bluuebunny/crossref_metadata_2025 huggingface dataset:
Permeability Performance of High-Performance Concrete Subjected to Various Curing Regimes
Authors: Myers John J.
Published: April 2007

Concrete technology has continued to advance throughout the years to meet the demands of designers and innovative structural systems. Traditionally, the most common means to specify durable concrete has been via specifying a maximum water-to-cementitious material ratio or a minimum cement content. With the advent of high-performance concrete (HPC), which often has higher contents of cementitious materials and a variety of admixtures, questions about permeability performance and alternative methods to specify durable concrete have arisen. The study conducted herein comments on the applicability of prescriptive specifications for HPC and investigates the influence of curing regimes and concrete temperature development during hydration on the permeability performance of HPC prestressed and precast beams and cast-in-place decks. These components were constructed for use in two recently constructed HPC bridges in Texas. Results indicate the benefits of an ASTM Class C fly ash from a permeability standpoint and emphasize that variables such as material constituents, curing condition, and concrete temperature play a dramatic role in the permeability performance of HPC.
Performance Characteristics of Synergy Fiber-Reinforced Concretes :Strength and Toughness Properties
Authors: Sundar S. , Ramesh K. P. , Pitts Charles , Ramakrishnan V.
Published: April 2007

The results of an experimental investigation of the performance characteristics of concrete reinforced with a newly developed synthetic synergy fiber are presented. A number of three-dimensionally reinforced concrete specimens (beams and cylinders) using four fiber dosages (0.5, 1.0, 1.5, and 2.0 vol%) were cast and tested to evaluate the strength and toughness characteristics. The strength tests included compressive strength, flexural strength (modulus of rupture), first crack strength, and impact strength. The toughness properties evaluated were modulus of elasticity; the toughness indices I5, I10, I20, and I30 and residual strengths calculated according to ASTM C1018 test procedure; and the flexural toughness factor and the equivalent flexural strength calculated according to the Japanese Society of Civil Engineers standard specifications. A new test method (ASTM C1399-98) was also used to determine the average residual strength (ARS) of the concretes reinforced with the four synthetic synergy fiber dosages. The fiber-reinforced concretes were mixed, placed, consolidated, finished, and cured under identical conditions. There was a significant increase in the flexural strength and a slight increase in the first crack strength as the fiber content was increased from 0.5 to 2.0 vol%. The ASTM toughness indices and the Japanese toughness factors and equivalent flexural strengths also increased significantly as fiber content increased. There was a tremendous increase in impact strength for an increase in fiber content. Very high average residual strengths (ASTM C1399) were obtained, and ARS values increased as fiber content increased.
Concrete Maturity Progress: Survey of Departments of Transportation
Authors: Tepke David , Tikalsky Paul J.
Published: April 2007

Results are provided from a concrete maturity survey that was distributed to representatives of 50 departments of transportation (DOTs) in the summer of 2000. The purpose was to display the state of national advancements and practices relating to concrete applications for predicting in situ portland cement concrete strength. Information such as DOT project and research details, method of maturity determination, state applications, and general attitudes toward the concept was requested. Representatives from 44 states replied to the 12-question survey. Results revealed that about 73 percent of the states that responded either have conducted or are currently involved in at least minor research with the concept. Furthermore, approximately 30 percent of the represented states have protocol or specifications governing the use of this developing technology. Representatives throughout the United States have reported that maturity is being used to predict critical strengths for such actions as pavement opening to the public; pavement opening to construction traffic; structural acceptance; and formwork removal for bridges, pavements, and other highway structures.
Freeway Quality of Service: What Really Matters to Drivers and Passengers?
Authors: Hall Fred , Wakefield Sarah , Al-Kaisy Ahmed
Published: April 2007

Although the concept of level of service for freeways is usually defined in terms of users’ perceptions, very few studies have sought drivers’ or passengers’ views about what is important to them. Such information is particularly important for the evaluation of extended trips on freeways as opposed to trips on a single section or segment. Such information is valuable not only for improving the Highway Capacity Manual but also for establishing appropriate criteria for assessment of intelligent transportation system proposals. The results of focus group sessions are reported in which a group of commuters discussed their views about determinants of the freeway quality of service that they experienced. Total travel time is the most important determinant for them, but a number of other aspects of the trip also matter, including safety, traveler information, and maneuverability (density). The importance of travel time is a reminder that travel is a derived demand, not something that commuters do for the pleasure of the drive.
Capacity Estimations for Type B Weaving Areas Based on Gap Acceptance
Authors: Lertworawanich Ponlathep , Elefteriadou Lily
Published: April 2007

Although weaving areas are one of the major types of highway facilities that have long been investigated by many researchers, the estimation of capacity along weaving areas has not been well researched or validated. Most of the literature concentrates on methods for the estimation of the speeds of weaving and nonweaving vehicles and of level of service (LOS). The 2000 Highway Capacity Manual (HCM) weaving methodology includes methods for the estimation of capacities for weaving segments, which are based on the assumption that the density at capacity is the boundary of LOS E–LOS F, 27 passenger cars/km/lane. The objective was to develop a method for the estimation of the capacities of Type B weaving areas based on gap acceptance and linear optimization. In addition, traffic data were obtained from a site located on the Queen Elizabeth Way in Toronto, Ontario, Canada, and were analyzed to identify capacity. Field estimates of capacity were compared with those resulting from the new methodology and from the 2000 HCM methodology. It was concluded that the proposed methodology provides better estimates of the capacity of the study site than the 2000 HCM methodology does when the results obtained by both methodologies were compared with field observations. The collection of additional data is required to validate the proposed model for a variety of Type B weaving segments and for various traffic and highway design conditions.
Defining Freeway Capacity as Function of Breakdown Probability
Authors: Lorenz Matt R. , Elefteriadou Lily
Published: April 2007

The need for an enhanced freeway capacity definition that incorporates the probabilistic nature of the freeway breakdown process is addressed. This is investigated through an extensive analysis of speed and volume data collected at two freeway bottleneck sites in Toronto, Ontario, Canada. At each site, the freeway breakdown process was examined in detail for more than 40 congestion events occurring during the course of nearly 20 days. Preliminary models were developed for each site. These models are used to describe the probability of breakdown versus the observed flow rate and to examine the implications that this probabilistic approach to breakdown has on the current definition of freeway capacity. A revised, probabilistic freeway capacity definition is proposed for use in future editions of the Highway Capacity Manual.
Effect of Weather on Free-Flow Speed
Authors: Kyte Michael , Khatib Zaher , Shannon Patrick , Kitchener Fred
Published: April 2007

The effects of poor weather conditions on free-flow speed on a rural Interstate freeway are considered. It was found that free-flow speed is affected by pavement conditions, visibility, and wind speeds. It is also suggested that poor weather conditions occur with some degree of frequency in a number of U.S. cities and that the effects of poor weather should be considered in such cases as part of capacity and level-of-service analyses.
Simulation-Based Study of Traffic Operational Characteristics at All-Way-Stop-Controlled Intersections
Authors: Tian Zong Z. , Kyte Michael , Vandehey Mark , Kittelson Wayne , Robinson Bruce
Published: April 2007

Traffic operational characteristics at all-way-stop-controlled intersections were investigated by using AWSIM, a microscopic simulation model. The effects of vehicle arrival distribution and traffic volume split on intersection operations were studied. Traffic operations were analyzed from delay, capacity, and queue length perspectives. Empirical models were developed on the basis of simulation results for delay and queue length estimations. It was found that longer delays and queues resulted from platoon arrivals. Higher intersection capacity or lower control delay can be achieved with even volume splits on all the approaches. A generalized form of the delay model showed a better correlation compared with those for exponential-form models used by other studies. A nonlinear relationship was found to exist between the 95th percentile queue length and the average queue length. An empirical model was developed on the basis of the simulation results for estimation of the 95th percentile queue lengths. The model proves to be reliable and easy to use on the basis of field studies, and it fulfills one of the major shortcomings in queue estimation, which is currently unavailable in the Highway Capacity Manual.
Capacity at Unsignalized Intersections Derived by Conflict Technique
Authors: Brilon Werner , Wu Ning
Published: April 2007

A new simplified theoretical approach for the determination of capacities at unsignalized intersections has been developed on the basis of the method of additive conflict streams. This method is much easier to handle than the method of gap acceptance. It avoids many of the theoretical complications inherent in the method of gap acceptance, which, under certain circumstances, seems to be unrealistic. The new method has been developed for potential intersection configurations when one street has priority over the other. A calibration of the model parameters is given for German conditions. The new procedure can deal with shared lanes, short lanes, flared entries, and cases of so-called limited priority. For the estimation of traffic performance measures such as average delay and queue lengths, the classical methods can be applied.
Derivation of Capacity Equation for Roundabout Entry with Mixed Circulating and Exiting Flows
Authors: Hagring Ola
Published: April 2007

A gap acceptance model for roundabouts that takes the proportion of exiting vehicles into account was developed. Exiting vehicles are assumed to influence the gap acceptance process in the following way: when they leave the roundabout, new gaps that consist of combinations of old gaps arise. The distribution of the new gaps is obtained by a convolution of the distribution of the old gaps. It is shown that the proportion of exiting vehicles can have a strong effect on the entry capacity of a minor stream. The effect depends on where the exiting point is situated, which in turn depends on the ability of the minor-stream driver to detect an exiting vehicle. The model attaches greater importance to the proportion of exiting vehicles than the macro models do. This can partly be explained by an erroneous placement of the exiting point. The model has various implications for the measurement of critical gaps. If the proportion of exiting vehicles is large, critical gaps will be overestimated because of the failure to take into account the minor-stream vehicles that are waiting for exiting vehicles.
Estimation of de Facto Left-Turn Lanes at Signalized Intersections
Authors: Janson Bruce N. , Finochio Michael R. , Karimkhani Elahe
Published: April 2007

Depending on vehicle delays or turning restrictions at a multilane approach to a signalized intersection, vehicles permitted to make left turns either share the leftmost lane with through vehicles or use the leftmost lane exclusively. An exclusive left-turn lane is explicitly identified by a turning restriction, whereas a de facto left-turn lane occurs when excessive delays and queues discourage through vehicle drivers from using the left-turn lane. However, Highway Capacity Manual (HCM) procedures for the identification of a de facto left-turn lane require left-turn volumes and opposing volumes to be excessively high for a de facto left-turn lane to occur because HCM overestimates the effective green time of a shared left-turn lane. As a result, HCM may not indicate a de facto left-turn lane, even though its delay is much higher than the delay of adjacent lanes. The HCM estimation of percent left turns in the left-turn lane is modified such that a de facto left-turn lane is indicated when its average delay is reasonably greater than the average delay for the adjacent lanes. Examples show the effects of these modifications in comparison with the effects of the HCM procedure. These suggested improvements need to be refined with further research and validation, as recommended.
Analysis of Arrival Type Estimation Procedures
Authors: Eidson William C. , Bullock Darcy M.
Published: April 2007

The estimation of arrival type, an important part of the 1997 Highway Capacity Manual (HCM) procedure for estimation of delay and level of service (LOS) at signalized intersections, is considered. The research examines whether arrival type can be reliably estimated by the procedures outlined in HCM. The objective is to review the impact that arrival type has on delay estimation and to evaluate quantitatively the variance and error of arrival types estimated under controlled conditions. Progression quality issues are discussed, and potential additions and clarifications are explored. To understand the impact that arrival type estimations have on delay results, an experiment was conducted using the HCM delay estimation procedure. Participants were shown video clips of traffic at seven different intersection approaches and were asked to indicate the observed arrival type. The results are categorized by response groups (traffic engineering professionals, high school students, and university students) and approaches and are compared, with results calculated by HCM procedure. The results show trends of inconsistent responses when the responses are compared within groups, between groups, and with the calculated arrival types. On the basis of the response trends, several additions to the HCM method are explored. Recommendations are to include the impact of green split percentages, estimation of arrival types for each lane group, and general clarification of instructions for estimation of arrival types. The study results suggest that these changes and clarifications should be considered for incorporation into the HCM delay estimation and LOS procedure for signalized intersections.
Estimating Vehicle Stops at Undersaturated and Oversaturated Fixed-Time Signalized Intersections
Authors: Rakha Hesham , Kang Youn-Soo , Dion François
Published: April 2007

State-of-the-practice models for estimation of the number of vehicle stops at signalized intersections are first reviewed, and then two approaches are introduced for the computation of the number of vehicle stops at undersaturated and oversaturated signalized intersections. The first approach uses a microscopic model that computes instantaneous partial and full stops for undersaturated and oversaturated conditions by using second-by-second speed measurements. This model, in particular, has been introduced in the INTEGRATION traffic simulation software. The second model is an analytical formulation derived from the proposed microscopic model that computes the number of vehicle stops for oversaturated approaches over a given analysis period. Finally, comparisons of the stop estimates produced by the two proposed models with estimates obtained from current state-of-the-practice analytical models demonstrate the validities of both models in their respective domains of application.
Investigation of Density and Flow Relationships in Congested Traffic with Videogrammetric Data
Authors: Ioerger Thomas R. , Meeks John H. , Nelson Paul
Published: April 2007

Traffic congestion is a major problem on U.S. highways. Studies and modeling of congestion can have important implications for efficiency, safety, and planning of transportation systems. A variety of theoretical models have been proposed to explain the behavior of congested traffic, including the recent interesting postulation of “synchronized flow” states and the treatment of these as phases (in the statistical mechanics sense). However, empirical methods for the identification and characterization of such patterns of congestion have been hampered by a lack of objective and quantitative characterizations of these patterns. An empirical study of the patterns of traffic in a data set from a congested, five-lane basic section of freeway is presented. These data were collected by videogrammetry, which provides additional information (on the spatial variation) in comparison with the information provided by other sensor technologies. With these data, a macroanalysis of the relationships among flow, density, and velocity was performed, and a linear (decreasing) relationship between velocity and density was found, with the attendant quadratic dependence of flow on density. Through a microanalysis, it was observed that depressions in velocity under congested conditions appear to be correlated with “constrictions” (waves of reduced speed between two waves of higher speed) that propagate backward, and a signal detection algorithm, based on convolutions of the density gradient, was designed for recognition of these events in a time series.
Stochastic Modeling and Design of Vehicular and Pedestrian Networks
Authors: Smith J. MacGregor
Published: April 2007

One of the most important problems in today’s engineering, planning, and design community is the performance modeling and design of vehicular and pedestrian traffic networks. Although there are many deterministic models for these problems, few stochastic models other than simulation have been developed. State-dependent queues and finite queuing network models are crucial tools for the topological network design of traffic networks, routing of occupants, and the capacitated allocation and design of resources to accommodate occupant traffic. The latter network design and analysis problems are the focus of the present effort.
Destination Choice Modeling for Home-Based Recreational Trips: Analysis and Implications for Land Use, Transportation, and Air Quality Planning
Authors: Pozsgay Michael A. , Bhat Chandra R.
Published: April 2007

Attraction-end choice studies have primarily focused on nonurban recreational trips or nonrecreational urban trips. Relatively little attention has been focused in the literature on urban recreational trips. However, urban recreational trips are contributing increasingly to overall urban travel. Attraction-end choice models for home-based urban recreational trips are examined. A nonlinear-in-parameters multinomial logit model is estimated using the 1996 Dallas–Fort Worth household activity survey. The effects of level-of-service, zonal attribute, trip attribute, and socio-demographic variables on recreational attraction-end choice are examined, and the implications of the results for land use, transportation planning, and air quality analysis are discussed.
Computational Issues in Increasing Spatial Precision of Traffic Assignments
Authors: Horowitz Alan J.
Published: April 2007

The practical feasibility is demonstrated of a traffic assignment method, dubbed area-spread assignment, that incorporates information on the spatial relationships between nodes, links, and zone boundaries. Tests of area-spread assignment were performed on networks from Fredericton, New Brunswick, and Racine, Wisconsin. To eliminate the effect of errors from other model steps in the tests, comparisons were made with a detailed network in Fredericton that contained all streets in the city and extremely small zones. The tests indicated that there is a substantial difference between area-spread assignment and a traditional assignment using centroid connectors. Area-spread assignment did a better job of replicating volumes on the detailed network, although computation times were much longer.
Breakeven Analysis for Statewide Intelligent Transportation System Project Identification and Assessment
Authors: Peng Zhong-Ren , Beimborn Edward
Published: April 2007

The use of breakeven analysis as a tool to assess the benefits of intelligent transportation systems (ITS) at the system level in systemwide sketch planning is discussed. The breakeven analysis was developed on the basis of the SCRITS (SCReening for ITS) spreadsheet template and used data from Madison, Wisconsin, as a case study and provided considerable in sight into the magnitude of the potential benefits of different ITS programs. The analysis can help identify critical performance variables in the assessment of ITS benefits. Breakeven analysis coupled with sensitivity analysis can be used to identify and assess ITS projects for deployment in the ITS planning and programming process with limited data. It can be used to screen, prioritize, and select ITS projects among different ITS options. It can also be used to compare ITS projects in different geographic locations on the basis of different traffic data and breakeven points. The method is also useful in the identification of data needed for detailed ITS project assessments and evaluations. Such data should include before-and-after studies of ITS deployments as well as refined cost data and traffic flow estimates. The case study identified the breakeven points of several ITS deployment options, including ramp metering, traveler information systems, emergency response systems, and commercial vehicle operations under a variety of scenarios. These results can be used to identify and operate ITS projects so that they are likely to have the greatest payoff from their deployment.
Planning Large Transportation Projects: Six-Stage Model
Authors: Ardila Arturo , Salvucci Fred
Published: April 2007

A model is presented that describes the life of large transportation projects. The model has six stages, each one devoted to a different part in the life of the project: prehistory of the project, project development, procurement, implementation, operations and maintenance, and long-range impacts and economic restructuring. This six-stage model should help planners and project promoters go through the task of developing and implementing large transportation projects. The model describes the different issues in each stage and embedded in the discussion are ways for addressing them. The political, institutional, as well as technical aspects are addressed, and they are linked to show how they affect the evolution of the project. The analysis presented in the six-stage model can be inter preted as a call for planners and project promoters to acknowledge that large transportation projects are very complex and that planning and implementing them requires planners and promoters to behave in a strategic way that includes intertwining technical and political issues.
Prioritizing Proposed Transportation Improvements: Methods, Evaluation, and Research Needs
Authors: Turochy Rod E.
Published: April 2007

Since the costs of proposed transportation projects typically exceed available funding, the process by which projects are selected and prioritized for development is scrutinized by a wide variety of stakeholders. The U.S. Congress and state legislatures are increasingly involved in selecting projects, and thus some projects do not evolve from the transportation planning process. Oversight panels, special interest groups, and the public are applying pressure to clarify the process by which proposed projects are prioritized and to minimize the impact of politics. A rational tool that lays out a clear procedure can assist decision makers in selecting and prioritizing potential improvements, make the process more transparent, and strengthen the link between planning and programming. Several such tools have been proposed, and many state and local transportation agencies are using some of them. These instruments vary widely in objectivity, the factors considered in evaluating potential transportation improvements, and output formats. The role they play in programming decisions also varies, but their use makes available more information to interested parties, including those vested with the authority to make decisions about transportation programming.
Planning for Megacontainerships: Statewide Transportation Planning Approach
Authors: Bomba Michael S. , Harrison Robert , Walton C. Michael
Published: April 2007

The emergence of the megacontainership, exceeding 5,000 twenty-foot equivalents (TEUs) in capacity, is of interest to shippers, logistics companies, port authorities, and those engaged in maritime planning. Where such ships unload, rather than transship, state transportation agencies responsible for multimodal planning and highway connectivity are affected by greater flows of containers passing through the load center. A planning process is described that can be applied at the state level to select a megacontainership site. It was developed as part of a Texas Department of Transportation research study into the effects of containerships on the state transportation system but is generic in structure and can be applied at port sites located in other parts of the United States.
Measurement of Passenger Vehicle Wait Times at San Ysidro, California, Port of Entry
Authors: Banks James H.
Published: April 2007

As border communities grow and increase in economic integration, measurement of queuing delays for passenger vehicles at border crossings becomes more important. At the San Ysidro, California, Port of Entry, recent research has included development and testing of techniques for measuring queuing delays. These measurements were intended to be used as traveler information and for monitoring compliance with traffic management objectives. Techniques tested at San Ysidro involved indirect measurement of queue sizes and wait times. These measurements displayed problems with both accuracy and precision. Problems with accuracy appear to be related to data quality and probably can be overcome by better data collection methods. Problems with precision are an inherent feature of indirect measurement techniques and are the result of the variability of queue density and vehicle-processing rates about their mean values. Monitoring efforts are intended to track changes in delay over long periods of time and are relatively insensitive to the precision of the measurements. Traveler information services, however, depend on the ability to closely approximate the delays experienced by individual travelers and are thus highly sensitive to precision. Consequently, the emphasis on measuring queuing delays at border crossings should normally be on monitoring rather than on traveler information.
Validation of HIPERPAV for Prediction of Early-Age Jointed Concrete Pavement Behavior
Authors: Mauricio Ruiz J. , Kim Patricia J. , Schindler Anton K. , Otto Rasmussen Robert
Published: April 2007

HIPERPAV is a computer program that was developed to predict the time growth of early-age portland cement concrete strength and stresses in jointed concrete pavements for the prediction of cracking. Each individual environmental, construction, design, and mix design input that influences early-age pavement behavior can be adjusted to find the optimum paving solution. A design that minimizes stresses and maximizes concrete strength will increase the potential for an extended service life. FHWA, aware of the benefits that HIPERPAV can provide in the field, provided funding for experimental validation. The results of this validation are presented. The experimental field instrumentation efforts are described and the analyses performed are discussed. The end result of validating HIPERPAV is increased confidence in the accurate prediction of early-age pavement behavior.
Characterization of Stiffness Parameters in Design of Continuously Reinforced and Jointed Pavements
Authors: Jeong Jin-Hoon , Zollinger Dan G.
Published: April 2007

Key performance factors related to the deterioration of a joint or crack stiffness in terms of the prediction of faulting or punchout distress are characterized. Over the past decade, several advancements have been made that address various stiffness components that contribute to the transfer of load between adjacent slab segments. An approach is presented that addresses key stiffness components in a rational format in terms of a mechanistic process to address faulting and punchout development. This approach is suitable for both the design and rehabilitation of concrete pavement systems. Components of load transfer are discussed and detailed along with key material parameters relative to a loss of stiffness mechanism triggered by repetitive loading. This discussion leads to a mechanistic erosion model to provide a tie between joint deterioration of the development of voids created by erosive action. This work provides a basis of follow-on efforts to illustrate the sensitivity of key design parameters in an overall design and rehabilitation process.
Design, Construction, and Maintenance Guidelines for Porous Asphalt Pavements
Authors: Moore Lucinda M. , Hicks R. G. , Rogge David F.
Published: April 2007

Oregon has been using open-graded hot mix on its roadway system since the late 1970s. Because of the performance of these early jobs (and the continued good performance of these mixes), open-graded hot mix has been the preferred choice for a surface course on Oregon highways. The following are described with respect to the use of these mixes in Oregon: historical perspective; design, including mix and structural design; construction, including quality control/quality assurance considerations; and maintenance and rehabilitation practices with porous pavements. The continued success of the use of these materials from both a performance and a public acceptance standpoint indicates they will be the pavement of choice in Oregon for the foreseeable future.
Using Pavement as Solar Collector: Effect on Pavement Temperature and Structural Response
Authors: van Bijsterveld W. T. , Houben L. J. M. , Scarpas A. , Molenaar A. A. A.
Published: April 2007

Using asphalt pavements as a solar collector is a subject of current interest in the Netherlands. Some thermal analysis research has already been done. The effects of a system for cooling and heating asphalt pavements on the durability of the pavement structure are examined. With the finite element program FEMMASSE, thermal analyses have been done based on measuring data from a field test in the northern Netherlands, where polyethylene tubes were built in a main road to control the temperature of the pavement. Subsequently, a model for structural analysis was built by means of the finite element system CAPA 3D (computer-aided pavement analysis). The model was based on temperature distribution according to the thermal analysis. From these analyses it appears that high peak values in the stresses and strains arise around the tubes, which might affect the lifetime of the system negatively. Considering the research findings of the investigation it is concluded that the issue of energy extraction from asphalt pavements involves several complex engineering and financial issues that must be resolved before effective utilization is possible.
Thin Bonded Concrete Overlays in Illinois: Preliminary Report on Performance
Authors: Volle Tessa H.
Published: April 2007

In recent years, two bonded concrete overlays (BCO) were constructed in Illinois. The first was constructed in 1994-1995 on a section of Interstate 80 (I-80) east of Moline. The second BCO was placed in 1996 on a section of Interstate 88 (I-88) further east of Moline. Both the I-80 and the I-88 BCO sections were placed on 203-mm (8-in.) thick continuously reinforced concrete pavements. The I-80 BCO was designed as a 102-mm (4-in.) thick plain concrete overlay. It includes six experimental sections with various percentages of microsilica added to the standard mix design and different bonding agents between the original pavement and the BCO. The I-88 BCO was designed as a 76-mm (3-in.) thick plain concrete overlay. It includes two experimental sections involving different surface preparation methods before BCO placement. Performance of the BCO to date is summarized. Visual distress surveys were conducted annually on selected test sections of the I-80 and I-88 overlays. The I-80 and I-88 overlays were also tested annually for international roughness index values. Condition rating surveys were conducted every 2 years on I-80 and I-88 to define the overall condition of the pavement. The results of the tests and surveys are included. Significant differences have been observed in the performance of the I-80 and I-88 BCO. Although the I-88 BCO has been performing very well, the I-80 BCO, particularly the overlay in the eastbound direction, needed rehabilitation only a few years after construction.
Early Age Stresses and Debonding in Bonded Concrete Overlays
Authors: Lange David A. , Shin Hak-Chul
Published: April 2007

Bonded concrete overlays are a cost-effective strategy for rehabilitating and strengthening old concrete pavements. Volume changes of the over lay concrete may cause debonding at the interface between old and new concrete or surface cracking, detrimentally affecting long-term performance of the pavement. Experimental measurements and numerical analyses were pursued to understand distribution of stress arising from thermal change or drying shrinkage under restrained conditions. Laboratory overlay specimens were made to measure opening displacement at the interface. Debonding profiles at the interface were determined by using a dye technique. A finite element model was developed to study debonding behavior and crack tendency due to volume changes. Physical experiments were used to define nonlinear gradients of drying shrinkage and bond strengths for input into the model. The model was validated by comparing the predicted opening displacements and debonding profile with the experimental measurements. The results indicate how high-performance concrete mixtures may be problematic for overlay applications if full wet curing is not used.
Measuring Divided-Attention Capability of Young and Older Drivers
Authors: Mourant Ronald R. , Tsai Feng-Ji , Al-Shihabi Talal , Jaeger Beverly K.
Published: April 2007

A divided-attention task was used to measure the ability of young and older drivers to obtain information from an in-vehicle display. Performance with the in-vehicle display was compared with performance with information superimposed on the driving scene. Ten young and 10 older drivers drove on a curvy road by using a fixed-based driving simulator. Older drivers were less accurate in obtaining information from the in-vehicle display, the average lane-position error of older drivers was greater, and older drivers spent more time driving outside their lanes. These results suggest that the use of in-vehicle displays, in their present configuration, is not appropriate for older drivers. When viewing information superimposed on the driving scene, older drivers were much more accurate and controlled their vehicles better. This indicates that the poor performance of older drivers with the in-vehicle display was due to vision-related changes, such as longer eye accommodation times, rather than cognitive processes.
Driver Knowledge and Beliefs About Antilock Brake Systems: Have Preconditions for Behavioral Adaptation Been Met?
Authors: Lee-Gosselin Martin , Fournier Pierre-Sébastien , Béchard Isabelle
Published: April 2007

Some studies suggest that the benefits of antilock brake systems (ABS) may be offset through behavioral adaptation, such as driving faster or following closer. Whether preconditions for behavioral adaptation exist was examined by investigating driver knowledge and beliefs about ABS. Telephone interviews were conducted throughout Quebec early in 1999 with principal drivers of a stratified random sample of 404 drivers with currently registered light-duty vehicles, registered to the same person for at least 18 months. The response rate was 82 percent of 492 reached. Only medium-range and high-end 1990-1995 vehicles, for which ABS was either standard equipment or unavailable, were selected. The protocol involved mostly open questions that encouraged respondents to reveal their knowledge and beliefs with minimal prompting. The results indicated an important lack of understanding, on the part of a majority of drivers, regarding the functioning and use of ABS. This varied from an inability to identify conditions in which ABS is favorable or unfavorable to serious misconceptions; about 25 percent were wrong about whether their vehicle was ABS equipped. Cognitive preconditions for behavioral adaptations—sometimes increased prudence—were found for a minority of this sample, and there may be a relationship between a low level of knowledge and the perceived possibility of driving faster with these brakes. There appears to be a case for improved public and dealer-delivered information on the advantages and disadvantages of ABS in different driving conditions, which if balanced should not increase unsafe behavioral adaptation.
Field Study of Driver’s Curve-Detection Performance in Daytime and Nighttime
Authors: Hagiwara Toru , Suzuki Kento , Tokunaga Roberto A. , Yorozu Naoki , Asano Motoki
Published: April 2007

Effects of road scenes and traffic-control devices on driver’s curve-detection performance were investigated. Field experiments were conducted on a 19-km section of highway running through a hilly area in Hokkaido, Japan. The driver obtained directional information from the road scene ahead and traffic-control devices at the beginning of the target curve. Road scene characteristics were determined subjectively. Configurations of traffic-control devices at 32 curves were obtained from the road maintenance database and were measured on site for each curve. Each of the 17 participating subjects drove an instrument-equipped vehicle and pressed a button as soon as he or she recognized the direction of the target curve. Detection distance of each curve was measured. The experimenter determined the maximum detection distance (MDD) of each target curve. A curve-detection index, defined as the detection distance divided by the MDD, was used to compare detection performance for each curve. Characteristics of detection performance for the curves were determined by a cluster analysis and regression analysis. Curves were classified into five groups according to the results of the cluster analysis. Results of the within-subject regression analysis revealed that subjects driving in the daytime obtained directional information about the curve from the road scene, whereas in the nighttime the lighting midway through the curve had a greater effect on detection performance. Results indicate that visual cues should be considered when traffic-control devices are installed at a curve, and appropriate traffic-control devices should be selected to increase the detection performance of a curve.
Driving Cessation Among Older People: When Does It Happen and What Impact Does It Have?
Authors: Rosenbloom Sandi
Published: April 2007

The mobility effects of driving reduction and cessation are evaluated by examining the before and after travel behavior of 42 older drivers in Tucson, Arizona, who reported that they had ceased to drive 1 year after an initial interview. Driving cessation was greater among women, those with lower incomes, and people of color. A substantial number said that they were not sure if their cessation was permanent. More than three-quarters of those who stopped driving relied on car rides to meet their travel needs. The analyses indicate a large drop in common measures of mobility for those who ceased to drive over 1 year’s time and that those who stopped driving had initially traveled substantially less than those who continued to drive 1 year later. The study confirms that there are sometimes drastic declines in mobility with driving cessation, but it also indicates that the impact of driving reduction on the mobility of people who are still drivers is underestimated.
Investigation of Winter-Weather Speed Variability in Sport Utility Vehicles, Pickup Trucks, and Passenger Cars
Authors: Padget Eric D. , Knapp Keith K. , Thomas Gary B.
Published: April 2007

The different characteristics of sport utility vehicles (SUVs), pickup trucks, and passenger cars put the smaller vehicle at a disadvantage in a crash. A larger difference in the speed of two vehicles can also increase crash severity, and increases in speed variability on a roadway can decrease overall safety. Research investigated whether drivers of SUVs, pickup trucks, and passenger cars choose different vehicle speeds during winter weather. Vehicle speed, roadway condition, time of day, and vehicle type were recorded during normal and winter-weather conditions. The results indicated that winter-weather vehicle speeds for all three vehicle types were significantly less than normal and that during the day a large percentage of the speed reduction occurs after snow begins to accumulate in the gutter pans of the roadway. Vehicle speed variability also increases during winter-weather conditions. The average SUV speed was statistically higher than the average passenger car speed during the day for four of the five winter-weather roadway surface conditions observed. The magnitude of the speed differences increased with roadway snowcover, but it was always less than 5.6 km/h (3.5 mph). The winter-weather speed differences between passenger cars and SUVs, although small, may have safety implications. The safety of winter-weather roadways may be lower than before the increase in SUV use, more-severe winter-weather crashes may occur between passenger cars and SUVs, more SUV run-off-the-road crashes might occur, and the safety benefits of larger vehicle characteristics may be smaller than believed.
Motor Carrier Safety: Crash Patterns of Inspected Commercial Vehicles
Authors: Thakuriah Piyushimita , Yanos George , Lee Jung-Taek , Sreenivasan Athreya
Published: April 2007

A linked database comprising state and federal roadside inspection, crash, and firm records of commercial motor vehicles is described. This combined database links information on vehicles inspected in the state of Illinois to the crashes that these vehicles may have been involved in anywhere within the United States. Two issues are addressed: determination of the components of an inspection-violation detection rate and the relationship between inspections and crashes. The first issue involves an attempt to quantify the components of a violation detection rate. For the second issue, four separate research questions are posed. The results of the second component indicate that there is no evidence that a significant difference exists in the expected number of crashes in which vehicles incurring zero violations were involved compared with the expected number in which vehicles incurring one or more violations were involved. About 2 percent of all inspected vehicles, which incurred zero violations, were subsequently involved in crashes. With every increase in the number of violations, the percent of vehicles involved in crashes increases by about 0.04. Further, a smaller percentage of vehicles that incur zero violations in Level I inspections are subsequently involved in crashes, compared with vehicles incurring zero violations under all Level II and Level V inspections. Moreover, the rate of increase in the percent involvement in crashes is greatest for vehicles incurring a positive number of violations in Level I inspections compared with vehicles subject to other types of inspection.
Development of Intrastate Inspection Selection System for Wisconsin
Authors: Smith Robert L. , Januario Marcus H. , Juni Emil
Published: April 2007

Roadside safety inspections have been an important component of federally supported programs to improve motor carrier safety. The inspection selection system (ISS) and its successor, ISS-2, were designed to help roadside inspectors target the vehicles of Interstate carriers with the worst past safety performance. ISS was used as a starting point for developing an intrastate ISS for Wisconsin. Logistics regression was used to identify the relevant independent variables. The logit model estimates the probability that a vehicle will be found to have an out-of-service (OOS) safety violation. An alternative to the logit model, a simple direct-estimation technique that uses the total OOS rate for a motor carrier, was found to produce the highest success rates in predicting inspections that result in an OOS violation. The model can be implemented as a field inspection tool and as a means to generate a list of intrastate carriers ranked by their historical OOS violation record.
Crashes Involving Long Combination Vehicles: Data Quality Problems and Recommendations for Improvement
Authors: Scopatz Robert A.
Published: April 2007

In 1999–2000, the Automobile Association of America Foundation for Traffic Safety conducted a research program to identify the barriers to analysis of large-truck safety experience in the United States. The primary focus was on so-called longer combination vehicles (LCVs)—the doubles and triples running on major highways throughout the country. Five states (Florida, Idaho, Nevada, Oregon, and Utah) participated in a review and evaluation of their data-collection and analysis practices. Two of the states (Oregon and Utah) also participated in an audit of completed crash reports for crashes involving large trucks and specifically doubles and triples. The results show that none of the five states has a crash-reporting system that adequately supports the analysis of LCV safety. In general, there is a lack of reliable data on the exact configuration of vehicles involved in crashes and a lack of specific measures of exposure for LCVs. Without good data on configuration and good measures of exposure, the main question about LCV safety (i.e., are they more or less safe than other large commercial motor vehicles?) cannot be answered empirically. The report concludes with a series of recommendations for improving the quality of data for crashes involving large trucks and a state’s ability to analyze LCV crashes specifically.