bluuebunny/crossref_metadata_2025 huggingface dataset:
In Situ Evaluation of Layer Stiffnesses of Airport Pavements by Crosshole Seismic Tests
Authors: Lee Ngar-Kok James , Stokoe Kenneth H. , McNerney Michael T. , McCullough B. Frank
Published: April 2007

Many runways and taxiways in major international airports have been in service for 20 years or more. To manage this pavement system effectively, it is important to determine existing pavement conditions and to predict remaining service life. These two aspects are some of the challenges facing airport and highway engineers alike. By knowing the rate of change since the commissioning of the runway, one may be able to predict the remaining life of the pavement. Optimizing the useful life of the pavement is an effective way of managing the pavement and maximizing the benefit of the capital investment. To evaluate existing pavement conditions at the Dallas–Fort Worth (DFW) International Airport, a testing procedure was used that had been developed at The University of Texas at Austin using seismic waves. This procedure involves performing crosshole seismic tests with a system tailored to perform independent measurements in all layers of the pavement profile, that is, independent stiffness measurements in the surface, cement-treated base, and lime-stabilized subbase layers as well as the subgrade. The cross-hole procedure proved to be very effective for measurements of both runway and taxiway pavements. The test procedure, field equipment, and test results are presented herein. Issues considered in the study include how each layer stiffness has changed with more than 20 years of service at DFW; what is the relative stiffness change in each of the layers between trafficked and untrafficked areas; and how have the stiffnesses of the different layers beneath the joints changed relative to these same layers beneath the midslab areas.
Time-Dependent Permanent Deformation Models for Asphaltic Mixtures
Authors: Qi Xicheng , Witczak Matthew W.
Published: April 2007

Over the past two decades, a variety of permanent deformation models have been developed to predict rutting in asphalt pavements. Because all of these models are normally based upon laboratory tests in which very short loading and rest times are used, they may not reflect the true actual loading and rest times that may occur in the field service condition. To overcome this limitation, a research study was funded by the Maryland State Highway Administration at the University of Maryland to develop a universal permanent deformation model that could account for both loading and rest times upon its cyclic load behavior. A laboratory testing program was conducted using the cyclic creep test on a single asphalt mixture. The variables considered in the testing program were loading and rest times, both at three levels, and temperature and stress, each at two levels. Two replicate tests per cell were also used, resulting in a total of 72 test specimens being evaluated. Based on the lab test results, two types of empirical permanent deformation models have been calibrated. It was found that the empirical model coefficients, intercept and slope, and permanent deformation parameters, μ and α, were affected by both loading and rest times. Predictive equations were developed for the intercept, slope, μ, and α. The empirical permanent deformation models developed account for both loading and rest times at multiple temperature and stress levels.
Evaluation of Michigan 70-mph Speed Limit
Authors: Binkowski Sarah E. , Maleck Thomas L. , Taylor William C. , Czewski Tamara S.
Published: April 2007

On August 1, 1996, the speed limit on certain sections of Michigan freeways increased from 104.6 to 112.6 km/h (65 to 70 mph). This was due to the Michigan Legislature passing a bill that permitted the governor of Michigan to increase the speed limit given that a study be conducted to determine the effects on safety and capacity. Michigan State University conducted the study that determined the effects of increasing the speed limit on certain sections of highway. This study examined not only freeways that were increased to 112.6 km/h (70 mph), but also the speeds and capacities of freeway sections where the speed limit was not increased. Different types of speed analyses were done in comparing the test sections where the speed limits were raised with the control sections where the speed limits were not raised. The analysis also included categorizing the roadway into intercity and recreational routes to determine the effect on speeds for different uses in road use. The speed data also were broken down into different vehicle types. A preliminary accident analysis was performed on the control and test sections to determine the effect of increasing the speed limit on accidents. It was proved that increasing the speed limit on certain sections of freeway in Michigan had little effect on the change in speed and capacity on both test and control sections.
Freight Energy Use Disaggregated by Commodity: Comparisons and Discussion
Authors: Vanek Francis M. , Morlok Edward K.
Published: April 2007

The analysis of energy consumption in freight transportation is almost always approached by disaggregating overall energy consumption by mode, which then provides a basis for understanding trends and underlying factors that influence them and for developing conservation policies. Another important approach is to disaggregate by commodity, because it is commodity flows that generate the modal vehicle flows and hence the modal energy consumption in transportation. Thus changes in energy use by commodity are important factors in understanding trends in energy consumption and may provide a basis for energy conservation policies centered on industries using transportation. Total freight energy consumption is estimated for a range of commodity groups using an activitybased approach to energy consumption, where total freight activity is decomposed into components by mode and by commodity group, and then each component is multiplied by an intensity estimate to calculate total energy use for that commodity group. Two important findings are discussed: ( a) commodity groups with high energy growth between 1972 and 1993 had a combination of substantial ton-mile growth and modal shift to truck, and ( b) commodity groups of finished products with a high average value per ton in general have a much higher average freight energy intensity than raw materials with a low average value per ton.
Development of an Aggregate Fuel Consumption Model for Signalized Intersections
Authors: Liao Tsai-Yun , Machemehl Randy B.
Published: April 2007

An aggregate model to estimate intersection fuel consumption is developed, and the effects of signal timing on fuel consumption are investigated. A conceptual framework is proposed to identify interrelationships among traffic characteristics, signal control strategies, and roadway geometric conditions. On the basis of the framework, an Analytical Fuel Consumption Model (AFCM) is developed to estimate fuel consumption at signalized intersections. The AFCM, based on considerations of vehicle operating conditions, describes how fuel is consumed on three street segments (inbound approach, intersection itself, and outbound leg) for three signal cycle stages (the effective red time, queue departure time t0, and remaining green time). Numerical experiments are conducted to test the AFCM estimation capability and to investigate the effects of signal timing on fuel consumption. Results of numerical experiments are compared with results from the TEXAS simulation model using two criteria: differences of total fuel consumption and correlation coefficients of elapsed fuel consumption. Results from the TEXAS model are within 10 percent of those from the AFCM, and the elapsed fuel consumption is highly correlated. This indicates that total fuel consumption estimated from the AFCM is very close to the results from the TEXAS model, which suggests that the mathematical representations of the AFCM might be used to replace the simulation-based model. Moreover, the results from these experiments indicate that total fuel consumption with respect to signal cycle time at signalized intersections possesses a convex pattern, and the optimal cycle length for minimization of fuel consumption can be obtained.
Light-Duty Diesels: Consumer Perspectives and U.S. Energy Supply Issues
Authors: Moore J. S. , Maples J. D. , Patterson Philip D.
Published: April 2007

An assessment of the potential for diesel engine light-duty vehicles to reduce petroleum consumption and greenhouse gas emissions is presented. Historical diesel vehicle sales behavior is presented and analyzed. Future market penetration and resultant petroleum consumption and emission reductions for advanced diesel engines are projected. Results of a survey of new vehicle buyer attitudes toward improved diesel engines are presented and analyzed. Effects of increased diesel market share on diesel fuel supply and price are estimated. Overall, the outlook for diesels in light vehicles is somewhat promising if pollution issues and consumer concerns about the earlier diesels can be addressed.
Fuel-Cycle Energy and Emissions Effects of Tripled Fuel-Economy Vehicles
Authors: Mintz Marianne M. , Wang Michael Q. , Vyas Anant D.
Published: April 2007

Estimates of the full fuel-cycle energy and emissions effects of lightduty vehicles with tripled fuel economy (3X vehicles) as currently being developed by the Partnership for a New Generation of Vehicles are presented. Seven engine and fuel combinations were analyzed: reformulated gasoline, methanol, and ethanol in spark-ignition, direct-injection engines; low-sulfur diesel and dimethyl ether in compression-ignition, direct-injection engines; and hydrogen and methanol in fuel-cell vehicles. Results were obtained for two market share scenarios. Under the higher of the two scenarios, the fuel-efficiency gain by 3X vehicles translated directly into reductions in total energy demand, petroleum demand, and carbon dioxide emissions. The combination of fuel substitution and fuel efficiency resulted in substantial reductions in emissions of nitrogen oxide, carbon monoxide, volatile organic compounds, sulfur oxide, and particulate matter smaller than 10 microns (PM10) for most of the engine-fuel combinations examined. The key exceptions were diesel- and ethanol-fueled vehicles, for which PM10 emissions increased.
Practice-Oriented Approach to Developing a Data Requirements Model for Bridge Condition Assessment
Authors: Sanford Kristen L. , McNeil Sue
Published: April 2007

Data collection activities in the bridge management process have not been designed. Rather, they have evolved over time, creating inconsistencies within and between agencies in data collection methods, data items collected, data quality, and data uses. The development of a data requirements model for bridge condition assessment, based on an investigation of the state of the practice and the desired state, is described. Using data flow diagrams and influence diagrams as structuring tools, a process has been developed that an agency can use to assess and improve its data collection practices.
Development of Distress Progression Models Using Panel Data Sets of In-Service Pavements
Authors: Madanat Samer , Cheol Shin Hee
Published: April 2007

Pavement distress progression models predict the extent of a distress on pavement sections as a function of age, design characteristics, traffic loads and environmental factors. These models are usually developed using data from in-service facilities to calibrate the parameters of mechanistic deterioration models. The data used for the statistical estimation of such models consist of observations of pavements for which the distress has already appeared. Unfortunately, common statistical methods, when applied to such data sets, produce biased and inconsistent model parameters. This type of bias is known as selectivity bias, and it results from the fact that less durable pavement sections are over-represented in the sample used for model estimation. A joint pavement distress initiation and progression model, consisting of a discrete model of distress initiation and a continuous model of pavement progression is presented. This approach explicitly accounts for the self-selected nature of the sample used in developing the progression model, through the use of appropriate correction terms. Moreover, previous research is extended by accounting for the potential presence of unobserved heterogeneity in the model, which is related to the use of a panel data set for model estimation. This is achieved by using a random effects specification for both the discrete and continuous models. An empirical case study demonstrates the application of this approach for highway pavement cracking models.
Update of Long-Term Pavement Performance Manual Distress Data Variability: Bias and Precision
Authors: Rada Gonzalo R. , Wu Chung L. , Elkins Gary E. , Bhandari Rajesh K. , Bellinger William Y.
Published: April 2007

Pavement distress surveys based upon field interpretation and manual mapping and recording of the distress information on paper forms has been used in the Long-Term Pavement Performance (LTPP) program to collect important pavement condition and distress data. Although this manual method was used in the past as a backup to the 35-mm black and white photographic-based method, recently the use of manual distress survey methods has increased in intensity and coverage. To promote uniformity and consistency of distress data collection, one of the early LTPP efforts was to develop standard definitions, measurement procedures and data collection forms. Various quality control and quality assurance functions have also been implemented to provide for high quality data. However, despite these efforts, manual surveys are still based upon a single rater’s subjective classification of distresses present in the field. Recognizing that rater variability exists, a study was undertaken by FHWA to assess the level of variability between individual distress raters and to address the potential precision and bias. Results from nine LTPP distress rater-accreditation workshops conducted during the period of 1992 to 1996 were used as the source of data. Analyses of those data led to numerous observations and conclusions regarding the bias and precision of LTPP distress data. Because LTPP distress data are to be used in the development of pavement performance prediction models, it is believed that the level of variability found in this study should be reduced to increase its potential usage in the development of such models. A number of recommendations to improve the variability associated with manual distress surveys data are included.
Contracting for Pavement Distress Data Collection
Authors: Smith Roger E. , Freeman Thomas J. , Pendleton Olga J.
Published: April 2007

Many agencies responsible for managing pavements have adopted pavement management systems (PMS) to help manage their pavement networks more cost-effectively. One of the most costly parts of operating a PMS is collecting condition information, especially pavement distress information. Many agencies have started to contract for pavement distress data collection. Some of the agencies have experienced problems with the data collected by contract. A study for agencies in Washington and Oregon to define the accuracy of data needed by the agencies with an evaluation of certain participating vendors using semiautomated data collection methods is described. Issues about quality control and quality assurance faced by agencies considering contracting for automated data collection also are raised. These issues need additional study to develop appropriate guidelines. The initial set provided is based on discussions with some of the agencies currently contracting for pavement distress data collection.
Assessment of Long-Term Pavement Performance Plan Wall Projection-Based Distress Data Variability
Authors: Raja Shekharan A. , Rada Gonzalo R. , Elkins Gary E. , Bellinger William Y.
Published: April 2007

In the Long-Term Pavement Performance (LTPP) program, 35-mm, black and white, continuous-strip photographs are used as a permanent record of pavement distress development for archival purposes and to quantify the distress severity and extent for pavement performance analysis. The traditional method of interpreting distress from LTPP film utilizes a relatively small image projected onto a digitizing tablet. From quality control checks performed on the interpreted data, it was found that some low severity types of distress, identified from larger magnified images projected onto a wall or projection screen, could not be seen in the smaller image used for distress interpretation. The variability in distresses interpreted directly off of the large format, wall-image projection was assessed through analysis of interpretations performed on six asphalt concrete and six portland cement concrete pavement sections used in the LTPP distress rater accreditation workshops. The data set included distress ratings from eight individuals, four two-person rater teams, and an experienced rater team. Also available were distress ratings performed in the field by the experienced rater team, which are used as reference values which represent the best estimate of ground-truth. Statistical tests show that the film-interpreted distresses from individual raters exhibit much larger variability than those from the rating teams. The most significant contributor to this finding is outlier observations in which one of the individual raters had significantly different ratings than the rest of the group. The spread in the rating teams was much lower. The film interpreted distresses from the experienced group correlated very well with the field-derived reference values.
Comparative Study of Ride Quality Measuring Devices
Authors: El-Korchi Tahar , Collura John
Published: April 2007

State highway agencies (SHAs) in New England have an ongoing interest in providing the public with smoother rides. As an incentive to contractors, some SHAs include a bonus and penalty clause for new construction based on profile measurements and smoothness indices. These states are considering the use of high-speed profilers for profile measurements and quality control/quality assurance implementation. Therefore, an assessment of the accuracy and repeatability of these devices is essential. A comparative study of high-speed profilers owned by the New England SHAs was conducted in Worcester, Massachusetts. Two sites were profiled using the dipstick and the high-speed profiling devices. Statistical analysis of International Roughness Index measurements were used for evaluation of precision and bias, profiler speed, and sensor type. The repeatability for the profilers was good, especially for combined wheel paths (standard deviation between 0.016 and 0.079 m/km). The accuracy for the profilers varied depending on profiler type.
Linear Acceleration Car-Following Model Development and Validation
Authors: Aycin M.F. , Benekohal R.F.
Published: April 2007

A linear acceleration car-following model has been developed for realistic simulation of traffic flow in intelligent transportation systems (ITS) applications. The new model provides continuous acceleration profiles instead of the stepwise profiles that are currently used. The brake reaction times of the drivers are simulated effectively and are independent of the simulation time steps. Chain-reaction times of the drivers are also simulated and perception thresholds are incorporated in the model. The preferred time headways are utilized to determine the simulated drivers’ separation during car-following. The features of the model and the realistic vehicle simulation in car-following and in stop-and-go conditions make this model suitable to ITS, especially to autonomous intelligent cruise-control systems. The car-following algorithm is validated at microscopic and macroscopic levels by using field data. Simulated versus field trajectories and statistical tests show very strong agreement between simulation results and field data.
Improved High-Order Model for Freeway Traffic Flow
Authors: Liu Guoqing , Lyrintzis Anastasios S. , Michalopoulos Panos G.
Published: April 2007

An improved high-order continuum model is developed based on hyperbolic conservation laws with relaxation, linearized stability analysis, and more realistic considerations of traffic flow. The improved high-order model allows smooth traveling wave solutions as well as contact shocks (different densities moving at the same speed), is able to describe the amplification of small disturbances on heavy traffic, and allows fluctuations of speed around the equilibrium values. Furthermore, unlike existing high-order models, it does not result in negative speeds at the tail of congested regions and disturbance propagation speeds greater than the traffic flow velocity because the improved model has a zero characteristic speed and a nonnegative characteristic speed that is equal to the traffic flow velocity. The relaxation time is a function of density and, in the equilibrium limit, the improved high-order model is consistent with the simple continuum model. The improved high-order model is compared with the simple continuum model. Exemplary test results suggest that the improved high-order model is intuitively correct. Comparison of numerical results with field data suggests that the improved high-order model yields lower error levels than the simple continuum model.
Modeling Multiple User-Class Traffic
Authors: Hoogendoorn Serge P. , Bovy Piet H. L.
Published: April 2007

In contemporary traffic flow theory, the distinction between user classes is rarely made. However, we envisage that the accuracy and the descriptive power of the macroscopic traffic flow models can be improved significantly by separating user classes and their specific flow characteristics. As a consequence, the possibility of improved estimation and prediction of traffic flow conditions becomes available. Additionally, the availability of a realistic multiple user-class traffic flow model enables the automated generation of user-dedicated traffic control policies by means of mathematical optimal control theory. A macroscopic multiple user-class model is derived from mesoscopic principles. In opposition to earlier multiple user-class models, the model presented here implicitly defines equilibrium relationships between traffic density and equilibrium velocities as a function of current traffic conditions, traffic composition, and distribution of user-class-dependent desired velocities. Additionally, the velocity variance variable is introduced describing deviations from the average speed within the user classes. The multiple user-class model identifies competing processes. On the one hand, drivers attempt to traverse the freeway at their desired velocity; on the other hand, they adjust their velocity because of interaction with slower vehicles. These processes can result in self-formation of apparently random local structures. Finally, the proposed model satisfies the anisotropy condition and the invariant personality condition.
Comparison of INTEGRATION, TSIS/CORSIM, and WATSim in Replicating Volumes and Speeds on Three Small Networks
Authors: Wang Yuhao , Prevedouros Panos D.
Published: April 2007

INTEGRATION, TSIS/CORSIM, and WATSim can simulate traffic operations on mixed arterial and freeway networks. Comparisons are presented here using three small networks in Honolulu for which detailed, simultaneous, and contemporaneous flow conditions are known. The models produced reasonable and comparable results on most network links. Of the three software programs, only INTEGRATION can simulate U-turns, but it also is least able to model complex signal operations. TSIS/CORSIM is best at replicating lane-changing behavior, but its percentile input for off-ramps is both inconvenient and inaccurate. WATSim needed the least calibration for producing good results, but its animation is inferior and its capacity-based car-following parameters are undesirable. The default parameters off all three software programs never offered satisfactory results.
Forecasting Short-Term Freight Transportation Demand: Poisson STARMA Model
Authors: Garrido Rodrigo A. , Mahmassani Hani S.
Published: April 2007

A framework for analyzing, describing, and forecasting freight flows for operational and tactical purposes is presented. A dynamic econometric model is proposed. This model incorporates the spatial and temporal characteristics of freight demand within a stochastic framework. The model was applied in an actual context and its performance was compared with standard time series models (benchmark) for forecasting ability. The proposed model outperformed the benchmark from the econometric viewpoint. Extensive diagnostic checking and sensitivity analysis confirmed the robustness of the modeling methodology for short-term forecasting applications.
Practical Approach to Model Trip Chaining
Authors: Shiftan Yoram
Published: April 2007

The need to model trip chaining has been discussed widely in the travel demand literature, but new approaches generally have been limited to academic research. Trip chaining was modeled in an actual urban area model. The model was developed for Boise, Idaho, on the basis of a household survey of 1,600 households. For this model, a tour was defined as a sequence of trip segments that start at home and end at home. The model distinguishes between two main types of tours: A tour that includes one or more work destinations is defined as a work-related tour (WRT); all other tours are defined as nonwork-related tours (NWRT). A model system was developed by assuming the hierarchy of the model components. The highest-level model estimates auto ownership for the household. On the basis of auto ownership, the frequency of WRT is estimated, and on the basis of the frequency of WRT, the frequency of NWRT is modeled. These three model components produce the number of WRT and NWRT for each household. All subsequent models are estimated at the tour level. The WRT model system includes work destination choice model, tour type model including the number of stops on the way to and from work and midday trips, and secondary destination choice model for all nonwork destinations. The NWRT model was developed in the same way with some structural differences.
Link-Nested Logit Model of Route Choice: Overcoming Route Overlapping Problem
Authors: Vovsha Peter , Bekhor Shlomo
Published: April 2007

A new link-nested logit model of route choice is presented. The model is derived as a particular case of the generalized-extreme-value class of discrete choice models. The model has a flexible correlation structure that allows for overcoming the route overlapping problem. The corresponding stochastic user equilibrium is formulated in two equivalent mathematical programming forms: as a particular case of the general Sheffi formulation and as a generalization of the logit-based Fisk formulation. A stochastic network loading procedure is proposed that obviates route enumeration. The proposed model is then compared with alternative assignment models by using numerical examples.
Optimal Routing of Hazardous Materials in Stochastic, Time-Varying Transportation Networks
Authors: Miller-Hooks Elise , Mahmassani Hani S.
Published: April 2007

The selection of routes in a network along which to transport hazardous materials is explored, taking into consideration several key factors pertaining to the length of time of the transport and the risk of population exposure in the event of an incident. That travel time and risk measures are not constant over time and at best can be known with uncertainty is explicitly recognized in the routing decisions. Existing approaches typically assume static conditions, possibly resulting in inefficient route selection and unnecessary risk exposure. Several procedures for determining superior paths for the transport of hazardous materials in stochastic, time-varying networks are presented. These procedures and their extensions are illustrated systematically for an example application using the Texas highway network. The application illustrates the tradeoffs between the information obtained in the solution and computational efficiency, and highlights the benefits of incorporating these procedures in a decision-support system for hazardous material shipment routing decisions.
Evaluation of Dynamic Fleet Management Systems: Simulation Framework
Authors: Regan Amelia C. , Mahmassani Hani S. , Jaillet Patrick
Published: April 2007

The problem of dynamic fleet management for truckload carrier fleet operations is introduced, and the principal elements of a simulation framework for the evaluation of dynamic fleet management systems are described. The application of the simulated framework to the investigation of the performance of a family of real-time fleet operational strategies, which include load acceptance, assignment, and reassignment strategies, also is described. The simulation framework described is an example of a first-generation tool for the evaluation of dynamic fleet management systems. Selected experimental results are highlighted. These are intended to illustrate some of the issues encountered in real-time fleet management and the role of the simulation modeling environment in investigating them.
Determining Impact of Road Lighting on Motorway Capacity
Authors: Van Goeverden Cees D. , Botma Hein , Bovy Piet H. L.
Published: April 2007

The subject of this paper is the impact of road lighting on the capacity of uninterrupted motorway sections. A capacity estimation method was used that is based on extrapolation of the free-flow part of the fundamental diagram representing the relation between flow rate and density. The method assumes that the density at capacity is not affected by illumination, which implies that capacity shifts are fully the result of speed changes. The method was applied in a Dutch case study. In a before-and-after study, the impact of road lighting was estimated for two directions of one road section. Capacities of the road section were estimated for various periods of the day. Capacities during the daytime did not differ significantly before and after introduction of lighting. Nevertheless, during nighttime a significant increase in capacity of about 2.5 percent was found.
New Estimation Technique for Vehicle-Type-Specific Headway Distributions
Authors: Hoogendoorn Serge P. , Bovy Piet H. L.
Published: April 2007

Recently, a new statistical procedure was developed that enables fast, accurate, and robust estimation of composite headway distributions, such as Branston’s generalized queueing model (GQM). Until now, the new procedure had only been applied to aggregate vehicular flow. In this paper, the estimation procedure is extended to headway observations segregated according to vehicle type and period of the day. Consequently, the parameters of a new mixed-vehicle-type headway distribution model based on Branston’s headway model can be estimated. Distinction of vehicle type and sample periods provides additional insight into the plausibility of the headway distributions and parameter values, as well as into the car-following behavior of the distinct vehicle classes varying across the different periods. The estimation procedure was applied to traffic data collected on a two-lane rural road in the Netherlands. Comparison of the estimated headway distributions with real-life data shows that headway distributions can be realistically replicated with the Pearson-III-based mixed-vehicle-type GQM. Inter-pretable differences between the morning, noon, and evening sample periods and between passenger cars, unarticulated trucks, and articulated trucks are found. In addition, passenger-car equivalents for both articulated trucks and unarticulated trucks were determined from the parameter estimates.
Estimation of Percentage of Delayed Vehicles Based on Traffic Variables for Rural Highways
Authors: Romana Manuel G. , Lépez Gemma
Published: April 2007

According to the Highway Capacity Manual (HCM), it is possible to quantify level of service for rural highways using a basic parameter: percent time delay. Since this variable cannot be measured, it is proposed in the HCM that the percentage of delayed vehicles (% DV) be used as a surrogate measure. The manual gives no means of predicting or estimating % DV other than a curve relating total % DV to total hourly volume. However, it is worth noting that the methodology proposed in the manual does not use this curve. In any case, there has been to this date no proposal as to the estimation of % DV by traffic direction. The results of an attempt to estimate % DV by direction through multiple correlations are presented. The data were gathered on four highways in the province of Madrid, Spain (M-111, M-501, M-600, and M-607). Measurements were carried out in 3-h periods on plain or slightly sloping ground during daily or weekly peak periods. The average daily traffic and rate of heavy vehicles in 1991 were, sorted chronologically, 9,500 and 6.4 percent for M-607; 9,800 and 5.1 percent for M-600; 8,100 and 8.6 percent for M-111; and 14,400 and 5.0 percent for M-501. Several multiple correlations are offered, and one is chosen that has an accuracy of 0.7964, expressed through the coefficient r2 (the explained variation). The model is % DV (Direction 1) = A * (VDirection1) + B * (VDirection2) + C, with the following numerical values: % DV = 0.0443 * V1 + 0.0096 * V2 + 25.5411.
Background for HCM Section on Analysis of Performance of Roundabouts
Authors: Troutbeck Rod
Published: April 2007

The background to the Highway Capacity Manual (HCM) section on the analysis of the performance of roundabouts is discussed. The paper has two main objectives: to discuss the background of different techniques used to evaluate the level of service and to describe the method included in the HCM. The paper is in two parts. In the first part, the first objective is addressed and the parameters needed to predict both delay and capacity, which in turn are used to evaluate the level of service, are described. It is concluded that the gap acceptance approach is a reasonable one when the performance of roundabouts is predicted using data from uncongested sites. If there are a significant number of roundabouts with congested approaches, an empirical model should be used. It is also concluded that the results from one country cannot be immediately transferred to another. In the second part of the paper, the recommended practice included in HCM Chapter 10 is given.
Field Measurement of Signalized Intersection Delay for 1997 Update of the Highway Capacity Manual
Authors: Powell James L.
Published: April 2007

The 1997 update of the Highway Capacity Manual changes the basis of delay for level-of-service determination at signalized intersections from stopped delay to conceptually more appealing total delay. Total delay is made up of components including volume, control, and geometric delay. Level of service is now defined in terms of control delay, which provides a more stable and tractable relation to total delay, but the issue of field measurement remains in any case. A combined theoretical and empirical approach to measuring field delay on the basis of typical vehicle deceleration and acceleration profiles is taken in this paper. The profiles are related to the relatively easily surveyed quantity of vehicles in queue, which is equivalent to estimating time in queue of all vehicles stopped by the traffic signal. The results indicate that after vehicles in queue are sampled, correction factors can account, in practical terms, for the unsurveyed deceleration and acceleration delay. The corrections are simple additive factors that are a function of free-flow speed and average number of vehicles stopped in queue. Another adjustment is included for the consistent tendency of human observers to overestimate vehicles in queue. All of these factors are included in the new 1997 HCM procedure for measuring signalized intersection delay in the field. Further identified work includes the need to fully develop the total delay concept to account for geometric delay consistently over a variety of interrupted- and uninterrupted-flow facilities. Such resolution should be included in HCM 2000 preparation currently in progress.
Phase Capacity Characteristics for Signalized Interchange and Intersection Approaches
Authors: Bonneson James A. , Messer Carroll J.
Published: April 2007

Described in this paper are the development, calibration, and application of models that collectively can be used to predict the saturation flow rate and start-up lost time of through movements at signalized interchange ramp terminals and other closely spaced intersections. These models were calibrated with data collected at 12 interchanges. It is concluded that saturation flow rate decreases as the distance to the downstream queue decreases. This queue is formed by the signal at a downstream intersection. Saturation flow rate increases with traffic pressure, as quantified by traffic volume per cycle per lane. It is recommended that an ideal saturation flow rate of 2,000 passenger-car units per hour of green per lane be used for signalized ramp terminals and other high-volume intersections in urban areas. The data collected for this research indicate that start-up lost time increases with saturation flow rate.
Extension and Application of Prosser-Dunne Model to Traffic Operation Analysis of Oversaturated, Closely Spaced Signalized Intersections
Authors: Messer Carroll J.
Published: April 2007

Traffic congestion continues to have a serious impact on the productivity of the nation’s transportation system. Signalized arterials and service interchanges in urban areas serve as critical surface street facilities. These facilities often experience serious congestion problems because of high traffic demands that exceed capacity and also because of their common, closely spaced intersections and ramp terminals. Moreover, service interchanges are usually part of a signalized cross arterial and also may have short spacings to adjacent signalized intersections. Major deficiencies exist in the analysis technology and software tools available for analyzing potential traffic congestion problems at signalized arterials and service interchanges having closely spaced ramp terminals. This paper presents extensions of work originally published by Prosser and Dunne in Australia for analyzing the operational impacts of queue spillback on the capacity and delay of closely spaced signalized intersections. Coding of the described algorithm into FORTRAN was conducted, followed by experimental testing of the model using a calibrated version of the microscopic computer simulation program TRAF-NETSIM. Satisfactory comparisons were obtained between the initial version of the newly developed Prosser-Dunne Extended (PDX) model and NETSIM, but more testing and enhancement of the PDX model are recommended before implementation in existing operational software packages is considered.
Simple, Generalized Method for Analysis of Traffic Queue Upstream of a Bottleneck
Authors: Erera Alan L. , Lawson Tim W. , Daganzo Carlos F.
Published: April 2007

An approach is generalized for enhancing a standard input-output diagram to represent graphically the time and distance that vehicles spend in a queue upstream of a bottleneck. The approach requires the construction of a curve depicting the cumulative number of vehicles to have reached the back of the queue as a function of time. The original technique, described in a previous paper, is reviewed for bottlenecks with constant capacity and for those where capacity changes once. The approach is then generalized to allow multiple changes in bottleneck capacity, and the original assumption of a triangular flow-density ( q-k) relation is relaxed to one that is piecewise-linear concave. Although it is consistent with the kinematic wave theory of traffic flow, the proposed approach is simpler to apply to complex problems because it avoids the laborious construction of a time-space diagram. It allows the estimation of several measures required in the evaluation of the impacts of bottlenecks, including the (accurate) number of vehicles in queue and the physical extents of queues at any time and the total time spent by vehicles in different traffic states.
Vertical Contraction Scour at Bridges with Water Flowing Under Pressure Conditions
Authors: Arneson Larry A. , Abt Steven R.
Published: April 2007

One of the areas of bridge scour estimation technology that hydraulic engineers, researchers, and scientists generally agree needs more understanding is what happens to the bottom of the channel under a bridge when the low chord becomes inundated and the flow through the opening changes from free surface flow to pressure flow. The vast majority of what is known about local scour in bridge openings has been derived for bridges with water flowing with a free surface. The literature shows that no previously conducted research is capable of being used to predict the component of vertical contraction scour that would be encountered under a full range of sediment transport conditions. In an attempt to fill part of this gap in the field of bridge scour estimation technology, a comprehensive program was developed to investigate pressure flow scour in bridge openings. Data were collected so that a relationship could be developed to predict the scour that would occur across the channel as a result of a vertical flow contraction. An equation is presented that can be used to estimate the magnitude of vertical contraction scour that could occur at a bridge with water flowing under pressure conditions. The equation presented has a coefficient of determination of 0.89 and has readily obtainable independent variables. In addition to the equation that can be used to estimate the magnitude of vertical deck scour that may occur, techniques and guidance that could be applied by the practicing hydraulic engineer to estimate the effects of pressure flow conditions on local scour in bridge openings are also presented.
Development and Testing of a Partial Exfiltration Trench for In Situ Treatment of Highway Drainage
Authors: Sansalone John J. , Smithson Joseph A. , Koran Joseph M.
Published: April 2007

Urban roadway drainage often contains high concentrations of anthropogenic metal elements, solids, and organic compounds. Metal elements and solids accumulate on the pavement surface between precipitation events and are transported to surficial soils, receiving waters, and ground-water by pavement drainage. A report is provided on the design and performance of a bench-scale and prototype in situ control strategy, called a partial exfiltration trench (PET). The PET serves as a modification to the current practice of pavement underdrainage, providing a water quality function, in addition to water quantity control. The water quality modification functions by immobilizing infiltrated metal elements within the PET. The PET utilizes sand modified with an oxide coating (OCS). Bench-scale PET simulations were utilized to evaluate PET feasibility and breakthrough capacity. Results indicate OCS capacity for zinc, cadmium, lead, and copper was significantly improved as the pH increased from 6.5 to 8.0. Based on characteristic metal loadings from urban Cincinnati pavement drainage, bench-scale PET performance indicates that the design life of a PET may exceed 15 years in a humid climate. Performance of a prototype PET installed along an urban Cincinnati highway indicates metal element mass removal efficiency is generally greater than 80 percent after nearly 1 year of pavement drainage loadings.
Rail-Highway Grade Crossing Consolidation in Kansas
Authors: Russell E. R. , Mutabazi M. I.
Published: April 2007

Consolidation or closure of unnecessary grade crossings is a cost-effective but difficult-to-achieve option for increasing the safety of highway-rail grade crossings. Consolidation not only needs traffic engineering expertise, it also needs the support of local government officials and citizens. It is as much a public relations effort as an engineering exercise. To win local support, proposals for closing selected crossings should appear reasonable to the public, that is, the public should be able to see a need or net benefit. A corridor study is more effective than targeting single crossings for closure. Selecting a corridor with high-potential closure candidates can be the key to the success of winning local approval. Finding the most “hazardous” crossings can help select high-potential corridors. The development of a model to pinpoint Kansas’ best candidates for closure as a key step in selecting corridors where consolidation efforts should be concentrated is described.
Driver Behavior at Rail-Highway Crossings
Authors: Abraham John , Datta Tapan K. , Datta Sue
Published: April 2007

A study of driver behavior at 37 rail-highway crossings in Michigan revealed the possible association between past crash histories and violations. Data collection included recording license plate numbers for violating vehicles, driver gender, approximate age of the driver, and the vehicle make and model. Driver violations were categorized into five different levels of severity ranging from routine to critical. The 37 study sites were subdivided into four groups based on crossing geometry and traffic control. The number of sites in the groups ranged from 5 to 18. Seven years of crash data on the study sites were considered for significance testing. Observed violation data for the same groups were calculated, and tests for statistical significance were performed on them. The results of this study indicated promise for the use of the violation data in determining the relative hazardousness of rail-highway crossings in combination with crash histories. The violation data may also be used to develop countermeasures that would help alleviate violations and eventually traffic crash problems at rail-highway crossing sites. Targeted enforcement as well should assist in driver behavioral modifications. Additionally, the timely arrival of trains after the warning devices are triggered is an essential element that motorists assess when considering taking risks.
Trapped Vehicle Detection System for Four-Quadrant Gates in High Speed Rail Corridors: Design Methodology and Implementation Issues
Authors: Coleman Fred , Moon Young J.
Published: April 2007

The objective of this paper is to determine the location of sensors in the track system functioning as checkpoints to provide information to a train on the status of the crossing and provide evasive maneuver time for the train and trapped vehicle. Two train-operating scenarios are evaluated: the first provides no deceleration when a trapped vehicle is detected; the second scenario has the train decelerate at a tolerable deceleration rate to passengers when a trapped vehicle is detected. The findings indicate that there is a trade-off between minimizing the distances to locate the trapped vehicle detection sensors in the track system and potential issues of reliability of vehicle detection and maximization of safety. Recommendations include provision of on-board real-time status information on the crossing(s) in the train with automatic train location and control to continuously provide safe stopping distances in event of a trapped vehicle.