data, collected in the context of the Albatross model system. The results are promising. Avenues of future research are discussed.
Day-to-Day Evolution of Network Flows Under Departure Time Dynamics in Commuter Decisions
Authors: Srinivasan Karthik K. , Guo Zhiyong
Published: April 2007

Day-to-day dynamics in an urban traffic network induced by departure time dynamics in commuter decisions are investigated. This investigation relaxes some key restrictions about fixed departure time and equilibrium assumptions to analyze the stability and performance of urban traffic networks over a multiple day planning horizon. A simulation-based framework is developed to analyze day-to-day dynamics by integrating an empirically calibrated model of dynamic departure time decisions with a dynamic network assignment model. Computational experiments are used to investigate the effect of the following experimental factors: recurrent network congestion level, time-dependent loading profile, and users’ sensitivity to commute experience and trip-time volatility on network performance and reliability. The findings provide evidence of considerable day-to-day variations and stochasticity in network flows and performance, even under the assumption of fixed routes and in the absence of information. The results indicate that ( a) the network performance under departure time dynamics can deviate significantly from equilibrium; ( b) the departure time adjustment process is remarkably stable and reaches stationarity, although the departure time choices do not appear to be at equilibrium; ( c) departure time dynamics introduce significant volatility in trip times from day to day; and ( d) increasing the sensitivity of users to commute and network performance attributes (schedule delay, trip-time variability) can lead to more stable system behavior and reliability. These results have important implications for estimation of time-dependent origin–destination matrices, dynamic network analysis, and effective congestion management strategies.
Dynamic Modeling of Household Automobile Transactions
Authors: Mohammadian Abolfazl , Miller Eric J.
Published: April 2007

Automobiles play a pivotal role in daily life, which makes them a subject of interest in many academic fields. Transportation planners are interested in knowing how many and what types of automobiles are owned by households, how people adjust their fleet, and how they use their vehicles. The primary objective of this study was to develop a comprehensive dynamic model of household automobile transactions at a disaggregate level to be used in a dynamic microsimulation modeling framework that can provide a direct forecast of consumer demand for personal-use vehicles. A market-based decision-making process and a transaction approach were applied for this project because of their consistency with the actual processes followed by decision makers. In the proposed framework, each year a decision maker faces four choices: add a new vehicle to the fleet, dispose of one vehicle, trade one of the vehicles in the fleet, or do nothing. A mixed (random parameters) logit model was used to investigate the effects of heterogeneity in the dynamic transaction model and distinguish between heterogeneity- and state-dependence-based explanations for the observed persistence in choice behavior. In this study, the application of dynamic variables representing the occurrence of changes in household state and their impacts on the observed behavior were also investigated.
Prototype Model of Household Activity-Travel Scheduling
Authors: Miller Eric J. , Roorda Matthew J.
Published: April 2007

The Toronto Area Scheduling Model for Household Agents (TASHA), a new prototype activity scheduling microsimulation model, generates activity schedules and travel patterns for a 24-h typical weekday for all persons in a household. The prototype model is based solely on conventional trip diary data and therefore is applicable in many urban areas where activity data may not be available. The model makes use of the concept of the project, a "container" of activities with a common goal, to organize activity episodes into the schedules of persons in a household. A heuristic, or rule-based, method is used to organize activities into projects and then to form schedules for interacting household members. The TASHA model is considered to be a successful first attempt to operationalize a generalized conceptual model of household decision making, with reasonable correspondence between model and observed trip rates and chain characteristics.
Effects of Less-Equilibrated Data on Travel Choice Model Estimation
Authors: Oh Jun-Seok , Cortés Cristián E. , Recker Will
Published: April 2007

Most discrete choice models assume steady state conditions and a fully equilibrated system when estimating unknown coefficients from real-world data. However, the estimated model can be biased when the data set used for the model estimation was drawn from non- or less-equilibrated traveler behavior. The resulting biased model could lead to a misunderstanding of the system. Such effects on discrete choice model estimation were examined by performing Monte Carlo simulation experiments. A day-to-day dynamic evolutionary framework was used to observe changes in traveler’s choice and to compare the estimated results during the adjustment process with the true behavior parameters.
Projecting Incidence and Costs of Sprawl in the United States
Authors: Burchell Robert W. , Galley Catherine C.
Published: April 2007

The purpose of this research is to project historical national development patterns (sprawl, or uncontrolled growth) into the future and measure the impacts of this development compared with a more controlled development future. The costs of sprawl are calculated from 25-year growth projections in which resulting impacts are recorded in each of 3,100 counties nationwide. Unique regional definitions of urban, suburban, rural, and undeveloped counties are formulated according to density and prior levels of development. Then sprawl is defined as significant residential and nonresidential development in rural and undeveloped counties. Sprawl is subsequently controlled both within a region and within a county to contain growth in the most developed portions of each, using the equivalent of urban growth boundaries at the regional level and urban service areas at the county level. A future with and without controls generates the differences in development in particular locations. Differences in counties with respect to land conversion rates, road development requirements, housing unit mix and costs, and public-service availability and costs determine growth impacts under the two scenarios. The difference between the two analyses provides empirical evidence of the likely impact of a future with sprawl as opposed to one in which it is reduced.
Regional Land Use and Transportation Planning with a Genetic Algorithm
Authors: Balling Richard , Lowry Michael , Saito Mitsuru
Published: April 2007

A new approach to regional land use and transportation planning, which uses a genetic algorithm as an integrated optimization tool, is presented. The approach is illustrated by applying it to the Wasatch Front Metropolitan Region, which consists of four counties in the state of Utah. This genetic algorithm–-based approach was applied earlier to the twin cities of Provo and Orem in Utah, but here it is adapted to regional planning. Three issues make regional planning particularly difficult: ( a) individual cities have significant planning autonomy, ( b) the search space of possible plans is immense, and ( c) preferences between competing objectives vary among stakeholders. The approach used here addresses the first issue by the way the problem is formulated. The second issue is addressed with a genetic algorithm. Such algorithms are particularly well suited to problems with large search spaces. The third issue is addressed by using a multiobjective fitness function in the genetic algorithm. It was found that a genetic algorithm could produce a set of nondominated future land use scenarios and street plans for a region, from which regional planners can make a selection. Execution of the algorithm to produce 100 plans per generation for 100 generations took about 4 days with a high-end personal computer. Interesting trends for reducing change and traffic congestion were discovered.
Propagation of Uncertainty in Transportation Land Use Models: Investigation of DRAM-EMPAL and UTPP Predictions in Austin, Texas
Authors: Krishnamurthy Sriram , Kockelman Kara Maria
Published: April 2007

Propagation of uncertainty in outputs of a standard integrated model of transportation and land use has been examined. Austin-calibrated DRAM-EMPAL predictions of residence and work locations were used as inputs to a UTPP-type four-step travel demand model, and the resulting travel times were fed forward into the future period’s land use models. Covariance in inputs (including model parameters and demographic variables) was accommodated through multivariate Monte Carlo sampling of 200 scenarios. Variances in land use and travel predictions were analyzed over time and as a function of input values. Results indicate that output variations were most sensitive to the exponent of the link performance function, the split of trips between peak and off-peak, and several trip generation and attraction rates. Twenty years in the future, final uncertainty levels (as measured by coefficients of variation) solely due to input and parameter estimation errors are on the order of 38% for total regional peak-period vehicle miles traveled (VMT), 45% for peak-period flows, and 50% and 37% for residential and employment densities, respectively. This means central point estimates of key model outputs are very likely (>30%) to fall 38% to 50% below or above the mean value. In the Austin example, 15% of the region’s 200 simulated peak-period VMT estimates fell below 3.7 million mi per day and 15% exceeded 8.4 million mi. Such substantial variation is solely due to standard model parameter and input uncertainties. Other uncertainty about the future and about human behavior exists and will add more variation.
Evaluation of Moisture Sensitivity and Performance of Lime in Hot-Mix Asphalt: Resilient Modulus, Tensile Strength, and Simple Shear Tests
Authors: McCann Martin , Sebaaly Peter E.
Published: April 2007

The use of hydrated lime in hot-mix asphalt (HMA) is an accepted practice for many state highway departments. However, there are various techniques of introducing lime into the mixture and several factors that favor one method over another. The goal of this study was to evaluate the mechanical properties of lime-treated HMA mixtures before and after multiple cycles of freeze–thaw moisture conditioning. The mechanical tests measured the resilient modulus, tensile strength, and simple shear. In addition, the three test procedures were compared for evaluating the moisture sensitivity of HMA mixtures. With the addition of lime and after multiple cycles of freeze–thaw moisture conditioning, all mixtures demonstrated an enhanced ability to retain the original measured properties. The four methods of lime treatment—dry lime to moist aggregates, lime slurry to dry aggregates, and either a 48-h marination time or no marination time—were found to be statistically equivalent. The evaluation of moisture sensitivity of an HMA mixture is possible with all three mechanical test procedures. Resilient modulus proved to be the best technique for measuring small reductions in strength. When the loss of strength due to moisture sensitivity exceeded 20%, the measurement of tensile strength provided a better statistical correlation.
Louisiana Experience with Foamed Recycled Asphalt Pavement Base Materials
Authors: Mohammad Louay N. , Abu-Farsakh Murad Y. , Wu Zhong , Abadie Chris
Published: April 2007

Utilization of existing recyclable materials has always been key to more efficient and economical highway construction. Use of the foamed-asphalt (FA) technique to stabilize recycled asphalt pavement (RAP) is one strategy for an efficient use of salvaged construction materials. The main objective of this study is to investigate the potential use of FA-treated RAP as a base course material in lieu of a crushed-limestone base beneath a concrete pavement layer. Test sections were constructed at US-190 near Baton Rouge, Louisiana, and used for field evaluation of the FA RAP base. The laboratory mixture design of the FA RAP, the construction of the experimental base section, and the field evaluation of the stiffness of the FA RAP base layers using different in situ testing devices are presented. Preliminary results of both laboratory and field tests showed that the FA-treated RAP mixtures are very promising and can be used as an alternative to the traditional limestone base beneath a concrete pavement layer.
Use of Screenings to Produce Hot-Mix Asphalt Mixtures
Authors: Allen Cooley L. , Zhang Jingna , Huner Michael H. , Ray Brown E.
Published: April 2007

Thin-lift hot-mix asphalt (HMA) layers are utilized in almost every maintenance and rehabilitation application. These mix types require smaller maximum particle sizes than do most conventional HMA surface layers. Although the primary functions of thin-lift HMA are to level the pavement surface, smooth the surface, or slow the deterioration of the existing pavement, or all three, these mixes may also provide some structural improvement, depending on the layer thickness placed. The use of manufactured aggregate screenings (fine aggregate stockpiles) as the sole aggregate portion of an HMA mixture was evaluated in this study. Mixes of this nature have the potential for use as thin-lift HMA layers. Two different sources of aggregate screenings, granite and limestone, were utilized to design mixtures at varying design air void contents and then tested for rut susceptibility. The use of a neat versus a modified asphalt binder was also evaluated, as well as the potential advantages of cellulose fiber additives. These mixtures using 100% manufactured screenings proved to be acceptable with regard to rutting resistance. No work was performed in this study to examine thermal cracking or durability.
Refinement of New-Generation Open-Graded Friction Course Mix Design
Authors: Watson Donald E. , Ann Moore Kathryn , Williams Kevin , Allen Cooley L.
Published: April 2007

Open-graded friction course (OGFC) has been used in the United States for more than 50 years. In 2000, National Center for Asphalt Technology (NCAT) research led to a recommended mix design procedure for a new-generation OGFC, but the work involved only one aggregate source. Therefore, NCAT is in the process of refining this design procedure to ensure that it is applicable to other aggregate types used in surface mixes throughout the United States. The objectives of NCAT's current research are to refine and field validate the new-generation OGFC mix design procedure. This work has led to several experiments. Several objectives have been identified that need to be addressed. Superpave® technology and use of the Superpave gyratory compactor (SGC) need to be incorporated into the mix design procedure. The Cantabro test for durability and resistance to stone loss needs to be adapted to SGC-prepared specimens and performance parameters established. The asphalt draindown test (AASHTO T 305-97), which was developed for stone-matrix asphalt mixtures, also needs to be evaluated for applicability to OGFC mixtures. In addition, a method for effectively evaluating air void criteria needs to be investigated. On the basis of the research conducted in this study, 50 gyrations of the SGC was selected as the design compactive effort during mix design. Also, the use of SGC-prepared samples during the Cantabro test appears to be a reasonable alternative to use of Marshall-compacted samples.
Development of Efficient Crack Growth Simulator Based on Hot-Mix Asphalt Fracture Mechanics
Authors: Sangpetngam Boonchai , Birgisson Bjorn , Roque Reynaldo
Published: April 2007

It has long been accepted that cracking of hot-mix asphalt (HMA) pavements is a major mode of premature failure. Many state departments of transportation have verified that pavement cracking occurred not only in fatigue cracking in which a crack initiates from the bottom of the asphalt layer but also in other modes such as low-temperature cracking and the more recently identified top-down cracking. Recent work at the University of Florida has led to the development of a crack growth law based on viscoelastic fracture mechanics that is capable of fully describing both initiation and propagation of cracks in asphalt mixtures. The model requires the determination of only four fundamental mixture parameters, which can be obtained from less than 1 h of testing using the Superpave® indirect tensile test (IDT). These parameters can account for microdamage, crack propagation, and healing for stated loading conditions, temperatures, and rest periods. The generalization of the HMA crack growth law needed for its successful implementation into a displacement discontinuity boundary element method is described. The resulting HMA boundary element approach is shown to predict the crack propagation of two coarse-graded mixtures under cyclic IDT loading conditions.
Application of Weibull Theory in Prediction of Asphalt Concrete Fatigue Performance
Authors: Tsai Bor-Wen , Harvey John T. , Monismith Carl L.
Published: April 2007

The objectives are to present the feasibility of utilizing the Weibull proportional hazards (PH) model and the Weibull accelerated failure time model of survival analysis to predict in situ pavement fatigue performance from laboratory fatigue test results. A set of WesTrack temperature sensitivity fatigue tests is used as an example to demonstrate how the Weibull PH model works. An example utilizing the deflection data from a heavy vehicle simulator test is given to verify the feasibility of the failure time model. The relationship between mode factor and controlled-deformation fatigue test is discussed using the same example. The Weibull theory approach has potential for use in recursive mechanistic-empirical design procedures.
Precision of Shear Tests in Evaluating Asphalt Mixtures
Authors: Michael Anderson R. , Steger Richard K. , Huber Gerald A. , Romero Pedro
Published: April 2007

Various methods exist to measure the mechanical properties of hot-mix asphalt (HMA). To be useful such a test not only must measure a property that controls performance but also must be repeatable. The Strategic Highway Research Program developed tests with the Superpave® shear tester that have been shown to be related to HMA performance. To date, repeatability has not been quantified. The results of a repeatability study for the measurement of shear stiffness (frequency sweep) and of permanent shear strain (repeated-load, constant-height testing) are reported.
Model Mobile Load Simulator Testing at National Center for Asphalt Technology Test Track
Authors: de Fortier Smit André , Hugo Fred , Rand Dale , Powell Buzz
Published: April 2007

One-third-scale model mobile load simulator (MMLS3) testing was conducted at the National Center for Asphalt Technology test track. Dry and wet-heated MMLS3 tests were done on five sections. The rutting performances of the sections under MMLS3 trafficking were compared with that under full-scale truck trafficking (truck test sections). A synthesis of the research included evaluation of results from laboratory tests done on cores taken from the MMLS3 test sections within and outside trafficked wheelpaths. Tests on the cores included wet and dry Hamburg wheel tracking, Superpave® shear tester frequency sweep, and semicircular bending (SCB) strength testing. Investigations included the evaluation of full-scale rutting data, laboratory wheel-tracking test results, and climatic data monitored on the track during full-scale truck trafficking. The project validated the rut prediction approach developed to compare MMLS3 and full-scale rutting performance and indicated that the MMLS3 may be used to estimate full-scale rutting at the track under specific conditions. Distress due to wet trafficking was also quantified as reduction in tensile strength as measured by the SCB. Conclusions were drawn and recommendations made for MMLS3 as well as continued full-scale testing at the track. Comparative full-scale rutting performance of the track sections evaluated may be quantified and ranked by the MMLS3 performance of these sections.
Superpave® Laboratory Compaction Versus Field Compaction
Authors: Peterson Robert L. , Mahboub Kamyar C. , Michael Anderson R. , Masad Eyad , Tashman Laith
Published: April 2007

Laboratory compaction is an important part of asphalt mix design. For the mix design process to be effective, laboratory compaction must adequately simulate field compaction. In this study mechanical properties measured with the Superpave® shear tester were used to evaluate field compaction and laboratory compaction. The field compaction consisted of three test sections with different compaction patterns. The laboratory compaction used the Superpave gyratory compactor with adjustments to several parameters. Results of this study indicate that current gyratory protocol produces specimens with significantly different mechanical properties than those of field cores produced with the same material and compacted to the same air voids. Results also show that adjustments to certain parameters of the gyratory can produce specimens that better simulate the mechanical properties of pavement cores.
Secret Lives of Containers: Evidence from Texas
Authors: Prozzi Jolanda , Spurgeon Kellie , Harrison Robert
Published: April 2007

In 2000, the Texas Department of Transportation contracted with the Center for Transportation Research (CTR) at the University of Texas, Austin, to analyze containerized freight movements in Texas. Although aggregate data are available on the container sector and global movements, including data on container manufacturing, steamship companies, container routes, vessel capacities, and costs and supply chains, little information is available on container movements in the United States. To shippers and those directly involved in the container sector, some data on container movements in the United States—including route choice—are available. However, for those involved in freight planning at the state level, such information remains somewhat of a mystery. To fill this void, the CTR research team sought the assistance of various transportation stakeholders involved in containerized freight movements in an effort to characterize and gain a better understanding of this important and growing component of the freight sector. A total of 31 telephone interviews were conducted, involving 3 major ocean carriers, 12 trucking companies, 8 freight forwarders, 7 container leasing companies, and 1 railroad representative. Questions addressed container ownership, liability at different stages of a movement, benefits of different types of leases, container tracking (state of practice), transfer costs, security risks, and the outcome of a container at the end of its useful life. This study provides planners and those outside the industry with information on this dynamic sector and likely future changes.
Trucking Efficiency Versus Transportation Efficiency: An Economic Evaluation of TRB Special Report 267
Authors: McCullough Gerard J.
Published: April 2007

TRB Special Report 267: Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles is critically evaluated. It is an important, congressionally mandated report that contains a series of conclusions and recommendations regarding truck size and weight (TS&W) regulations in the United States. The report concludes that increases in TS&W limits have great potential for increasing freight market efficiency but that safety and other effects are not well understood. To facilitate the liberalization of TS&W limits, the report recommends a revised regulatory regime that would involve federal supervision of state-set limits, with evaluation provided by an independent Commercial Traffic Effects Institute. This evaluation argues that the report focuses too narrowly on trucking efficiency and overlooks transportation efficiency. This narrow analytical perspective significantly limits its usefulness in establishing national transportation policy. Also, there is no analytical basis for the report's most important conclusions and recommendations, either in the report or in earlier TS&W studies evaluated by the Committee for the Study of the Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles.
Emerging Supply Chain Management Trends and Their Impact on Spatial Organization of Logistical Networks
Authors: Zografos Konstantinos G. , Giannouli loanna M.
Published: April 2007

Although the development of supply chain management trends has been the subject of substantial research, little attention has been devoted to examining the impact of the emerging supply chain management (SCM) trends on the spatial organization of the supply and distribution system. Specifically, the literature lacks an integrated methodological framework for examining the impact of emerging SCM trends on decision making relative to the spatial organization of logistical networks. This analysis has three purposes—( a) develop a conceptual framework for analyzing how decisions are made on the spatial organization of logistical networks, ( b) test the proposed framework via case studies, and ( c) develop a preliminary set of guidelines on the essential elements in making strategic logistical network design decisions. An interesting finding in implementing the proposed methodological framework, which was further supported by the limited empirical research, is that decision-making requirements vary substantially among the industrial and service sectors. This variance reflects differences in objectives and the extent of integration and collaboration of business entities along the respective supply chains.
Combinatorial Auctions for Transportation Service Procurement: The Carrier Perspective
Authors: Song Jiongjiong , Regan Amelia
Published: April 2007

The procurement of transportation services is an important task for shippers because of the need to control costs while providing high service levels. When shippers need to transport goods and materials, they seek transportation services from outside companies and typically issue a request for quotes from a group of carriers. The shippers then assign contracts on the basis of negotiated service charges. This process is similar to a simple sealed-bid auction in which each bidder submits a sealed bid for a single item. In the past, when shippers needed to procure transportation services for a set of distinctive delivery routes (called lanes), they would obtain quotes for each lane individually and repeat the simple auction process for each lane. Alternatively, they might negotiate for bundles of lanes with a single carrier at a time. However, in the last several years, software has been developed to enable shippers to make all lanes available for bidding simultaneously and to enable carriers to simultaneously bid on combinations of individual lanes. This method of awarding contracts, conventionally called a combinatorial auction, has resulted in significant cost savings for shippers. This research examines the benefits of combinatorial auctions primarily from the carrier's perspective. On the basis of a simple simulation model, preliminary findings suggest that carrier benefits can also be significant.
Economic and Financial Feasibility of Truck Toll Lanes
Authors: Holguin-Veras José , Sackey David , Hussain Sajjad , Ochieng Victor
Published: April 2007

The economic and financial feasibility of heavy-truck toll lanes was analyzed. This research expanded the line of inquiry of previous researchers by analyzing toll lanes for exclusive use by heavy trucks (i.e., large size and capacity). Implementation of such a toll system was studied relative to productivity changes, toll-lane fees, users' travel time and vehicle operating cost savings, and impact on infrastructure costs. The economic benefits were estimated using the Highway Design and Maintenance Standards Model developed by the World Bank. The analyses, complemented with sensitivity analyses of key variables, indicate that heavy-truck lanes are economically and financially viable.
Planning Truck-Only Lanes: Emerging Lessons from the Southern California Experience
Authors: Fischer Michael J. , Ahanotu Dike N. , Waliszewski Janine M.
Published: April 2007

Recent efforts to develop truck-only facilities in the United States are discussed. The rationale for truck-only highways is described, and the history of efforts to separate trucks and automobiles on the nation's roadways is presented. The truck lane program of the Southern California Association of Governments is one of the most ambitious programs of its type in the United States. Preliminary analysis of truck lanes for SR-60 and I-710 is described. SR-60 is an east–west corridor linking downtown Los Angeles with the warehouse and manufacturing districts of the San Gabriel Valley and the Inland Empire. 1-710 is the major access route to the ports of Los Angeles and Long Beach. Both freeways each have one of the highest truck volumes in California, and truck mobility on these corridors is a significant problem. Truck lane projects on SR-60 and I-710 are in the feasibility analysis stage and much has been learned in these early studies. Various issues are addressed, including the trade-off between limiting access to improve operational costs and limit capital costs, need to generate demand, time-of-day distribution of truck traffic and its relationship to potentially benefit truck mobility, and need for improved analytical tools. Also described are issues related to facility design and configuration, demand analysis, and toll analysis.
Effect of Sample Preparation on Chemical Composition and Morphology of Alkali–Silica Reaction Products
Authors: Hanson Karl F. , Van Dam Thomas John , Peterson Karl R. , Sutter Larry L.
Published: April 2007

The chemical composition and morphology of alkali–silica reaction (ASR) products is of great importance in studying the reaction mechanism and assessing the effectiveness of mitigation techniques. Epoxy-impregnated, polished thin sections were prepared from an in-service concrete pavement to examine ASR products that originate from chert particles in the fine aggregate. Both hydrous and anhydrous thin-section preparation techniques were used to investigate the influence of sample preparation on the results. Two distinct morphologies of ASR products were observed in the voids adjacent to the chert particles: a bladed crystalline type and a glassy amorphous type. The chemical compositions of the reaction products were determined with a scanning electron microscope via quantitative X-ray energy dispersive spectrometry. Both the chemical composition and morphology were influenced by sample preparation, with hydrous preparation resulting in leaching and degradation. It is recommended that, when conducting studies to assess the ASR mechanism and the effectiveness of mitigation techniques, anhydrous sample preparation be used.