bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of Data-Collection Techniques for Highway Agencies
Authors: Robichaud Karen , Gordon Martin
Published: April 2007

In the last decade, many agencies within Canada and the United States have initiated programs to assess the effectiveness of their traffic-monitoring programs and the value gained from their traffic-monitoring dollars. A project was initiated by the British Columbia Ministry of Transportation to assess the accuracy of the existing traffic-monitoring system and to compare it to alternatives for estimating traffic volumes on the highway network. The study included a review of findings from similar projects by the New Brunswick Department of Transportation and the Prince Edward Island Department of Transportation and Public Works. The options for traffic data collection considered by all three provincial agencies and the accuracy and cost implications that can be expected from each option are presented. Two methods for expanding short-term traffic counts to estimate average daily traffic volumes are discussed. The reported accuracy estimates allow practitioners to better understand cost and accuracy trade-offs.
Estimating Annual Average Daily Traffic from Satellite Imagery and Air Photos: Empirical Results
Authors: McCord Mark R. , Yang Yongliang , Jiang Zhuojun , Coifman Benjamin , Goel Prem K.
Published: April 2007

Vehicles can be identified in high-resolution satellite imagery that recently has become available to the civilian community. The vehicle information contained in this imagery, and in air-based imagery, could be used in annual average daily traffic (AADT) estimation, a task conducted by many transportation agencies around the world. However, because the imagery provides information equivalent to traffic counts of very short duration, it is possible that the information is too noisy to be of use. Empirical differences between AADT estimated from 14 satellite images and air photos of Interstate segments in Ohio and the corresponding AADT estimated from traditional, ground-based estimates are presented. The distribution in differences appears relatively unbiased, implying that averaging the estimates of several images of the same segment can decrease estimate errors. The empirical errors are small enough to indicate that AADT estimation errors and ground-based sampling efforts could both be reduced by combining satellite-based data with traditional ground-based data. The differences between the image-based and the ground-based estimates are smaller in the few cases in which ground-based estimates inspired greater confidence, implying that the image-based estimates may be better than what is indicated in the distribution of differences. Evidence also suggests that the differences tend to decrease when the image leads to longer equivalent traffic count duration, indicating the potential to condition the use of the image-based data on this readily available parameter.
Preservation of Infrastructure by Using Weigh-in-Motion Coordinated Weight Enforcement
Authors: Stephens Jerry , Carson Jodi , Hult Dennis A. , Bisom Dan
Published: April 2007

The Montana Department of Transportation (DOT) has completed a pilot project in which data from a statewide network of weigh-in-motion (WIM) sensors were used to assist in scheduling weight-enforcement activities of patrol personnel. The purpose of the project was to determine if one of the division’s objectives—reducing infrastructure damage from overweight vehicles—could be better realized by using WIM data when dispatching officers. Data for the project were obtained from Montana’s state truck activities reporting system (STARS), which consists of WIM sites deployed around the state to collect information for a spectrum of Montana DOT activities. In this case, the STARS data were processed to determine the pavement damage caused by overweight vehicles each month during the baseline year. The trends identified from this analysis were used in the subsequent year to direct patrol efforts each month to the five sites that historically had experienced the greatest pavement damage from overweight vehicles. Officers were directed to the specific vehicle configurations historically responsible for the damage, as well as to their direction of travel and time of operation. During this year of WIM-directed enforcement, pavement damage from overweight vehicles decreased by 4.8 million equivalent single-axle load miles, and the percentage of vehicles operating over weight decreased by 20% across all STARS sites (both enforced and unenforced). While changes in loading patterns were observed during the enforcement activities (fewer overweight and more weight-compliant vehicles), the effectiveness of the focused enforcement in producing long-term changes in loading behaviors was uncertain.
Detecting Errors and Imputing Missing Data for Single-Loop Surveillance Systems
Authors: Chen Chao , Kwon Jaimyoung , Rice John , Skabardonis Alexander , Varaiya Pravin
Published: April 2007

Single-loop detectors provide the most abundant source of traffic data in California, but loop data samples are often missing or invalid. A method is described that detects bad data samples and imputes missing or bad samples to form a complete grid of clean data, in real time. The diagnostics algorithm and the imputation algorithm that implement this method are operational on 14,871 loops in six districts of the California Department of Transportation. The diagnostics algorithm detects bad (malfunctioning) single-loop detectors from their volume and occupancy measurements. Its novelty is its use of time series of many samples, instead of basing decisions on single samples, as in previous approaches. The imputation algorithm models the relationship between neighboring loops as linear and uses linear regression to estimate the value of missing or bad samples. This gives a better estimate than previous methods because it uses historical data to learn how pairs of neighboring loops behave. Detection of bad loops and imputation of loop data are important because they allow algorithms that use loop data to perform analysis without requiring them to compensate for missing or incorrect data samples.
Use of Long-Term Pavement Performance Data to Develop Traffic Defaults in Support of Mechanistic-Empirical Pavement Design Procedures
Authors: On Tam Weng , Von Quintus Harold
Published: April 2007

Traffic data are a key element for the design and analysis of pavement structures. Automatic vehicle-classification and weigh-in-motion (WIM) data are collected by most state highway agencies for various purposes that include pavement design. Equivalent single-axle loads have had widespread use for pavement design. However, procedures being developed under NCHRP require the use of axle-load spectra. The Long-Term Pavement Performance database contains a wealth of traffic data and was selected to develop traffic defaults in support of NCHRP 1-37A as well as other mechanistic-empirical design procedures. Automated vehicle-classification data were used to develop defaults that account for the distribution of truck volumes by class. Analyses also were conducted to determine direction and lane-distribution factors. WIM data were used to develop defaults to account for the axle-weight distributions and number of axles per vehicle for each truck type. The results of these analyses led to the establishment of traffic defaults for use in mechanistic-empirical design procedures.
Behavioral Mechanisms of Nonresponse in Mail-Back Travel Surveys
Authors: Richardson A. J.
Published: April 2007

In the conduct of sample surveys in transport, there will be some level of nonresponse. The issues of nonresponse are fundamentally connected to the questions of reducing survey bias and increasing the accuracy of sample estimates. Nonrespondents in sample surveys often have been shown to have characteristics significantly different from those of respondents. These differences are in sociodemographic characteristics and, more important, travel behavior characteristics. Issues associated with non-response to mail-back travel surveys are presented. Previous research into nonresponse in mail-back travel surveys is reviewed, in particular, methods for correcting for nonresponse. A number of alternative mechanisms for the often-observed characteristic of lower trip rates in later response waves to a mail-back survey with multiple reminders are presented. By using data from 3 years of a continuous travel survey in Melbourne, Australia, two of the mechanisms, sociodemographic effects and underreporting of trips, were extensively tested and found not to be the cause of the effect. In comparison of the remaining two mechanisms, lower actual trip rates by nonrespondents and self-selection of travel day by late respondents, a preference is expressed for the self-selection mechanism, and this is based on the results of a survey of nonrespondents and on the outcome of applying correction factors based on the two mechanisms. These results suggest that previous methods for correcting for nonresponse in mail-back travel surveys may be in error. Suggestions are made for steps necessary to fully understand the behavioral mechanisms underlying nonresponse in mail-back travel surveys.
Fuzzy-Clustering Approach to Quantify Uncertainties of Freeway Detector Observations
Authors: Ishak Sherif
Published: April 2007

Information is a key component of today’s surface transportation systems. Yet the quality of information is often determined by the quality of raw data from which it is extracted. A plethora of data is currently being compiled in real time from hundreds of miles of freeway sections nationwide. A large proportion of the data is collected via inductive loop detectors and is vital to the successful implementation of transportation data warehouses and decision support systems. Little effort has been made to establish procedures that quantify the amount of uncertainties in the traffic observations and enhance data screening algorithms. This study presents an approach derived from a fuzzy-clustering concept to measure the level of uncertainties associated with dual loop detector observations. The developed algorithm does not rely on a specific mathematical model and avoids estimating the effective vehicle length because of the limitations explained here. Based on a divide-and-conquer approach, the algorithm clusters the input space of the three traffic parameters (speed, occupancy, and volume) into regions of highly concentrated observations. The level of uncertainty in each observation can then be measured with one parameter that is derived from the membership grade and a decaying function of the normalized Euclidean distance. The parameter can thus be used for data screening as well as detector maintenance and recalibration purposes. A data screening algorithm was developed to identify erroneous observations in four sequential stages. The results obtained from screening 50,000 observations indicate that most of the noise cluttering the input space was significantly reduced by setting the uncertainty measure to 0.9.
Statistical Evaluation of Interstate 4 Traffic Prediction System
Authors: Ishak Sherif , Al-Deek Haitham
Published: April 2007

Short-term traffic prediction systems have received considerable attention in the past few years as a means to support advanced traveler information and traffic management systems. Predictive information allows transportation system users to make better trip decisions at the pretrip planning stage and en route. A comprehensive statistical analysis of the traffic prediction system performance implemented on the 40-mi corridor of Interstate 4 in Orlando, Florida, is presented. The system was evaluated under a wide range of traffic conditions and various model parameters. The prediction performance in terms of prediction errors was examined with both link-based and path-based approaches.
Automated Camera Repositioning Technique for Video Image Vehicle Detection Systems: Integrating with Freeway Closed-Circuit Television Systems
Authors: Pack Michael L. , Smith Brian L. , Scherer William T.
Published: April 2007

Transportation agencies have invested significantly in extensive closed-circuit television (CCTV) systems to monitor freeways in urban areas. While thes systems have proven to be very effective in supporting incident management, they do not support the collection of quantitative measures of traffic conditions. Instead, they simply provide images that must be interpreted by trained operators. While there are several video image vehicle detection systems (VIVDS) on the market that have the capability to automatically derive traffic measures fro video imagery, these systems require the installation of fixed-position cameras. Thus, they have not been integrated with the existing moveable CCTV cameras. VIVDS camera positioning and calibration challenges were addressed and a prototype machine-vision system was developed that successfully integrated existing moveable CCTV cameras with VIVDS. Results of testing the prototype are presentedindicating that when the camera’s initial zoom level was kept between ×1 and ×1.5, the camera consistently could be returned to its original position with a repositioning accuracy of less than 0.03 to 0.1 regardless of the camera’s displaced pan, tilt, or zoom settings at the time of repositioning. This level of positional accuracy when combined with a VIVDS resulted in vehicle count errors of less than 1%.
Evaluation of Truck Operating Characteristics on a Rural Interstate Freeway with Median Lane Truck Restriction
Authors: Mugarula Naziru , Mussa Renatus N.
Published: April 2007

The increase in truck traffic on interstate freeways continues to raise concerns about the large trucks’ dimensions that cause sight distance problems and about trucks’ low capability to accelerate, decelerate, and maintain speed particularly on steep grades. To address safety and operational concerns caused by truck traffic, a multitude of restriction policies have been instituted around the United States. This study was aimed at determining the operational and safety impacts of the 24-h restriction of trucks from using the median lane of a six-lane freeway corridor, Interstate 75 in Florida. It should be noted that traffic flow on this corridor is relatively uncongested and the corridor operates at Level of Service B or better throughout the day. Analysis of field and simulation data indicated that the difference between truck and passenger car speeds and travel times were insignificant on the unrestricted middle and shoulder lanes. About two-thirds of both passenger cars and trucks were traveling within the 10-mph pace that ranged from 70 to 80 mph in the corridor, which has a speed limit posted at 70 mph. The field data also indicated that trucks were able to use the middle lane to pass 25% of the time during the truck peak-hour period with the assumption of a 10-s gap acceptance. In addition, simulation analysis indicated that opening all lanes to trucks increased the number of lane-changing maneuvers by 11% in the daytime, a phenomenon likely to increase crashes in the corridor.
Development of Tennessee’s Freeway Service Patrol (HELP) Program
Authors: Baird Malcolm , Cove Lori , Horne Frank , Jacobs Bill
Published: April 2007

Many studies have been conducted to describe and evaluate the benefits of freeway service patrols, but much less is known about the planning and institutional development of such programs. This case study describes the implementation of Tennessee’s freeway service patrols. In 1998 the Tennessee Department of Transportation (TDOT) began planning for patrols to operate on the highest-volume freeways in the state’s four largest cities—Chattanooga, Knoxville, Memphis, and Nashville. After a staged implementation plan, TDOT has successfully implemented the patrols, known as HELP, in all four cities while also moving forward with related intelligent transportation system and incident management initiatives. Five aspects of program development are described that have been especially important to the success of the program—teamwork, attention to human resource issues, comprehensive training, first-rate vehicles and equipment, and communications.
Estimation of Truck Traffic Volume from Single Loop Detectors with Lane-to-Lane Speed Correlation
Authors: Kwon Jaimyoung , Varaiya Pravin , Skabardonis Alexander
Published: April 2007

An algorithm for real-time estimation of truck traffic in multilane freeways was proposed. The algorithm used data from single loop detectors—the most widely installed surveillance technology for urban freeways in the United States. The algorithm worked for those freeway locations that have a truck-free lane and exhibit high lane-to-lane speed correlation. These conditions are met by most urban freeway locations. The algorithm produced real-time estimates of the truck traffic volumes at the location. It also can be used to produce alternative estimates of the mean effective vehicle length, which can improve speed estimates from single loop detector data. The algorithm was tested with real freeway data and produced estimates of truck traffic volumes with only 5.7% error. It also captured the daily patterns of truck traffic and mean effective vehicle length. Applied to loop data on Interstate 710 near Long Beach, California, during the dockworkers’ lockout October 1 to 9, 2002, the algorithm found a 32% reduction in five-axle truck volume.
Modeling and Validating CORSIM Freeway Origin-Destination Volumes
Authors: Zhang Li , McHale Gene , Zhang Yunlong
Published: April 2007

In CORSIM (CORridor SIMulation) 4.32, a simplified gravity model was implemented in the freeway network to convert user input turning percentages to origin-destination (O-D) trip percentages. During the conversion, there were no O-D volume calculations or iterations to balance the destination volumes. The unbalanced destination volumes were directly converted to the turning percentages, which were different from the ones the user specified. These deficiencies in CORSIM 4.32 were corrected in the 5.0 and later versions with the procedures and methodologies described. First a linear system is introduced to obtain the O-D volumes from the entrance volumes and the ramp turning percentages, which are specified by the CORSIM user. The gravity model in CORSIM is different from the traditional gravity model in that a CORSIM user can specify certain O-D trips (in percentages) as constraints. Therefore, the O-D trip table is split into a user-specified O-D trip table and a table for the gravity model calculation. The traditional gravity model calibrates the second O-D trip table. After the O-D volumes in the second table are balanced, the joined table gives the desired results. These procedures and models replace the old CORSIM gravity model and are incorporated into CORSIM 5.0 and later versions. Because CORSIM traffic volumes from surface street interfaces are not considered in the new gravity model calculation, a procedure to manually validate and correct the O-D trip calculation is proposed. Finally, the proposed procedures were validated by cases in the CORSIM test library and by four sample cases.
Effects of Changing Occupancy Requirements for High-Occupancy Vehicle Lane: El Monte Busway Case Study, July 23, 2002
Authors: Turnbull Katherine F. , Obenberger Jon , Clark Antonette , Helou Dawn
Published: April 2007

In 1999, the California Legislature passed Senate Bill 63, lowering the vehicle-occupancy requirement on the El Monte Busway on the San Bernardino Interstate 10 Freeway from three persons per vehicle (3+) to two persons per vehicle (2+). The California Department of Transportation (Caltrans) was directed to implement this change on January 1, 2000, and to monitor and evaluate the effects of the 2+ requirement on the operation of the busway and the freeway. Based on the operational effects of the change, new legislation was approved increasing the vehicle-occupancy requirement back to 3+ during the morning and afternoon peak periods effective July 24, 2000, with a 2+ requirement at other times. Information is presented on the effect of the change in the vehicle-occupancy requirement on operation of the busway and freeway, public transit services, violation rates, accidents, and public response. The assessment is based on information from Caltrans, Foothill Transit, the Los Angeles County Metropolitan Transportation Authority, and the California Highway Patrol. Lowering the vehicle-occupancy requirement had a detrimental effect on the busway. At the same time, significant improvements were not realized in the general-purpose freeway lanes. Morning peak-period average travel speeds on the busway were reduced from 65 to 20 mph, while travel speeds in the general-purpose lanes decreased from 25 to 23 mph. Morning peak-period busway vehicle volumes increased from 1,100 to 1,600 with the 2+ designation, but the number of persons carried declined from 5,900 to 5,200. The freeway lane vehicle volumes and passengers per lane per hour remained relatively similar. Peak-period travel times on the busway increased from 20 to 30 minutes. Bus schedule adherence and on-time performance declined significantly and passengers reported delays.
Change and Clearance Interval Design on Red-Light Running and Late Exits
Authors: Schattler Kerrie L. , Datta Tapan K. , Hill Colleen L.
Published: April 2007

Red-light violations (RLV) have been an ongoing concern to many engineering professionals, because a large portion of crashes that occur at signalized intersections involve red-light running and such crashes often result in injuries and fatalities. It has been estimated that in the United States, about 260,000 traffic crashes occur per year that involve drivers who run red lights, of which 750 are fatal. A before-and-after evaluation of the impacts in terms of RLV and late exits at signalized intersections was performed with a change and clearance interval calculated according to ITE guidelines. The study included three signalized intersections located in Oakland County, Michigan. RLV data were collected with video cameras at intersection approaches before and after implementation of the change, and clearance intervals were calculated according to ITE guidelines. The results of the before-and-after study on RLV indicated mixed results. At one of the study intersections, the RLV rates were reduced after the modified change and clearance intervals were installed. However, at the other two study locations, no significant differences were found in RLV rates in the before and after periods. The rates of late exits significantly decreased after installation of the test change and clearance intervals at all three study intersections. Therefore, the effects of implemented all-red clearance intervals were effective in reducing the opportunity and risk of late-exiting vehicles being exposed to oncoming traffic at the three study intersections.
Extensions and New Applications of the Traffic-Responsive Urban Control Strategy: Coordinated Signal Control for Urban Networks
Authors: Diakaki Christina , Dinopoulou Vaya , Aboudolas Kostas , Papageorgiou Markos , Ben-Shabat Elia , Seider Eran , Leibov Amit
Published: April 2007

The objectives, approach, advantages, and some application results of recent extensions of the traffic-responsive urban control (TUC) strategy are presented. Based on well-known methods of the automatic control theory, TUC allows for traffic-responsive coordinated signal control of large-scale urban networks that is particularly efficient under saturated traffic conditions. The first version of the TUC strategy controlled only the green splits. After initial development and the first field implementations and evaluations, TUC was expanded to perform real-time cycle and offset control, and to allow for public transport priority. Simulation investigations of the extended TUC application in parts of the urban networks of Tel Aviv and Jerusalem, Israel, by use of the AIMSUN microscopic simulator demonstrate the high efficiency of the new signal control strategy.
Transit Signal Priority Along Arterials Using Advanced Detection
Authors: Wadjas Yann , Furth Peter G.
Published: April 2007

This research developed and tested the concept of advanced detection and cycle length adaptation as a strategy for providing priority for transit vehicles. In a departure from control strategies that rely on detection only a few seconds in advance of the stopline, a control algorithm was developed in which transit vehicles are detected two to three cycles in advance of their arrival at an intersection stopline, and phase lengths were then constrained so that the transit-serving phase was green for a 40-s predicted arrival window. Methods were developed for selecting whether to extend or compress phase lengths to shift a green period to cover the arrival window. Adaptive control was combined with actuated control using traffic density and queue length estimation, transit stopline actuation, and peer-to-peer communication for coordination in the peak travel direction. The method was applied by simulation to Boston, Massachusetts’ Huntington Avenue corridor, which is served by a light-rail line running partly in mixed traffic and partly in a median reservation. The prediction/adaptation algorithm resulted in 82% of the trains arriving during the green phase. This control strategy resulted in substantial improvements to transit travel time and regularity with negligible impacts on private traffic and pedestrians, and was found to be more effective than simple preemption.
Easy-to-Apply Solution to a Persistent Safety Problem: Clearance Time for Railroad-Preempted Traffic Signals
Authors: Long Gary
Published: April 2007

Traffic signals near railroad grade crossings having active warning systems are normally interconnected and receive a signal from the railroad track circuitry when trains are approaching. This train approach signal is used by the traffic signal to interrupt and preempt its normal phasing and enter into higher priority special phasings to clear the track of any vehicles that might be stopped in the pathway of a train. The amount of preemption time needed to clear a vehicle from the pathway of a train is necessary information for appropriate preemption signal settings but there are no definitive guidelines on how to determine this amount of time. It is usually left to the judgment of the signal engineer, and frequently unfounded assumptions are used. This study investigated the time required to clear a vehicle in a queue backed up onto a track at railroad-preempted traffic signals. The two key time components are start-up delay and repositioning time. Queues where all preceding vehicles are short passenger cars cause the longest start-up delays, and heavy trucks at the track involve the longest repositioning times. The model developed is convenient because once it is decided that preemption is needed, only easily determined values are required—the minimum track clearance distance, the clear storage distance, and the types of vehicles that are permitted to use the roadway. The model adopts a high level of confidence to minimize the risk of crashes but avoids the "worst-case" concept to avert an invitation for litigation when an improbable or unforeseen worst case results in a crash.
Simultaneous Optimization Formulation of a Discrete–Continuous Transportation System
Authors: Wong S. C. , Du Y. C. , Ho H. W. , Sun L. J.
Published: April 2007

Consider a city with a highly compact central business district (CBD) in which commuters’ origins are continuously dispersed. The travel demand is dependent on the total travel cost to the CBD. The transportation system is divided into two layers: major freeways and dense surface streets. Whereas the major freeway network is modeled according to the conventional discrete network approach, the dense surface streets are approximated as a continuum. Travelers to the CBD either travel on the continuum (surface streets) and then exchange to the discrete network (freeways) at an interchange (ramp) before moving to the CBD on the discrete network, or they travel directly to the CBD on the continuum. Specific travel cost–flow relationships for the two layers of transportation facilities are considered. A traffic equilibrium model is developed for this discrete–continuous transportation system in which for a particular origin no traveler can reduce his or her individual travel cost to the CBD by unilaterally changing routes. The problem is formulated as a simultaneous optimization program with two subproblems. One subproblem is a traffic assignment problem from the interchanges to the CBD in the discrete network, and the other is a traffic assignment problem with multiple centers (i.e., the interchange points and the CBD) in the continuous system. A Newtonian algorithm based on the sensitivity analyses of the two subproblems is proposed to solve the resultant simultaneous optimization program. A numerical example is given to demonstrate the effectiveness of the proposed methodology.
Impact of Travel Time Models on Quality of Real-Time Routing Instructions
Authors: Miller-Hooks Elise , Yang Baiyu
Published: April 2007

Mobile communication systems coupled with intelligent transportation systems technologies can permit information service providers to supply real-time routing instructions to suitably equipped vehicles as real-time travel times are received. Simply considering current conditions in updating routing decisions, however, may lead to suboptimal path choices, because future travel conditions likely will differ from that currently observed. Even with perfect and continuously updated information about current conditions, future travel times can be known a priori with uncertainty at best. Further, in congested transportation systems, conditions vary over time as recurrent congestion may change with a foreseeable pattern during peak driving hours. It is postulated that better, more robust routing instructions can be provided by explicitly accounting for this inherent stochastic and dynamic nature of future travel conditions in generating the routing instructions. It is further hypothesized that nearly equally good routing instructions can be provided by collecting real-time information from only a small neighborhood within the transportation system as from the entire system. Extensive numerical experiments were conducted to assess the validity of these two hypotheses.
Solving the Overlapping Problem in Route Choice with Paired Combinatorial Logit Model
Authors: Chen Anthony , Kasikitwiwat Panatda , Ji Zhaowang
Published: April 2007

Recently, there has been renewed interest in improving the logit-based route choice model because of the importance of the route choice model in intelligent transportation systems applications, particularly the applications of advanced traveler information systems. The paired combinatorial logit (PCL) model and its equivalent mathematical programming formulation for the route choice problem have been studied. An algorithm based on the partial linearization method is presented for solving the PCL stochastic user equilibrium problem. Detailed examples are provided to explain how this hierarchical logit model resolves the overlapping problem through the similarity index while still accounting for both congestion and stochastic effects in the mathematical programming formulation.
Mean-Variance Model for the Build-Operate-Transfer Scheme Under Demand Uncertainty
Authors: Chen Anthony , Subprasom Kitti , Ji Zhaowang
Published: April 2007

A mean-variance model was developed for determining the optimal toll and capacity in a build-operate-transfer (BOT) roadway project subject to traffic demand uncertainty. This mean-variance model involves two objectives: maximizing mean profit and minimizing the variance (or standard deviation) of profit. The variance associated with profit is considered as a risk. Because maximizing expected profit and minimizing risk are often conflicting, there may not be a single best solution that can simultaneously optimize both objectives. Hence, it is necessary to explicitly consider this as a multiobjective problem so that a set of nondominated solutions can be generated. In this study, the optimal toll and capacity selection for the BOT problem under demand uncertainty is formulated as a special case of the stochastic network design problem. A simulation-based multiobjective genetic algorithm was developed to solve this stochastic bilevel mathematical programming formulation. Numerical results are also presented as a case study.
Detection of Nonresilient Behavior in Pavements with a Falling-Weight Deflectometer
Authors: Orr David P.
Published: April 2007

The use of resilient models to describe the behavior of the materials in pavement design is the current standard. However, there are periods of the year when these resilient models may not be valid. Granular materials in pavements show some resiliency at every load level and moisture content. Nonresiliency is critical, however, when the plastic deformation becomes a large portion of the overall deformation in response to a load. Detection of possible nonresiliency in a pavement during use of a falling-weight deflectometer (FWD) would alert the FWD operator to possible nonresilient behavior. Two statistical checks are proposed to test for nonresiliency using the raw data provided by the FWD. Daily testing of a very weak pavement during spring thaw provided FWD data during and after a period of known nonresilient behavior. A chi-squared test of the variance may be able to detect nonresilient behavior.
Discrete and Continuous Deflection Testing of Runways at Hartsfield Atlanta International Airport, Georgia
Authors: Turner Dennis J. , Lee Jeffrey L.-J. , Stokoe Kenneth H. , Boudreau Richard L. , Watkins Quintin B. , Chang George K.
Published: April 2007

The measurement of deflection characteristics is a key feature in the evaluation of pavements. Deflections are used to evaluate pavement moduli, relative stiffness, load transfer, and, when used periodically, a rate of deterioration and remaining life. The comprehensive deflection testing program conducted on Runways 9L/27R and 8R/26L, both jointed concrete pavements, at the Hartsfield Atlanta International Airport is described. A heavy-weight deflectometer was used to measure deflections at discrete locations on slab interiors, transverse joints, longitudinal joints, and slab corners. A rolling dynamic deflectometer was used to measure continuous deflection profiles along three longitudinal lines on both runways. Before fall 2001, all pavement deflection testing was performed using a falling-weight deflectometer. Comparisons of the equipment, loading mechanisms, and measured deflections are presented.
Cohen’s Weighted Kappa Statistic in Quality Control–Quality Assurance Procedures: Application to Network-Level Contract Pavement Surface Condition Surveys in British Columbia, Canada
Authors: Landers Shawn , Bekheet Wael , Falls Lynne
Published: April 2007

Like many provincial and municipal agencies, the British Columbia Ministry of Transportation (BCMoT) contracts out the collection of pavement surface condition data. Because BCMoT is committed to contracts with multiple private contractors, quality assurance (QA) plays a critical role in ensuring that the data are collected accurately and repeatably from year to year. Comprehensive QA testing procedures for surface distress data have been developed and implemented since the data collection has been based on visual ratings with event boards. Control sites that are manually surveyed are used to evaluate whether the contractor is correctly applying the BCMoT pavement surface distress rating system. To date, the QA testing has been based on a composite-index–based criterion for assessing the level of agreement and supplemented with the detailed severity and density rating data. However, the use of a composite index presents some limitations related to the model formulation and weightings assigned to particular distress types. Although the detailed ratings are useful as a diagnostic tool to pinpoint discrepancies, in the disaggregated format, they are not conducive as acceptance criteria for QA testing. Not widely used in the field of engineering, Cohen’s weighted kappa statistic has been applied since the 1960s in other areas to assess the level of agreement beyond chance among raters. The statistic was therefore identified as a possible solution for improving the ministry’s QA surface distress testing process by providing an overall measure of the level of agreement between the detailed manual benchmark survey and the contractor severity and density ratings. The application is described of Cohen’s weighted kappa statistic for visual surface distress survey QA testing using the BCMoT survey and testing procedures as a case study.
Implementation of Automated Network-Level Crack Detection Processes in Maryland
Authors: Groeger Jonathan L. , Stephanos Peter , Dorsey Paul , Chapman Mark
Published: April 2007

The Maryland State Highway Administration (MDSHA) has collected cracking data on its roadways for use in its pavement management system since 1984. Through much of this history the pavement cracking survey was performed yearly by teams of inspectors riding in vans. With the reengineering of the administration over the years, this process began to present serious resource and logistical problems. During the past 3 years, the MDSHA pavement management group has developed and implemented a state-of-the-art automated network-level crack detection process that is showing promising results. This process is based upon the use of the automated road analyzer (ARAN) data collection vehicle, Wisecrax crack detection software, and an intensive quality-control (QC) and quality-assurance (QA) procedure. The data collection and data processing tasks are all performed in house with MDSHA resources. An overview of the processes developed and implemented by MDSHA to conduct these surveys is provided. Also discussed are challenges and lessons learned during the implementation process. Presentation of this information will allow others to gain insight into the strengths and weaknesses of adopting such a system and promote information sharing among pavement data collection organizations. Overall, it is concluded that automated network-level crack detection is a workable and efficient tool. However, a strict QC-QA regime must be instituted in order to achieve consistent and repeatable results.
Analysis Procedure for Load-Zoning Pavements
Authors: Fernando Emmanuel , Liu Wenting , Leidy Joe
Published: April 2007

Most load-zoned roads in Texas are still posted with a gross vehicle weight limit of about 260 kN, corresponding to the legal load limit at the time these roads were designed and built. Since the load from a vehicle is transmitted to the pavement through its axles, establishing load limits based on axle load and axle configuration is a more rational approach than the one currently used. In recognition of the need for a better methodology of load-zoning pavements, the Texas Department of Transportation funded a project to develop a procedure for evaluating load restrictions on the basis of axle load and axle configuration. Research efforts conducted at the Texas Transportation Institute led to the development of the Program for Load-Zoning Analysis (PLZA), which pavement engineers may use to evaluate the need for load restrictions and to determine, as appropriate, the single- and tandem-axle load limits based on a user-prescribed reliability level. To predict the induced pavement response under surface wheel loads, PLZA uses a layered elastic pavement model that permits users to characterize pavement materials as linear or nonlinear. The predicted horizontal strain at the bottom of the asphalt layer and the vertical strain at the top of the subgrade are used to evaluate pavement performance. To combine the effects of different axle loads and axle configurations, PLZA uses Miner’s hypothesis of cumulative damage to predict service life and the probability of pavement failure within a prescribed analysis period. The methodology for load-zoning is described, and its application using data collected on in-service pavements is demonstrated.
Smooth Enough?: Estimated Roughness on Roads with Low International Roughness Index Values
Authors: Dahlstedt Sven
Published: April 2007

The reported investigation is one part of a project concerning methods for measurement of the longitudinal roughness of roads and the necessary accuracy. In this study the main focus was on the subjective experience of roughness on roads with low international roughness index (IRI) values, that is, fairly good roads. With the available data it was also studied how much a random error added to the IRI values would influence the correlations with the subjective estimates. The investigation was carried out as a magnitude estimation experiment. Twenty-two observers made their estimates while traveling as passengers first in a car and later in a truck. The roughness estimates were made on 45 sections along a 60-km route. Most of the stretches had an IRI roughness between 0.5 and 3.0 mm/m, with a few of up to IRI = 5.5. The reference section had an even higher roughness, IRI = 6.24, which was given the nominal subjective roughness magnitude of 100. The main results of the study were as follows: subjective roughness seems to be a linear function of roughness according to IRI within the studied roughness range; for some road sections with a nontypical spectral composition of the road roughness, it was found that the correlation between IRI and subjective roughness decreased considerably, and the simulations of random errors added to the IRI values showed that within the studied range and with the fairly large number of observations (45), random measurement errors up to at least ±0.2 IRI unit (mm/m) can be considered insignificant.
Current Practice of Portland Cement Concrete Pavement Texturing
Authors: Hoerner Todd E. , Smith Kurt D. , Larson Roger M. , Swanlund Mark E.
Published: April 2007

The importance of surface texture characteristics to roadway safety was first recognized during the late 1940s and early 1950s when increases in traffic volumes and vehicle speeds resulted in increases in wet-weather crashes and fatalities. As a result, agencies conducted extensive research, including experimental projects around the country, to better understand and improve the surface conditions of portland cement concrete pavement in wet-weather conditions. As new surface-texturing methods were tried and evaluated, pavement engineers recognized that a general trade-off existed between friction and noise; that is, surface textures with higher friction tended to produce greater tire-pavement noise. Although considerable information exists on the influence of surface friction characteristics on safety and tire-pavement noise, it is dispersed among numerous sources. An effort is made to identify and summarize key texture-related information and recommendations based on the current state of the practice. Specifically, pavement texture nomenclature is introduced, methods of measuring and quantifying texture are discussed, traditional and innovative texturing methods and techniques are described, respective conclusions pertaining to the influence of texture characteristics on surface friction and tire-pavement noise are summarized, and current state-of-the-art texture-related recommendations are provided.
Acceptability of Pavement Roughness on Urban Highways by Driving Public
Authors: Shafizadeh Kevan , Mannering Fred
Published: April 2007

The driving public’s attitude toward acceptable levels of road roughness is explored using empirical data collected on urban highways. Individual driver acceptability levels are matched with international roughness index (IRI) levels to examine the existence of potential user acceptability thresholds. In particular, the observed trends are compared with the federal IRI guideline of 170 in./mi (2.7 m/km) for acceptable ride quality recommended by FHWA in its 1998 strategic plan for the National Highway System. The research reported on appears to provide empirical support for the federal IRI guidelines that are already in existence. This study also found that IRI levels provided a very good indication of driver acceptability, which agrees with past research based on antiquated present serviceability ratings.
Development of Test Methodology and Model for Evaluation of Curing Effectiveness in Concrete Pavement Construction
Authors: Jeong Jin-Hoon , Zollinger Dan G.
Published: April 2007

Early-age moisture loss from the surface of a concrete pavement may induce undesirable effects that play a factor in long-term performance. Early-age detrimental behavior such as slab curling, warping, delamination, and even plastic shrinkage cracking are affected by the amount of evaporation and the effectiveness of the curing medium. The rate of evaporation is a key item in the monitoring of the quality of the curing. However, most approaches for this are largely empirical and are useful only under laboratory conditions. The effective curing thickness concept is introduced as a method to evaluate the effectiveness of a curing method. The surface relative humidity has the biggest influence on both the effective curing thickness and the rate of evaporation. Thus, prediction of the rate of evaporation of the water from concrete depends on the relative humidity of the surface and is important for evaluation of the curing method. Existing evaporation models, including the American Concrete Institute nomograph, were evaluated for their capabilities in predicting evaporation from curing concrete. Data from a series of laboratory experiments with a modified version of Penman’s evaporation model are also presented.
Application of Infrared Imaging and Ground-Penetrating Radar to Detect Segregation in Hot-Mix Asphalt Overlays
Authors: Sebesta Stephen , Scullion Tom
Published: April 2007

Segregation is a serious problem in hot-mix asphalt and typically results in poor performance, poor durability, a shorter life, and higher maintenance costs for the pavement. A summary of the results and recommendations from three projects in Texas in which infrared imaging and ground-penetrating radar were used to examine the uniformity of the pavement mat is presented. Both techniques have significant advantages over currently used nuclear density techniques in that they provide virtually 100% coverage of the new surface. The effectiveness of both the infrared and radar techniques was evaluated by taking measurements on new overlays at the time of placement, coring, and then identifying relationships between changes in the infrared and radar data with changes in the measured volumetric and engineering properties of the cores. Analyses of the results showed that changes in both infrared and radar data are significantly related to changes in hot-mix asphalt properties such as air void content and gradation. On the basis of current Texas Department of Transportation specifications, significant changes in the hot-mix asphalt are expected if temperature differentials of greater than 25°F (13.9°C) are measured after placement but before rolling. If the surface dielectric of the in-place mat changes by more than 0.8 for coarse-graded mixes and 0.4 for dense-graded materials, significant changes in mix properties are expected. Given the promising results from this work, agencies should consider implementing both the infrared and ground-penetrating radar technologies.