bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Global Positioning System Data for Field Evaluation of Energy and Emission Impact of Traffic Flow Improvement Projects: Issues and Proposed Solutions
Authors: Rakha Hesham , Dion Francois , Sin Heung-Gweon
Published: April 2007

Traffic-operational projects typically are evaluated by using several measures of effectiveness, including vehicle delay, queue sizes, and vehicle stops. Other emerging measures include vehicle fuel consumption and emissions. Although these emerging measures are difficult to determine in the field, they can be estimated by using second-by-second speed measurements of individual vehicles with Global Positioning System (GPS) technologies. GPS can provide such information with relatively high accuracy (within 1 m/s), but the presence of any erroneous data in the measured data as a result of signal losses may result in unrealistic vehicle fuel consumption and emission estimates. The ability of various data-smoothing techniques to remove such erroneous data without significantly altering the underlying vehicle speed profile is investigated. The techniques reviewed involve differentiating the measured speed profile to generate an acceleration profile that is checked for validity. Several smoothing techniques are then applied to the acceleration profile, including data trimming, simple exponential smoothing, Epanechnikov kernel smoothing, robust kernel smoothing, and robust simple exponential smoothing. The results of the analysis indicate that the application of robust smoothing (kernel of exponential) to vehicle acceleration levels, combined with a technique to minimize the difference between the integral of the raw and smoothed acceleration profiles, removes invalid GPS data without significantly altering the underlying measured speed profile. A sensitivity analysis also demonstrates that the proposed datasmoothing technique can efficiently smooth random variations in speed profiles due to errors in GPS speed measurements.
Analytic Minimum Impedance Surface: Geographic Information System-Based Corridor Planning Methodology
Authors: Grossardt Ted , Bailey Keiron , Brumm Joel
Published: April 2007

Highway corridor alignment presents a highly complex decision environment in which a variety of social, environmental, and economic factors must be defined and weighted and trade-offs must be evaluated. These data vary widely in format and quality. Stakeholders from various groups, often with competing interests, should be integrated into this process efficiently to determine objectives, to select data, and then to quantify the importance. Corridor planning is therefore an appropriate domain for the development and application of enhanced methodologies that conjoin multicriteria decision-support techniques with the spatial analytic and presentation capacities of a geographic information system. The analytic minimum impedance surface (AMIS) methodology is presented, and its application to a case study in the southeastern United States is evaluated. AMIS features the structured integration of stakeholder input into a hybrid analytic hierarchy process. The advantages of the approach are highlighted, along with the significance of process design in building an effective methodology. Several potential applications are discussed. Conceptual constraints and problems related to the implementation of AMIS are set forth, and future enhancements are posited.
Using Global Positioning System to Improve School Bus Routing and Scheduling
Authors: Rhoulac Tori D. , Rouphail Nagui , Tsai Jeffrey C.
Published: April 2007

School bus routing and scheduling in North Carolina are completed by using the transportation information management system (TIMS), according to state legislative mandate. TIMS uses an optimization algorithm to generate acceptable route alternatives to best serve the transported students and to minimize the required number of buses. This algorithm uses link travel times and speeds encoded in the geocode (digitized map) to determine the routes for each school bus in the state. The speeds and travel times used by TIMS have no mathematical basis and have not been calibrated for conditions in North Carolina. The encoded speeds are simply reductions of the posted speed limit to account for student stops and the bus’s general inability to reach the posted speed. There is a need for models that can accurately estimate link travel times and student loading times so that TIMS can provide better estimates of optimal routes. On-board mobile Global Positioning System equipment was used on several school bus routes throughout the state to collect the data necessary for model development and validation. Two student loading time models were developed: a general model that can be used in an urban, a suburban, or a rural area, and an urban-specific model, which involves fewer predictor variables. Link travel-time models were developed according to the two most pertinent factors: link length and traffic control device type at the link’s end. Model validation was successful, and now more-efficient school bus routes can be developed because of more-accurate geocode speed and travel-time estimates.
Using a Geographic Information System for Automated Decision Making in Highway Cost Analysis
Authors: Jha Manoj K.
Published: April 2007

Highway planning involves selection of a cost-effective corridor in an environmentally responsible manner. With the recent advances in geographic information systems (GISs), most environmental, real estate, and design databases and maps are available in the form of GIS layers. Several mathematical optimization algorithms have been developed to optimize highway alignments, among which genetic algorithms appear most promising because of their ability to avoid getting trapped in local optima. In recent studies, a GIS was integrated with genetic algorithms, enabling full exploitation of GIS features in highway alignment optimization. Those optimization models still lack some dynamic decision-making capabilities during optimal search, such as consideration of bridge cost when rivers are encountered and intersection and interchange costs when roads are encountered. A study that used a GIS as a dynamic decision-making tool in performing highway optimization is presented. Algorithms are developed to estimate costs associated with bridges, tunnels, intersections, and overpasses. A fully automated model is developed that allows dynamic data exchange between the GIS and the optimization algorithm. An example that uses real geographic information from Maryland is presented. The results indicate that consideration of bridges and intersections is significant in highway alignment optimization.
Public Perceptions of the Midwest’s Pavements: Explaining the Relationship Between Pavement Quality and Driver Satisfaction
Authors: Giese James K. , Griffin Robert J. , Kuemmel David A.
Published: April 2007

A three-phase study involving focus groups and sample surveys was conducted in three Midwestern states to assess the amount of satisfaction that motorists who drive on rural, two-lane state highways have with the pavement characteristics of those highways and to explain the relationship between the actual physical condition of the pavements and motorists’ satisfaction. Consistently in each state, the direct relationship between pavement quality and driver satisfaction was mediated by cognitive structure—a set of five specific beliefs motorists have about the pavement. The part of the study that ( a) applies a powerful psychological model to the task of understanding motorists’ satisfaction with pavements; ( b) offers reliable measures of driver satisfaction with pavement quality and of belief-based cognitive structure related to pavements; ( c) has accomplished the important task of identifying the most salient pavement features considered by members of the public when they evaluate pavement quality; and ( d) illustrates very clearly the importance of considering motorists’ beliefs about the pavement, issues of trust, and aspects of the Fishbein’s attitude model and Ajzen’s theory of planned behavior when trying to predict or understand driver satisfaction are covered. Although the pavement management indices used by the state departments of transportation will continue to be used to establish thresholds for improvement triggers, these indices alone do not explain such broad concepts as satisfaction with a particular pavement.
Contributing Factors of Annual Average Daily Traffic in a Florida County: Exploration with Geographic Information System and Regression Models
Authors: Zhao Fang , Chung Soon
Published: April 2007

Accurate annual average daily traffic (AADT) information is important to many applications, including roadway design, air quality compliance, travel model validation, and others. Yet complete or even extensive coverage of a network to collect traffic count data is impractical because of the cost involved. Studies have been conducted to estimate AADT for interstate highways, expressways, urban roads, and rural roads. Such efforts were often hampered by the lack of relevant detailed information that adequately explained variations in the traffic counts. A study in which geographic information system technology was extensively used to investigate various factors that may contribute to AADT on a road is presented. A variety of land-use and accessibility measurements were developed and tested. Multiple linear regression models were developed. Although most variables were statistically significant, few added enough explanatory power to be practical and useful. Four models that achieved R2 of 0.66 to 0.82 are presented. The predictive power of the models are also examined and compared.
Performance of Two Overlay Strategies Under Heavy Vehicle Simulator Trafficking
Authors: Harvey John T. , Bejarano Manuel O.
Published: April 2007

The California Department of Transportation (Caltrans) has two primary strategies for the overlay of flexible pavements: overlay with dense-graded asphalt concrete (DGAC) and overlay with asphalt rubber hot mix gap graded (ARHM-GG). Caltrans ARHM-GG overlays typically are designed to be about half the thickness of DGAC overlays for a given set of conditions. The results of a study using heavy vehicle simulator trafficking to evaluate the relative performance of the two strategies for typical California conditions and to analyze the distress mechanisms are presented. The study showed that the half-thickness ARHM designs used by Caltrans are reasonable and that the primary distress mechanism is reflection cracking. Continued hardening of the asphalt-bound and unbound layers was shown to occur in the overlaid pavements. Details of deflection studies are included.
Health Monitoring of Ironton-Russell: Bridge for Rating Purposes
Authors: Lenett Michael S. , Hunt Victor J. , Helmicki Arthur J. , Turer Ahmet
Published: April 2007

The Ironton-Russell truss bridge spanning the Ohio River between the cities of Ironton, Ohio, and Russell, Kentucky, consists of a three-span cantilever through truss with a suspended truss in the center span and a fourth span that is essentially a simple-span through truss. Visual inspections of this bridge revealed that recent welded repairs and modifications to various truss members reduced their fatigue classification as well as modified original design and construction details. When the visual inspection team identified these details along with section loss at certain truss verticals and diagonals, it was their recommendation to reduce the allowable load on the bridge from 208 260 to 26 700 N (23.4 to 3 tons). However, a 26 700-N (3-ton) load limit would hinder the transportation of heavy materials across the bridge and therefore have a severe impact on the local economy. Consequently, a series of nondestructive field tests were organized and performed on the bridge to provide better assessments of load capacity and in situ structural health. Controlled truck load tests involving resistance-based strain gauges were conducted, and an instrumented monitor utilizing low-speed (vibrating-wire) strain gauges was installed at the site. The respective data recorded during these field efforts were used not only to evaluate environmental effects on the bridge but also to compute the load rating for each of the instrumented members. The resulting objective-based load ratings and their corresponding allowable live loads greatly exceeded the recommended 26 700-N (3-ton) load limit. Essentially, objective data identified or characterized in situ structural mechanisms and therefore provided the basis for more sound and realistic load ratings.
Performance of Five-Span Steel Bridge with Fiber-Reinforced Polymer Composite Deck Panels
Authors: Reising Reiner M. W. , Shahrooz Bahram M. , Hunt Victor J. , Lenett Michael S. , Christopher Sotir , Neumann Andy R. , Helmicki Arthur J. , Miller Richard A. , Kondury Shirisha , Morton Steve
Published: April 2007

To better understand the performance of bridges with fiber-reinforced polymer (FRP) composite decks, the short-term and long-term responses of a 207-m, five-span bridge retrofitted with four different FRP panel systems were monitored through controlled truck load and modal tests at various stages and through long-term monitoring of key load-transfer mechanisms and panel responses. The overall aspects of the panel systems, connection details, construction techniques, and experimental program are presented followed by presentation of the measured responses. Key design issues (impact factors, girder distribution factors, level of composite action, and overall structural stiffness) for FRP and reinforced concrete decks are evaluated and compared against published design provisions. Performance of panel-to-panel connections and panel-to-girder connections is also discussed.
Design of Profile Wall Thermoplastic Pipe for Local Buckling
Authors: McGrath Timothy J. , Sagan Vincent E.
Published: April 2007

The results of an investigation into the local buckling capacity of profile wall thermoplastic pipe are presented. The investigation included a review of literature related to local buckling of thin sections, testing of currently available pipe, and development of a design model to predict the capacity of pipe in compression as governed by local buckling. A review of past work on the design of thermoplastic culvert pipe revealed little in the way of design methods for local buckling. The bulk of the research on buckling of thin sections has been completed by the light-gauge steel industry. A preliminary stub compression test was developed to evaluate local buckling and general capacity in compression. The results of the test correlate well with the buckling equations proposed by Winter for thin metal sections. These methods are based on the effective-width concept, which takes advantage of the capacity of a section after buckling. Design equations based on current AASHTO 50-year strength and stiffness properties have been proposed to and adopted by AASHTO. The design equations evaluate the capacity of thin sections in compression and in combined bending and compression. The check on combined bending and compression produces a limiting deflection for the field. The impact of the design method varies with the characteristics of the individual profiles produced by different manufacturers.
Debris Flow Simulation for Highway Cross Culverts
Authors: Molinas Albert , Wu Baosheng , Koester Roger D.
Published: April 2007

A study on the design of highway cross culverts in an area of potential debris flow along the Snowmass Canyon segment of SH-82 in Colorado is presented. Considering the characteristics of the drainage network and the highway cross culverts, FHWA’s BRI-STARS model is enhanced to simulate surface profiles for debris flows. Appropriate sizing of highway cross culverts is provided on the basis of the results of the model simulations for various approaches utilizing both clear-water and debris flow techniques. It is shown that the traditional clear-water modeling results in considerably undersized culverts for debris flows. The modified BRI-STARS model was verified using field data and was shown to be an effective tool in the design of cross culverts to pass debris flows across highways.
Solution Algorithm for Combined Interregional Commodity Flow and Transportation Network Model with Link Capacity Constraints
Authors: Chang Elaine , Ziliaskopoulos Athanasios , Boyce David , Waller S. Travis
Published: April 2007

A solution algorithm for the multicommodity combined freight distribution and assignment problem that computes the system optimum link flow pattern is introduced here. The distribution component of the model is based on an input-output materials balance formulation that satisfies each region’s intermediate and final demands for each commodity. An entropy term is included to capture cross-hauling and dispersion effects. The network links are assumed to be capacitated. This problem is formulated as a nonlinear program, with the nonlinear entropy term appearing in the objective function. This problem tends to be intractable even for small networks, so a Dantzig–Wolfe decomposition approach is introduced to make the problem computationally feasible. Wilson’s balancing technique is used to solve the nonlinear distribution subproblem. Test results demonstrate that realistic networks can be solved in a reasonable amount of time. The model is used to obtain insights into the trade-offs between dispersion coefficients and transportation costs on both capacitated and uncapacitated networks.
Comparison of Three Methods for Dynamic Network Loading
Authors: Astarita V. , Er-Rafia K. , Florian M. , Mahut M. , Velan S.
Published: April 2007

Interest in temporal modeling of road traffic has increased over the past decade because of the need to model traffic dynamics for the purpose of evaluating a variety of intelligent transportation components, such as traffic control measures and route guidance. Several approaches are available, including macroscopic, mesoscopic, and microscopic traffic models as well as analytical dynamic assignment models. Although microscopic models are the most detailed and realistic, they are difficult to calibrate and may not be the most practical tools for large-scale networks. Three methods for dynamic network loading that are considerably less detailed than microscopic modeling are investigated here. Each of the three methods is based on a different approach to modeling traf-fic dynamics: link-based travel time functions, the cell-transmission model, and a link-based model derived from a simplified car-following relationship. A small test network was devised, and the results from each model were compared with those obtained from a microsimulator (INTEGRATION). Interpretation of the discrepancies observed in the results gave an indication of the relative importance of the different components of the three traffic models.
Real-Time Monitoring of Subsidence Along I-70 in Washington, Pennsylvania
Authors: O’Connor Kevin M. , Clark Ronald J. , Whitlatch David J. , Dowding Charles H.
Published: April 2007

Two longwall coalmine panels were mined at a depth of approximately 156 m (510 ft) beneath I-70 east of Washington, Pennsylvania, such that the highway crossed the width of one panel at two locations. The Pennsylvania Department of Transportation (DOT) assumed responsibility for real-time monitoring of both ground deformation and changes in highway conditions. Innovative monitoring of ground deformation was accomplished with time domain reflectometry to interrogate coaxial cables installed in seven deep holes and an array of 32 tiltmeters along the highway shoulder. Surface monitoring was conducted with Global Positioning System measurements at more than 100 locations. Tiltmeters were connected to a central remote data acquisition system that automatically recorded and stored measurements. When specified tilt values were detected, the system initiated a phone call to key Pennsylvania DOT personnel, who then monitored tiltmeter measurements in real time via a phone-line connection. On the basis of this information, they could alert other agencies, if necessary, and intensify visual reconnaissance to determine if lane closures were necessary.
Safety Effects of Marked Versus Unmarked Crosswalks at Uncontrolled Locations: Analysis of Pedestrian Crashes in 30 Cities
Authors: Zegeer Charles V. , Richard Stewart J. , Huang Herman , Lagerwey Peter
Published: April 2007

Pedestrians are legitimate users of the transportation system and they should, therefore, be able to use the system safely. Pedestrian needs in crossing streets should be identified, and appropriate solutions should be selected to improve pedestrian safety and access. Deciding where to mark crosswalks is only one consideration in meeting that objective. This study involved an analysis of 5 years of pedestrian crashes at 1,000 marked crosswalks and 1,000 matched unmarked comparison sites. None of the sites in this study had a traffic signal or stop sign on the approaches. Detailed data were collected on traffic volume, pedestrian exposure, number of lanes, type of median, speed limit, and other site variables. Poisson and negative binomial regressive models were used. Study results revealed that on two-lane roads the presence of a marked crosswalk alone at an uncontrolled location was associated with no difference in pedestrian crash rate, compared with an unmarked crosswalk. Further, on multilane roads with traffic volumes above about 12,000 vehicles per day, having a marked crosswalk was associated with a higher pedestrian crash rate (after controlling for other site factors) compared with an unmarked crosswalk. Raised medians provided significantly lower pedestrian crash rates on multilane roads, compared with roads without a raised median. Older pedestrians had crashes that were high relative to their crossing exposure. More substantial improvements were recommended to provide for safer pedestrian crossings, including adding traffic signals (with pedestrian signals) when warranted, providing raised medians, and implementing speed-reducing measures.
Time Management Impacts of Pretrip Advanced Traveler Information Systems: Findings from a Washington, D.C., Case Study
Authors: Shah Vaishali P. , Wunderlich Karl , Larkin James
Published: April 2007

Numerous consumer surveys conclude that users of advanced traveler information systems (ATIS) perceive benefits foremost in travel time, followed by benefits of stress reduction and on-time arrival. Efforts by ATIS evaluators to quantify or empirically validate these benefits through field trials have yielded findings in travel time savings that are inconsistent with findings from surveys. It is hypothesized that users of ATIS benefit in the form of time management and not necessarily by reducing in-vehicle travel time. A novel approach (the simulated yoked study) is presented to evaluate the benefits to commuters from regular ATIS use. To demonstrate the simulated yoked study approach and to test the hypothesis, a case study based on travel conditions in Washington, D.C., between August 1, 1999, and October 1, 1999, was conducted. The travel experiences of commuters regularly using pretrip ATIS are simulated and compared with those of similar commuters using no traveler information before or during their commute. Findings from the case study indicate that benefits are significant in terms of on-time reliability but not in terms of the most frequently used measure of ATIS effectiveness, reduction of in-vehicle travel time. On average, regular pretrip ATIS users can reduce late arrivals by 69 percent and total late schedule delay by 72 percent compared with their counterparts. The regional reliability of the pretrip ATIS service, defined as the percentage of trips using pretrip ATIS that have arrival expectations that are met, is estimated at 77 percent. Analyses of pretrip ATIS user expectations, outcomes, and counterpart outcomes indicated that users’ perceptions of ATIS satisfaction are accurate.
Benefits Evaluation of Basic Information Dissemination Services
Authors: Thill Jean-Claude , Rogova Galina
Published: April 2007

The design and development of a library of modeling tools called ITS Options Analysis Model (ITSOAM) to evaluate the merit of intelligent transportation system (ITS) deployment elements within a benefits-cost framework are described. ITSOAM is designed as a sketch-planning tool to meet the diverse needs of New York State ITS coordinators in their economic assessment of expected user and operational benefits imputable to specific ITS elements in specific corridors. It is intended as a system assisting engineers and planners in screening worthy ITS deployments. The general modeling philosophy and framework of ITSOAM are presented, with an emphasis on the evaluation of basic information dissemination by variable message signs.
Automated Vehicle Identification Tag-Matching Algorithms for Estimating Vehicle Travel Times: Comparative Assessment
Authors: Hellinga Bruce
Published: April 2007

The computational complexity associated with three candidate automated vehicle identification (AVI) tag-matching algorithms that could be used to obtain individual vehicle travel time data in real time is examined. These algorithms are suitable for application to a linear roadway facility using transponder tags that do not have programmable memory. Analytical expressions are derived to estimate the worst-case and average computational load associated with each algorithm. A simulation is conducted to test the validity of the assumptions made in these derivations and to perform a sensitivity analysis on several key system parameters, including the rate of flow of AVI-equipped vehicles, the mean travel time between tag reader stations, the coefficient of variation of travel time, and the proportion of vehicles that pass the upstream tag readers.
Influence of Chloride Permeability Test Parameters on Results for Silica Fume and Nonsilica Fume Concrete
Authors: Abou-Zeid Mohamed , Meggers David , McCabe Steven L.
Published: April 2007

During bridge construction, an early prediction of the permeability of the concrete overlay is always desirable. However, the field-extracted rapid chloride permeability test (RCPT) specimens often have a thickness that differs from the ASTM (AASHTO) standard (50.8 mm). The need may arise to test specimens at an earlier age for an early prediction of the overlay’s performance. It has also been documented that thinner specimens may exhibit an increase in temperature during the RCPT progress. This study investigates the impact of the RCPT parameters on concrete made with and without silica fume. Silica fume and nonsilica fume concrete specimens were prepared with two compaction techniques. Test specimens were also prepared at various thicknesses and subjected to the RCPT. The coulomb charge passing each specimen was recorded every 30 min during test progress. A supplementary group of specimens was prepared 6 months later using the same constituents to strengthen some of the findings. Results reveal that the relation between the coulomb charge and specimen thickness is nonlinear. Also, strong indications exist for a possible prediction of the 56-day coulomb value for the silica fume concrete based on 28-day results and of a more-or-less trend for the coulomb value with time. Results indicate that the relation between the coulomb charge and time while testing is in general a linear one, at least for good-quality concrete. Specimen compaction technique seems to have little effect on the measured coulomb charge.
Concrete Plastic Shrinkage-Reduction Potential of Synergy Fibers
Authors: Ramakrishnan V.
Published: April 2007

The contribution of synergy fibers to plastic shrinkage reduction of concrete was studied using cement-rich concrete, and the experimental results are reported. The fiber dosages were 0.5, 1.0, and 2.0 vol% of concrete. Three different batches of concrete were made, and 15 slabs were tested. The tests were conducted using slabs 51 mm (2.0 in.) thick, 1 m (3 ft) long, and 0.6 m (2 ft) wide. The crack development was enhanced by using fans that can produce a wind velocity of 22 km/h. The performance of these fibers was compared using the crack areas of control slabs with no fibers and fiber-reinforced slabs. The results indicate that synergy fibers, at the specified dosages, tremendously reduced the plastic shrinkage in concrete. The crack-area reduction varied from 100 to 92 percent of the plain concrete. There was absolutely no cracking when a fiber dosage of 2.0 vol% of concrete was used. There was 98 percent and 92 percent reduction of plastic shrinkage cracking when the fiber dosages were 1.0 percent and 0.5 percent, respectively, by volume of concrete.
Quantifying Spatial Characteristics for Travel Behavior Models
Authors: Srinivasan Sumeeta
Published: April 2007

Land use initiatives represent a potentially effective tool for coping with the kinds of mobility patterns that North American cities face in the 1990s and in the coming century. As fine-grained data about land use and travel activity become available, they provide the opportunity to improve the understanding of the linkage between land use and transportation. The neighborhood characteristics that could affect travel behavior on the non-work tour are examined in detail. Neighborhood characteristics include land use, network, and accessibility-related characteristics quantified through the use of a geographic information system. Ultimately, such measures could be used in conjunction with detailed surveys of travel behavior to specify, calibrate, and use models of modal choice and trip type that are more sensitive to the fine-grained spatial structure of neighborhoods and transportation corridors in metropolitan areas. Microlevel data for the Boston metropolitan area, together with a 1991 activity survey of approximately 10,000 residents, provide a rich empirical basis for experimenting with relevant neighborhood measures and for simulating their effects on travel behavior. Spatial characteristics affect travel behavior even on the relatively (spatially) restricted nonwork tour and could be potentially useful for transportation planning.
Development of Microsimulation Activity-Based Model for San Francisco: Destination and Mode Choice Models
Authors: Jonnalagadda Nageswar , Freedman Joel , Davidson William A. , Hunt J. D.
Published: April 2007

A tour-based microsimulation approach to modeling destination choice and mode choice of San Francisco residents is presented. These models were developed as part of an overall tour-based travel demand forecasting model (SF model) for the San Francisco County Transportation Authority to provide detailed forecasts of travel demand for various planning applications. The models described represent two of the nine primary components of the SF model. Both model components consist of multiple logit choice models and include both tour-level models (which refer to the primary activity of the tour) and trip-level models (other activities on the tour). A separate model was estimated for each tour purpose, including work, school, other, and work-based. The destination choice models combine the trip attraction and trip distribution components of the traditional four-step process and use a multinomial logit specification. The mode choice models utilize a nested logit formulation to capture the similarities among sets of similar modes. The two models are linked by incorporating the mode choice utility logsum in the destination choice models; the result is equivalent to a nested structure with a mode choice nest under destination choice. It is demonstrated that the microsimulation approach easily allows the inclusion of a number of key variables in destination and mode choice models that have a significant explanatory power compared with those in traditional models. It is also shown that this approach allows estimation of the effects of tour characteristics on the choice of destination and mode using widely available data and estimation procedures.
Characterization and Modeling of Axial Slab-Support Restraint
Authors: Otto Rasmussen Robert , Rozycki Dan K.
Published: April 2007

Slab-support interaction has long been established as an important consideration in the design and construction of concrete pavements for streets, highways, and airfields. With the current interest in design features such as open-graded permeable bases, unbonded concrete overlays, and whitetopping pavements, the need for an accurate and standard means for characterizing this behavior is evident. With respect to conventional concrete pavements, previous studies have concluded that excessive restraint between the slab and the support layers of a pavement structure can lead to pavement distresses that are ultimately detrimental to the per formance of the pavement. These studies have indicated that undesirable restraint characteristics typically are caused by improper subbase design or construction. The consequences of underestimating or neglecting the support restraint characteristics have been shown to result in uncontrolled slab cracking, excessive joint movements, and underdesigned reinforcement. However, in some cases a high degree of slab-support restraint is desired, such as for whitetopping pavements, especially ultrathin white-topping. Recent developments in characterizing and modeling axial slab-support restraint characteristics of concrete pavements are presented. Test procedures that have been developed to accurately assess the level of axial slab-support restraint present are identified, as are future enhancements to characterization and modeling of this phenomenon.
Development of Rapid Solutions for Prediction of Critical Continuously Reinforced Concrete Pavement Stresses
Authors: Khazanovich Lev , Selezneva Olga I. , Yu H. Thomas , Darter Michael I.
Published: April 2007

A rapid solution is presented for predicting critical tensile stresses on the top surface of continuously reinforced concrete pavements (CRCP). These tensile stresses are responsible for the development of CRCP punchouts and have to be considered in a mechanistic-based design procedure. The solution is based on a combination of the neural network (rapid solution) and finite element (numerical analysis) techniques. This approach combines the convenience and computational efficiency of neural network solutions with the flexibility and power of the finite element analysis. Such a combination is quite efficient for analyzing damage accumulation in CRCP, which requires predicting portland cement concrete tensile stresses for a large number of loading and site condition combinations. The procedure for stress prediction is based on the finite element model developed with ISLAB2000. The neural network has been trained with the results from ISLAB2000. A concept developed specifically for this study—the equivalent CRCP structure—was used extensively to reduce the number of independent parameters of the neural net work and speed up its training. The proposed rapid solution provides a good match of the ISLAB2000 stress values for a small fraction of the computation cost. This makes the rapid solution CRCP a natural choice for analyzing CRCP stresses and for inclusion in a mechanistic-empirical CRCP design procedure.
Measuring Resilient Modulus of Granular Materials in Flexible Pavements
Authors: Virgil Ping W. , Yang Zenghai , Liu Chunshui , Dietrich Bruce
Published: April 2007

A comparison study from the experimental results of the falling weight deflectometer (FWD) backcalculated modulus values, laboratory-measured resilient modulus values under field and laboratory conditions, and laboratory limerock bearing ratio values for granular materials in flexible pavements is presented. Based on the measured results, a case study was conducted to illustrate the use of laboratory resilient modulus for pavement design through the AASHTO flexible pavement design procedure. The results indicated that the average laboratory resilient moduli at optimum compacted conditions were 1.1 times higher than the average laboratory determined resilient moduli under in situ conditions. The FWD backcalculated moduli were about 1.8 times higher than the laboratory resilient moduli for the granular materials. The laboratory optimum moisture content was comparable to the field-measured in situ moisture content, although the average laboratory-determined maxi mum dry density was slightly higher than the average field-measured in situ dry density. The flexible pavement design could be based on the resilient modulus values found in the laboratory.
Characterization of Asphalt Concrete Layer Interfaces
Authors: Romanoschi Stefan A. , Metcalf John B.
Published: April 2007

A new constitutive model for the asphalt concrete layer interface is proposed. Direct shear tests at four levels of normal load and three temperatures were performed on two types of asphalt concrete layer interface: with and without a tack coat. The shear stress-displacement curves determined in these tests were used to derive the constitutive model, as the tangential and normal stresses at the interface are decoupled. In the proposed model, the shear stress and displacement are proportional until the shear stress equals the shear strength and the interface fails. After failure, a friction model may be used to represent the interface condition. Three parameters were considered to completely describe the interface behavior: the interface reaction modulus K, which is the slope of the shear stress-displacement curve; the shear strength Smax; and the friction coefficient after failure μ. For the interface with a tack coat, K and Smax are not affected by the normal stress level, but they are affected for the interface without a tack coat. All three parameters of the constitutive model are temperature dependent. A testing configuration for determining the shear fatigue behavior of the interface is also described. The fatigue tests indicated a linear increase of the permanent shear displacement with the number of load repetitions, the rate of increase being higher for higher stresses. The fatigue test can be used for a comparative evaluation of the durability of different types of interfaces.
Granular Overlays on Low-Volume Roads in Washington State: Structural and Performance Characteristics
Authors: Uhlmeyer Jeff S. , Mahoney Joe P. , Lovejoy James S. , Gibson Gion E.
Published: April 2007

The granular overlay system is an alternative type of overlay for rehabilitating mostly low-volume, rural pavements. The overlay consists of a layer of densely compacted, crushed stone overlaid by a generally thin surface layer (either a bituminous surface treatment or asphalt concrete). The Washington State Department of Transportation continues to be interested in these roadways because performance has been better than expected with rehabilitation survival lives doubling from 7 to 14 years with the addition of granular overlays. Previous attempts to backcalculate layer moduli and understand the structural characteristics of granular overlays were limited because of uncertainties associated with layer thicknesses. With known layer thicknesses obtained from four sites, backcalculation of granular overlay pavements was possible. These moduli along with straightforward performance information are used to characterize granular overlays.
Impact of Partial Graduated Driver’s License Program on Teen Motor Vehicle Crashes in Kentucky
Authors: Agent Kenneth R. , Steenbergen Lorena , Pigman Jerry G. , Stinson Kidd Pamela , McCoy Carrie , Pollack Susan H.
Published: April 2007

Teen-driver motor vehicle crashes (MVCs), MVC-related injuries, and MVC-related costs before (1993-1995) and after (1997-1999) the implementation of the teen driver licensing (TDL) program in Kentucky are evaluated. Data collected as part of the study are used to recommend actions to enhance the effectiveness of Kentucky’s TDL program. The study involved the analysis of teen crash data pre-TDL and post-TDL by using data from the Kentucky Accident Reporting System database and the Kentucky Transportation Cabinet driver license file. The study also involved analysis of crash data in relation to crash costs by using the CrashCost software program. Findings indicate that implementation of the TDL program in Kentucky resulted in a substantial (32 percent) reduction in MVC rates for 16-year-old drivers from before the TDL program and a similar reduction in crashes after midnight, fatal crashes, and injury crashes for the 16-year-old age group. Cost analysis indicates an estimated annual reduction of $34.2 million in 16-year-old teen-driver MVC-related expenses. However, after a dramatic reduction in the number of crashes for ages 16 to 16.5 (learner permit stage), the number of crashes rose sharply for ages 16.5 to 17, when drivers may have progressed to independent driving. There were no decreases in crash rates for 17- and 18-year-old drivers under the TDL program. Results from this study indicate a need for more effective measures to decrease MVCs for ages 16.5 to 18, such as upgrading to a full graduated driver licensing program.
Travel Impacts of Mixed Land Use Neighborhoods in Seattle, Washington
Authors: McCormack Edward , Rutherford G. Scott , Wilkinson Martina G.
Published: April 2007

In response to suburban transportation problems, developers and planners have suggested that mixing land uses can reduce automobile dependency by making more goods and services available within walking, biking, and short driving distances. This view has resulted in a neotraditional planning movement that promotes neighborhoods designed with traditional characteristics including a mix of land uses. However, few studies have empirically explored the transportation implications for these neighborhoods. This issue is addressed by using a travel diary collected in three greater Seattle area neighborhoods characterized by neotraditional neighborhood elements including mixed land use. These data were compared with those collected in an identical diary from individuals throughout the region. It was found that residents of the mixed land use study neighborhoods in Seattle traveled 28 percent fewer kilometers (miles) than residents in adjacent areas and up to 120 percent fewer kilometers than residents in suburban areas. This trend of lower travel distances held across different socioeconomic characteristics. However, the differences in travel distances among the areas were not seen when travel time was considered. The daily travel time was about 90 min/person (including walking), regardless of where that person lived and that person’s socioeconomic status. One implication of this finding is that if a neotraditional neighborhood development does make shopping and other chores less time-consuming, there may simply be more time in the travel budget for additional regional travel. This suggests that travel from the neotraditional neighborhoods needs to be examined in a regional context.
Comparisons from Sacramento Model Test Bed
Authors: Hunt J. D. , Johnston Robert , Abraham John E. , Rodier Caroline J. , Garry Gordon R. , Putman Stephen H. , de la Barra Tomas
Published: April 2007

Three land use and transport interaction models were applied to the Sacramento, California, region by various teams of researchers. The results of these efforts were compared with each other and with the traditional transport demand model used by the regional government. The results of the modeling efforts are compared, with the focus being on how the design of the modeling frameworks and their application influenced the modeling results. A trend scenario was compared with three different policy scenarios: one that involved high-occupancy vehicle (HOV) lane construction, one that added beltway construction as well as HOV construction, and a third that involved light rail construction and limited pricing of automobile use. The results differ among the different models for the trend scenario, as well as for each model with respect to scenario-to-trend comparisons. The results show some of the limitations of aggregate models calibrated to cross-sectional data. The differences between the models provide important insight into how models should be calibrated and how their results should be used. Uncertainty in land use transport interaction models seems inevitable, and further research should investigate how such modeling frameworks should best be used to understand the influence of policy in the face of uncertain futures.
Commuter Choice Benefits Calculator: Web-Based Tool for Estimating Costs and Benefits of Commuter Programs
Authors: Herzog Erik , Grant Michael
Published: April 2007

In the transportation community, there is a real need for information and materials that will help to promote commuter benefits to employers. There is increasing recognition that these programs can offer real financial savings to employers, benefits to employees, and traffic and air quality benefits to communities. The commuter choice benefits calculator helps employers understand the costs and benefits of implementing a commuter benefits program. The calculator is designed to be simple and quick to use, requiring the user to input a modest amount of information, with defaults and ranges available for many data elements, based on studies of commuter benefits programs, to maximize ease of use. For employers, the calculator estimates costs, direct financial savings (savings realized immediately, such as tax savings), and potential financial savings (savings that require additional actions to realize, such as parking cost savings and office space cost savings). For employees, the calculator computes savings in commuting costs. For communities, the calculator estimates reduced vehicle trips, miles of travel, and emission reductions associated with commuting to work. The range of programs covered by the calculator include benefits for which federal tax incentives are available—such as employer-provided transit or vanpool benefits and parking cash-out—and benefits for which tax incentives are not available—such as telecommuting, rideshare matching, and provision of bicycle facilities. By providing information on the costs and benefits of commuter benefits, the calculator can be used as a marketing tool to promote these programs to employers.
Toll Network Capacity Calculator: Operations Management and Assessment Tool for Toll Network Operators
Authors: Zarrillo Marguerite L. , Radwan A. Essam , Dowd Joseph H.
Published: April 2007

A performance assessment tool was developed to assist managers and operators of highway networks containing toll collection facilities. The toll network capacity calculator (TNCC) quantifies a toll facility’s ability to process traffic. The calculator can also help engineers who are designing toll facilities to serve highway systems adequately. TNCC determines the maximum amount of traffic that a collection facility can handle. In addition, TNCC may be used for disruption management during lane closings, incidents, or maintenance checks. Furthermore, TNCC may be employed as a planning tool and a performance assessment tool by predicting the impact of surging traffic volumes during special events. The performance of a toll facility was determined from plaza characteristics such as lane number, lane type, and processing rates. The results of the calculations met constraints set by the characteristics of the arriving traffic. For example, variables such as the percentage of arrivals that were electronic toll collection (ETC) patrons and the percentage of arrivals that were semitrailer trucks requiring non-ETC services influenced the plazas’ performance outcome. Overflow of ETC users from the dedicated ETC lanes into the mixed lanes was also a factor. Performance was independent of hourly arrival volumes. Videotapes and transaction data at plazas provided necessary input to TNCC in the evaluation of 32 plazas on the toll network of highways in Orange County, Florida.