bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Speed-Flow Relationship Under Congested Conditions on a Freeway
Authors: Zhou Miao , Hall Fred L.
Published: April 2007

The purpose of this work is to investigate the relationship between speed and flow within congestion, that is, the lower portion of the standard curve, and in particular to identify an equation to describe this portion of the relationship. Data were obtained for Toronto, Ontario, from the Gardiner Expressway RESCU System and the Highway 401 COMPASS System. The data were first screened to remove dubious data points and observations that were from transitions between congested and uncongested conditions. They were then analyzed using regression analysis for four types of function: quadratic, cubic, exponential, and power. The principal findings related to the shape of the speed-flow curve within congestion are as follows. It is important to utilize data from a full range of flows in order to fit a curve to represent the congested part of the speed-flow curve. To obtain this range, data from several sites may be needed. Despite the combination of sites, there is often what might be termed a “data gap” between easily available congested data (up to perhaps 1,800 vphpl) and flow rates for queue discharge flow. When data for that gap are available, the speeds under congested conditions seem to increase fairly rapidly at high congested flows. There appears to be a difference in the speed-flow relationship among different freeways and under construction conditions on one of them. If there are different curves for different freeways (or free-flow speeds) for the top half of the speedflow relationship, it seems reasonable that there might also be for the bottom half. However, it also appears to be the case that downstream conditions such as construction can affect the speed-flow curve itself at an upstream location. This makes sense in that operations within the queue are governed by the downstream queue discharge, but it is a change from what one expects for the other two segments of the speedflow curve.
Estimating Free-Flow Speeds for Rural Multilane Highways
Authors: Dixon Karen K. , Wu Chi-Hung , Sarasua Wayne , Daniel Janice
Published: April 2007

The National Highway System Designation Act of 1995 repealed the national maximum speed limit. As a result, many of the states have increased posted speed limits to 105 km/h (65 mph) for select multilane highways. This study evaluates the distribution of the speed and studies the influence of site characteristics, light conditions, and type of vehicle on the field-measured free-flow speed. The suitability of the Highway Capacity Manual multilane highway rules of thumb for freeflow speed to both an 89- and a 105-km/h (55- and 65-mph) posted speed limit condition is also discussed.
Queueing Model To Determine Variability of Recurrent Congestion at Freeway Link over a Year
Authors: Botma Hein
Published: April 2007

Since about 1990 the quality of road traffic operation on Dutch freeways is no longer expressed as a level of service, but in the percentage of vehicles that experience congestion and in terms of their delay. The criterion for an optimal congestion percentage refers to the overall value for all working days of a year. This overall percentage is determined by means of a deterministic queueing model that simulates a year’s traffic operation. A simplified version of this model is presented in this paper. It takes into account systematic and random fluctuations in traffic demand and roadway capacity. Demand is a function of the month of the year, the day of the week, and the hour of the day, and it has a random fluctuation. Capacity changes because of light and weather conditions and also has a random component. The extent to which several sources of variation contribute to the overall percentage of vehicles experiencing congestion is analyzed as well as the total delay and the delay per vehicle involved. Moreover, the day-to-day variation of several congestion characteristics and their dependencies are discussed.
Method for Estimating Capacity Reduction in High-Occupancy-Vehicle Lane Ingress and Egress Sections
Authors: Xu Guan , Huang X. Peter , Pant Prahlad
Published: April 2007

In high-occupancy-vehicle (HOV) facility design, there are concerns about the impacts of merging and weaving movements at the ingress and egress (I/E) sections of a barrier-separated freeway HOV lane. Weaves and merges can disturb traffic flow and cause freeway capacity reduction at HOV-lane I/E sections. Such capacity reductions can cause bottlenecks that could eventually reduce the benefit of an HOV lane. An impact analysis regarding capacity reduction is necessary, which can improve HOV-lane operations by leading to reasonable design options that minimize the capacity reduction. This study developed a method for estimating the capacity reductions at freeway HOV-lane I/E sections under various geometric and operating conditions, which is an effective tool for HOV facility planning, design, and operations analysis. The study first identified the major factors that affect freeway HOV-lane I/E section capacity. Then it explored the relationship between capacity reduction and the impact factors on the basis of a database developed from field collection and a freeway simulation model. Finally, the study developed an applicable equation for estimating capacity reduction using nonlinear regression with a third-order polynomial format. The equation was tested through a case study, the results of which indicate that the equation can yield reasonable results, satisfying the 95 percent confidence interval, in capacity reduction estimation.
Comparison of Car-Following Models for Simulation
Authors: Aycin M. F. , Benekohal R. F.
Published: April 2007

Presented in this paper are the car-following methods and algorithms of the NETSIM, INTRAS, FRESIM, CARSIM, and INTELSIM models. Moreover, the car-following performance of these models is compared with the field data. NETSIM, INTRAS, FRESIM, and CARSIM car-following models first move the leader and then update the follower in one simulation time step. Because of this approach, these car-following models cannot be used to command vehicles in real-time intelligent transportation systems applications. Moreover, brake reaction times are limited by the simulation time step because of this method of updating the vehicles. INTELSIM was developed to overcome these deficiencies. INTELSIM moves vehicles simultaneously and produces solutions for a continuous time frame. INTELSIM produced the best agreement with the field data and required the least amount of calibration effort.
On-Line Monitoring System for Real-Time Traffic Management Applications
Authors: Doan Dung Le , Ziliaskopoulos Athanasios , Mahmassani Hani
Published: April 2007

This paper is concerned with the problem of on-line monitoring of a traffic network. The problem was motivated by the need of real-time dynamic traffic assignment systems to maintain an internal representation of the traffic network consistent with that of the actual network. Potential error sources that can cause inconsistencies between the internal and the actual state of the network are identified and classified. The issues of observability and state variable definition of traffic networks are discussed. A framework for a monitoring system is sketched that aims to maintain a representation of the state of a network consistent with that of the actual network by applying on-line and off-line adjustments. Some solution approaches and computational results are presented for the main modules of the framework.
Application of Subset Autoregressive Integrated Moving Average Model for Short-Term Freeway Traffic Volume Forecasting
Authors: Lee Sangsoo , Fambro Daniel B.
Published: April 2007

Traffic volume is one of the fundamental types of data that have been used for the traffic control and planning process. Forecasting needs and efforts for various applications will be increased with the deployment of advanced traffic management systems. With the importance of the short-term traffic forecasting task, numerous techniques have been utilized to improve its accuracy. The use of the subset autoregressive integrated moving average (ARIMA) model for short-term traffic volume forecasting is investigated. A typical time-series modeling procedure was employed for this study. Model identification was carried out with Akaike’s information criterion. The conditional maximum likelihood method was used for the parameter estimation process. Two white noise tests were applied for model verification. From the analysis results, four time-series models in different categories were identified and used for the one-step-ahead forecasting task. The performance of each model was evaluated using two statistical error estimates. Results showed that all time-series models performed well with reasonable accuracy. However, it was observed that the subset ARIMA model gave more stable and accurate results than other time-series models, especially a full ARIMA model. It is believed that the use of a subset ARIMA model could increase the accuracy of the short-term forecasting task within time-series models.
Analyzing System Travel Time in Arterial Corridors with Unconventional Designs Using Microscopic Simulation
Authors: Reid Jonathan D. , Hummer Joseph E.
Published: April 2007

Recent studies have identified the median U-turn (MUT) design as having potential for improving intersection stopped delay at isolated intersections. This study was an effort to quantify the reductions in travel time and other critical traffic operation measures of effectiveness for the MUT and super-street median (SSM) geometric designs over a system of signals compared with the traditional two-way left-turn lane (TWLTL) design. The key function of the MUT design is removal of all left-turn movements at signalized intersections, creating two-phase signal operations and increased progression opportunities. The SSM design allows perfect progression of through traffic in both directions because signals on both sides of the arterial can operate independently. The analysts constructed models of a typical suburban arterial corridor near Detroit, Michigan, in CORSIM according to a fixed external-node coordinate system and fixed origin-destination volumes. These allowed an equitable systemwide comparison of measures of effectiveness between the arterial designs. An analysis of variance determined the importance of arterial geometry related to total system time, average stops per vehicle, and average speed. Results showed that the MUT and SSM designs improved system travel time and average speed compared with the TWLTL design. Analyzing geometry as a function of the time of day showed that the MUT and SSM alternatives significantly reduced system travel time and increased average speeds during the a.m. and p.m. peak hours and showed very similar results compared with the TWLTL design during off-peak conditions. The authors recommend that engineers analyzing alternatives for arterials similar to that tested consider the MUT and SSM designs.
Multilayer Artificial Neural Networks for Level-of-Service Analysis of Signalized Intersections
Authors: Saito Mitsuru , Fan Jianzhong
Published: April 2007

The effects of architecture, learning mode, and learning rate on the performance of a level-of-service (LOS) analysis model using an artificial neural network (ANN) are discussed. Multilayer LOSANN models demonstrated improved quality of learning and testing over single-layered models in evaluating level of service of signalized intersections given geometric, traffic, and traffic signal control data. At present, LOSANN takes delay data from Highway Capacity Software (HCS) outputs; hence its accuracy is constrained by the accuracy of the HCS analyses. However, if delays can be determined directly by field observation, the relationships (or patterns) between field-measured delays and the traffic, geometric, and signal control conditions can be fed to LOSANN. Then the neural network-based model can evaluate the level of service at a higher level of accuracy, and such models can be used as part of advanced traffic management systems to automate LOS analyses.
Modeling Heterogeneous Traffic Flow
Authors: Khan Sarosh I. , Maini Pawan
Published: April 2007

The composition of traffic in developing countries is mixed, with a variety of vehicles, motorized and nonmotorized, using the same right-of-way. The motorized or fast-moving vehicles include passenger cars, buses, trucks, auto-rickshaws, scooters, and motorcycles; nonmotorized or slow-moving vehicles include bicycles, cycle-rickshaws, and animal-drawn carts. The proportion of slow-moving vehicles in the traffic stream may vary from 10 to 80 percent. Since the 1950s, considerable research has been done to develop traffic flow models for roadways with mainly motorized vehicles or homogenous traffic, representing the composition of traffic primarily in industrialized countries. A review of the literature has shown that limited studies have been done to develop an understanding of traffic flow for non-lane-based heterogeneous or mixed traffic conditions in developing countries. Some efforts have applied a variation of practices developed for homogenous traffic by converting heterogeneous traffic to equivalent passenger-car units and then applying procedures for homogenous traffic. However, these efforts have produced mixed results. A comprehensive review is presented of the few studies on mixed, non-lane-based traffic in India, Bangladesh, and Indonesia. The unique characteristics of traffic composition, driver behavior, roadway geometry, maneuverability, and vehicular interactions are also presented. Most of the studies conducted in this area are not often readily available. This paper, therefore, should serve as a good reference.
Freeway and Arterial Traffic Flow Simulation Analytically Embedded in Dynamic Assignment
Authors: Jayakrishnan R. , Chen Anthony , Tsai Wei K.
Published: April 2007

This paper is an extension of earlier work on dynamic traffic assignment with an analytically embedded traffic flow simulation. Previously, a modified Greenshields’ speed-density relationship was used to derive a link travel time function that is monotonically increasing and convex with respect to density. It was recognized that this link travel time function is more applicable for freeway traffic than for arterial street traffic, where a large portion of travel times occurs at the nodes as a result of queueing. In this paper a version of the model is developed with explicit queueing links to simulate such traffic conditions on an arterial street network. The dynamic traffic assignment problem is formulated in a two-level optimization framework, separating the temporal and spatial variables into two problems. The lowerlevel problem represents an equilibrium traffic assignment model that solves the spatial variables subject to a set of feasible paths fixed by the temporal estimates from the upper-level problem. The upper-level problem determines the temporal variables by finding the minimum time-dependent travel times from the origin to all other nodes, assuming equilibrium traffic loads assigned from the previous lower-level problem to be fixed. A set of recursive equations is derived to compute the link traversal times that satisfy the first-in, first-out requirement. An iterative solution algorithm using small time steps with queueing links is developed to solve the proposed two-level dynamic traffic assignment problem. Results are also provided to show the effects of embedding a traffic simulation with explicit treatment of queues to capture traffic dynamics on arterial streets.
Numerical Simulation and Analysis of Traffic Flow
Authors: Zhang H. M. , Wu T.
Published: April 2007

Six finite-difference equations often used to approximate the continuity equation of traffic flow are compared in terms of their ability to solve the Lighthill-Whitham-Richards model. Ten representative initial traffic flow conditions were selected, and numerical solutions were obtained for the selected cases using the six finite-difference equations. Results are compared with analytical solutions, and the numerical properties of these approximations are examined. It was found that the upwind finite-difference schemes with volume corrections (Godunov-type schemes) produce the best results for all 10 cases and are reasonable finite-difference schemes for simulating traffic flow.
Preprocessor Feature Extractor and Postprocessor Probabilistic Output Interpreter for Improved Freeway Incident Detection
Authors: Abdulhai Baher , Ritchie Stephen G.
Published: April 2007

Automated incident detection algorithms usually utilize direct measurements of traffic volumes and occupancies as input and output binary indications of the traffic status for every time step. The transferability of such algorithms is often poor because of the extensive overlap between the incident-related cluster and the incident-free cluster of patterns in the input space. The observed overlap is not only significant but also location specific. The extent of the overlap is shown, its causes are discussed, and an input preprocessor is proposed that relies on modifying the input feature space in order to segregate the two clusters of patterns and reduce their overlap. The result is a more readily separable set of classes; easier classification of new patterns, which leads to better performance; and most important, less site-dependent performance and hence significantly better direct transferability of the detection algorithm with less need for retraining at new sites. On the output side, isolated binary algorithm outputs also have several drawbacks that are identified. An output postprocessor is proposed that links the isolated outputs using a Bayesian update process and converts the isolated outputs into a continuous probabilistic measure that is updated for every time step. The output at one interval is therefore used as a prior probability for the next. The preprocessor and the postprocessor proposed in this paper were developed as integrated components of a universally transferable freeway incident detection framework, UNITID, but are generally applicable to any similar incident detection system.
Impact of Intelligent Cruise Control on Motorway Capacity
Authors: Minderhoud Michiel M. , Bovy Piet H. L.
Published: April 2007

The introduction of driver support systems such as (autonomous) intelligent cruise control (ICC) is foreseen within a few years. However, it is still uncertain how these systems will affect traffic-flow characteristics on motorways. A simulation study has been conducted to assess the impacts on roadway capacity more precisely. Ten different ICC designs are investigated and compared with a reference situation without such support systems. The equipment penetration rates of the systems studied varied and were 10, 20, 50, to 100 percent. A capacity analysis was performed for a common bottleneck situation: an on-ramp to a two-lane motorway. On the basis of the simulation results, some unexpected findings emerged. Support systems that support the driver at all speeds and that do not restrict the deceleration level give rise to capacity gains of about 12 percent. However, the first-generation ICC systems will hardly increase traffic-flow performance. A special stop-and-go ICC design did not improve the traffic-flow quality. It was found that, regardless of the ICC type, a headway setting of 1.2 s did not change roadway capacity near an on-ramp bottleneck significantly.
Intelligent Transportation Systems Planning in a Medium-Sized, Relatively Uncongested Urban Area
Authors: Kane Tom , Maze T.H. , Pearce Vincent P.
Published: April 2007

The Des Moines Area Metropolitan Planning Organization (MPO) completed an early deployment study for the Des Moines, Iowa, metropolitan area in late 1997. The purpose of the study was to develop a strategic plan for intelligent transpotation systems (ITS) deployment and to provide initiative for the development of an ITS infrastructure. When FHWA sponsored the Des Moines metropolitan area’s early deployment study, Des Moines was the smallest metropolitan area to undertake such a study. Therefore, there were no similarly sized urban areas from which to draw examples. Furthermore, although the metropolitan area and traffic volumes are growing, congestion is not seen as a significant problem in Des Moines. As a result of minimal traffic congestion, there was and is some skepticism among the transportation stakeholders in the need for ITSs. The development of an ITS infrastructure is seen as even more problematic when the capital requirements for ITS must compete with the capital requirements of other, traditional transportation improvements. Despite the initial skepticism regarding the need for ITS and the ability to afford ITS, Des Moines-area transportation stakeholders have become very supportive of the initiatives identified in the plan. The generation of support for an ITS was developed through two galvanizing issues. The first was a focus on the safety benefits of an ITS as opposed to congestion reduction benefits. The second was to focus on the use of an ITS to mitigate the impacts of the reconstruction of I-235. I-235 cuts across Des Moines, running through the north side of the central business district, and has been the single most important factor in forging commuting and development patterns in the Des Moines area. As a result, arterial streets that parallel I-235 will be greatly affected by the diversion of traffic from I-235, which is likely to occur during reconstruction. An ITS’s ability to manage traffic under dynamic conditions provided an incentive for transportation stakeholders to rally behind the ITS strategic plan. The process used to develop the plan and review the plan’s recommendations is discussed. One of the issues that the plan attempts to address is the identification of technology appropriate for an urban area the size of Des Moines.
Understanding the Transportation Policy Process: Intelligent Transportation Systems Through Two Conceptual Lenses
Authors: Lindquist Eric
Published: April 2007

An alternative to transportation policy making, the agenda-setting framework, which is more realistic than the rational-comprehensive perspective of policy making traditionally taught to and applied by engineers and planners, is presented. In general, this framework for analysis suggests that before a policy decision is made, two important processes are at work: agenda setting and the selection of alternative solutions. The process of setting the agenda focuses attention on certain issues instead of others, whereas the selection of alternatives focuses attention on certain solutions instead of others. These processes are nonlinear, dynamic, and contrary to much of what is expected from the rational-comprehensive model. These two competing perspectives are outlined, and the rise of intelligent transportation system technologies as solutions for transportation problems is used as an illustration of the agenda-setting perspective.
Metropolitan Model Deployment Initiative: A Learning Experience
Authors: Peterson Christine , Colvin Tisha , Moy Nancy
Published: April 2007

The U.S. Department of Transportation’s creation of a new initiative for integrated approaches to transportation management and the provision of traveler information services for metropolitan areas is explored and evaluated from a unique vantage point. The Metropolitan Model Deployment Initiative (MDI) was executed through a first-time solicitation for MDI applications. Twenty-three proposals were received for the program launch. Focusing on the 19 nonselected or progress teams, the authors conducted lengthy interviews with 55 team members. These interviews revealed and detailed the challenges and obstacles that these teams faced in each stage of their response to the new initiative. More than the response experiences of the progress teams are explained, however. The candor and insights of the team members are used to make recommendations. With the passage of the Transportation Equity Act for the 21st Century and the legislative expansion of the deployment initiative to metropolitan and rural areas, MDI is likely to continue, and recommendations for effective expansion are articulated. Understanding of new program initiations from a different source of input for use as a guide to both responders and program creators is discussed. Team dynamics, the need for clarity and examples, careful adherence to schedule, and a varied array of support activities were findings that can be generalized beyond the MDI experience to new transportation program initiatives regardless of mode. Whether programs are new or continuing, a learning cycle that contains an opportunity for all participants to share their challenges, problems, and suggestions with FHWA-FTA promises to be a source of refinement and improvement.
What Advanced Traveler Information System Information Do Users Want? Evidence from In-Vehicle Navigation Device Users
Authors: Raj Mehndiratta Shomik , Kemp Michael A. , Lappin Jane E. , Brand Daniel
Published: April 2007

Findings from research into user preferences for enhanced travel information disseminated to the drivers of private vehicles are reported. The research is based on trade-off surveys of three small populations in the Seattle, Chicago, and Boston metropolitan regions who had had significant hands-on experience with vehicles equipped with dynamic invehicle navigation (IVN) units in prior field operational tests. It was found that the structure of consumers’ preferences was similar across the three surveys. The analysis indicates that, at least in a familiar commuting context, users are split in their opinions whether they prefer to receive routing advice or simply advice about traffic delays to inform their own routing decisions. More people prefer the latter, although this is less pronounced for women than for men. Geographical coverage of routes and the frequency of information updates were found to be significantly important attributes of IVN information. The results also indicate diminishing returns in user values for information improvement. At least at this stage of market development, respondents valued the basic enhancements in coverage and update frequency more than they valued further refinements.
Transportation Operations Coordinating Committee System for Managing Incidents and Traffic: Evaluation of the Incident Detection System
Authors: Mouskos Kyriacos C. , Niver Edip , Lee Stuart , Batz Tom , Dwyer Peter
Published: April 2007

The Transportation Operations Coordinating Committee’s System for Managing Incidents and Traffic (TRANSMIT) is an operational test that uses vehicles equipped with tags of the E-ZPass electronic toll collection system as traffic probes for traffic surveillance and incident detection. The TRANSMIT incident detection algorithm is based on statistical comparison of real-time estimates of travel times with continuously updated historical travel times for the same time period of the day and type of day (weekday, Saturday, Sunday, or holiday). The probability of detecting an incident and the false-alarm rates produced by TRANSMIT during a 4-month evaluation period (January to April 1996) may be considered excellent for the data collected on the New York State Thruway and satisfactory for the data collected on the Garden State Parkway. The mean time to detection of an incident was not estimated at this stage of the evaluation. The TRANSMIT communication system exhibited excellent performance in terms of the transmission rates systemwide, which were found to be near 100 percent. Only the radio link at Tappan Zee Bridge exhibited a lower transmission rate. A limited probe vehicle test was conducted to determine the detection rate at individual roadside terminals. The lower detection rates observed were site specific rather than systemwide. The performance of the TRANSMIT incident detection algorithm performed very favorably compared with the performances of the best incident detection algorithms reported in the literature.
Toward a Consumer Demand–Driven Intelligent Transportation System Policy: Findings from Southern California
Authors: Wells Kimberly , Horan Thomas
Published: April 2007

As part of a 3-year research initiative, Claremont Graduate University Research Institute researchers developed a survey to assess public attitudes toward intelligent transportation systems (ITSs) as both a consumer choice and a public policy issue. The substantive focus included advanced traveler information systems (ATISs) and vehicle safety products (safety devices). Specific survey goals included ( a) a description of travel behavior and traffic information use, ( b) gauging of attitudes toward ATISs and safety devices, and ( c) an exploration of attitudes toward ITS-related public policies. The questionnaire was administered via a computeraided telephone interview to a sample of randomly selected Southern California residents during the fall of 1997. Results from analysis of the 610 responses suggest that although many travelers currently obtain traffic information, most do not seem to use this information in any proactive sense to avoid congestion. Once congestion is encountered, participants in general simply await its abatement. Respondents portrayed interest in ATIS products but overall were more intrigued by safety devices. Travelers with long commutes expressed both the least satisfaction with current traffic information and the strongest interest in ATISs. Overall, women displayed greater interest in ITSs than men and younger respondents revealed more interest than their older counterparts. Results from public policy questions indicate support for ITSs and an inclination to support tax allocations for its development. However, almost half of the survey participants also expressed concern over the potential negative individual privacy implications of ITS deployment.
Incorporating Neural Network Traffic Prediction into Freeway Incident Detection
Authors: Teng Hualiang , Martinelli David R. , Taggart Benjamin T.
Published: April 2007

Because of their superior capabilities in emulating nonlinear systems, neural network models have been applied to traffic prediction with various degrees of success. However, these neural network-based traffic prediction models have not been used for incident detection. On the other hand, it is expected that the performance of an incident detection algorithm can be improved if an advanced prediction model is used. The development of several traffic prediction models that were then integrated into incident detection algorithms is documented. The traffic prediction models were developed on the basis of three different choices of independent variables, whereas the incident detection algorithms used different decision functions. The results show that a good prediction model can improve the performance of an incident detection algorithm only when the decision function of the algorithm is appropriately chosen.
Intellectual Challenges to Deployability of Advanced Vehicle Control and Safety Systems
Authors: Shladover Steven E.
Published: April 2007

The U.S. Department of Transportation (DOT) has become increasingly interested in identifying what it can do to facilitate the rapid deployment of advanced vehicle control and safety systems (AVCSSs) under its new Intelligent Vehicle Initiative. The primary topic areas in which the current state of knowledge is inadequate to support the development and evaluation of the effectiveness of AVCSSs are identified. These topics (quantification of driving hazards, quantitative description of traffic behavior, identification of driver responses to stimuli, determination of the influences of AVCSSs on driver behavior, prediction of market response to availability of AVCSSs, and identification of the effects of AVCSSs on traffic flow) represent the kinds of cross-cutting precompetitive research subjects that could provide the principal focus for DOT contributions to facilitating the eventual deployment of AVCSSs. The state of knowledge in these areas needs to be improved substantially before it will be possible to design safe and effective AVCSSs or to evaluate the relative value of different potential AVCSS solutions to transportation problems.
Development of Vision-Based Vehicle Detection and Recognition System for Intelligent Vehicles
Authors: Ran Bin , Liu Henry X.
Published: April 2007

The business plan for the Intelligent Vehicles Initiative (IVI) from the U.S. Department of Transportation contains several candidate services that address collision warning and collision avoidance. Recently, a proactive crash mitigation system that would enhance the crash avoidance and survivability components of IVI has been proposed. An accurate object detection and recognition system is a prerequisite for the proactive crash mitigation system. A vision-based approach to the detection and recognition of vehicles, calculation of their motion parameters, and tracking of multiple vehicles by using a sequence of gray-scale images taken from a moving vehicle is presented. The vision-based system consists of four models: the object detection model, the object recognition model, the object information model, and the object tracking model. Object detection, recognition, and tracking are accomplished by combining the analysis of a single image frame with the analysis of consecutive image frames. In the analysis of the single image frame, the system detects the potential objects by using their shape features and recognizes the objects by using a neural network. Once the objects are recognized, they are tracked in the consecutive image frames by processing only the pertinent areas given by previous frames. The analysis of the single image frame is performed every 10 image frames. The information model will judge whether the objects are hazardous to the host vehicle by using two parameters: time to collision and its time derivative. Experimental results demonstrated a robust system in real-time vehicle recognition, vehicle tracking, and vehicle motion analysis over thousands of image frames.
Development of Hierarchical Methodology for Benefit Evaluation of Vehicle-Highway Automation: Case Study of the Houston Katy Freeway
Authors: Miller Mark A. , Misener James A. , Godbole Datta N. , Deshpande Akash R.
Published: April 2007

A hierarchical methodology used to design and benefit the evaluation of vehicle-highway automation systems at various levels of granularity is described. In this hierarchy, detailed microsimulation and experimental data and performance measures feed into consecutively higher, system-level analyses. Ultimately, top-level estimates of system benefits are provided to transportation decision makers. The method is designed to accommodate studies of autonomous vehicle control concepts such as the safety services under consideration as advanced vehicle control and safety system (AVCSS) intelligent transportation system services, some of which have been discussed as U.S. Department of Transportation Intelligent Vehicle Initiative services; it will also accommodate studies of the fully automated highway systems. The method is illustrated with a multifaceted set of studies of the relationship between the degree of automated vehicle-highway cooperation and system performance improvement on the Houston, Texas, Metropolitan Transit Authority High-Occupancy Vehicle facility on Interstate 10, also known as the Katy Freeway. The primary objective is to predict performance impacts for alternative concepts, which will undergo a major investment study, in a real-world setting. The study initially focused on automated highway systems, but the methodology has since been applied to the adaptive cruise control AVCSS service.
Breaking the Highway Capacity Barrier: Adaptive Cruise Control-Based Concept
Authors: Godbole Datta N. , Kourjanskaia Natalia , Sengupta Raja , Zandonadi Marco
Published: April 2007

A single-lane advanced vehicle-highway concept that can increase driving comfort and highway capacity is proposed. The concept can be implemented in the near future as it uses the adaptive cruise control (ACC) technology on vehicles and the intelligent ramp metering technologies on the roadway. A simulation-based performance evaluation of single-lane ACC systems under different traffic conditions is presented. The results indicate that drivers can fully use ACC systems even in stop-and-go-traffic, thereby reducing driving stress. It is also shown that ACC-equipped vehicles can maintain a desired intervehicle gap of 1 s under different traffic conditions while attenuating traffic disturbances, thereby resulting in a traffic flow of up to 3,000 vehicles per hour per lane with properly designed intelligent ramp metering at entrances to such a highway.
Analysis of International Border Clearance Technologies
Authors: Atalla George
Published: April 2007

Dedicated Short Range Communication (DSRC) technology was implemented at land-border ports to support the International Trade Data System’s (ITDS’s) vision of nonstop paperless border processing. Subsequent evaluation concluded that the implemented DSRC systems inadequately supported the ITDS objectives. Consequently, alternative technologies were assessed that could support multimodal border processing. Alternative technologies considered are divided into two main categories: ( a) short-range systems that include laser, radio frequency, and automated teller machine (ATM) technologies and ( b) wide-area systems that include cellular telephony, radio data network services, and satellite communications. The names of the companies proposing technologies still in development were withheld. The data indicate that several widely used and off-the-shelf technologies, such as Qualcomm, Type II transponders, and ATM systems, are capable of only partially supporting the functional requirements of ITDS border processing. A proposal that combines cellular and radio-frequency technology, which came closest to satisfying the ITDS requirements, is still new and untested. It was found that short-range technology is inadequate for supporting sea and air transportation modes. Wide-area systems are costlier and are incapable of supporting lane discrimination and automatic decision and exit notification at land-border ports without the support of other on-board short-range automatic vehicle identification devices. On the basis of the findings, the solution that combines cellular and radio-frequency technology seems to address most of the ITDS border processing requirements and may merit further consideration.
Selecting a Preventive Maintenance Treatment for Flexible Pavements
Authors: Hicks R. Gary , Moulthrop James S. , Daleiden Jerry
Published: April 2007

Maintenance engineers have been applying treatments to both flexible and rigid pavements ever since there have been these types of pavements. The types and application of various treatments for both corrective and preventive maintenance have been the subject of research studies over a number of years, and many publications have reported these findings. FHWA recently initiated an effort to encourage departments of transportation at all levels to begin, or extend, the practice of preventive maintenance, since there simply is not enough money available to continue the types of maintenance currently employed. Flexible pavement preventive maintenance is specifically addressed, including the types of pavements that are candidates for preventive maintenance, the available treatments, where and when they should be used, their cost-effectiveness, factors to be considered in selecting the appropriate treatment strategy, and a methodology to determine the most effective treatment for a particular distress.
Method To Evaluate Rigid-Pavement Joint Sealant Under Cyclic Shear and Constant Horizontal Deflections
Authors: Al-Qadi Imad L. , Abo-Qudais Saad , Khuri Ramzi E.
Published: April 2007

In recent years, the need for sealants in rigid pavement joints has become debatable, partly because of the unpredictable field performance of joint sealants. This inability to predict sealant performance stems from the fact that there is no laboratory evaluation method that accurately simulates field traffic and environmental loading conditions. A laboratory testing method was developed to predict the performance of rigid-pavement joint sealants. A research team at Virginia Tech designed a fixture that allows the evaluation of joint sealants under cyclic shear and static horizontal deflections. Shear deflection simulates vehicular loading, and horizontal deflection simulates expansion and contraction of concrete slabs due to temperature variation. Concrete specimens were prepared at a typical water-to-cement ratio of 0.45. Two aggregate types were used in the concrete mixes to evaluate the effect of aggregate type on sealant performance. Two commercially available sealants were investigated in the study. Sealant performance was evaluated for different joint widths and joint expansion. Specimens were loaded cyclically to failure; a 20 percent cohesive or adhesive debonding was considered a failure. A limited number of specimens were exposed to freezing and thawing cycles. The study showed quantitatively the effects of joint width, joint expansion, concrete aggregate type, and freezing and thawing cycles on sealant performance. Statistical models were developed to predict the number of loading cycles to failure for each sealant.
Material Characterization of Silicone Sealants
Authors: Lynch Larry N. , Janssen Donald J.
Published: April 2007

Silicone sealants were analyzed using dynamic shear rheometry (DSR) and numerical analysis to determine if a method could be developed that would provide the basis for a performance-based specification. The research used a three-phase approach including DSR analysis of aged and unaged sealants, numerical model development using the DSR data as input, and laboratory tension experiments for model verification. Results of the investigation indicated that the average material properties determined through DSR and laboratory tensile testing appeared to be representative of the “true” material properties for elongations of up to 25 percent. The results were less accurate for 50 percent elongation but still acceptable. The DSR testing could be related to field performance; however, conducting several tests on multiple samples to develop a discrete stress-relaxation spectrum for numerical analysis would not be feasible for most users. Instead, two test temperatures should be selected for DSR testing based upon the maximum and minimum in-use temperature the sealant would be exposed to for a given application.
Fundamental Concepts of Heat-Straightening Repair for Damaged Steel Bridges
Authors: Avent R. Richard , Mukai David
Published: April 2007

Much misinformation has been disseminated about the fundamentals of heat-straightening repairs for damaged steel bridges. Providing the practitioner with an understanding of these fundamentals is the aim. Included are an explanation of why heat straightening works, how to classify damage, keys for successful heat straightening, fundamental heating patterns, how and why to control heating temperature, and the proper use of jacking forces. A practical understanding of heat straightening is provided.
Laboratory Optimization of Asphalt Concrete Intermediate Course Mixes To Improve Flexible Pavement Performance
Authors: Abdulshafi Osama A. , Fitch Michael G. , Kedzierski Bozena , Powers David B.
Published: April 2007

It has long been known that the use of carefully designed asphalt concrete mixes can increase the rutting resistance and structural capacity of flexible pavements. Unfortunately, optimization of asphalt mixes for intermediate pavement courses has been inhibited in the past by the use of wide limits in the aggregate gradation. This has sometimes led to insufficient amounts of top-size and fine aggregate, suboptimal packing density, unnecessarily high asphalt cement contents, and a resultant lack of stone-on-stone contact and mix stability. In addition, accurate laboratory evaluation of intermediate course mixes has been hampered by the use of traditional 10-cm (4-in.) specimen molds, which are too small to yield representative test results for some mixes with 2.5-cm (1-in.) aggregate. This study consisted of laboratory evaluation of 10 asphalt concrete intermediate course trial mixes, with five different dense gradations for two aggregate types: natural gravel (rounded) and crushed limestone (angular). The five gradations (nominal maximum aggregate size, 2.5 cm) were developed following an overall volumetric concept as used in the design of portland cement concretes. Test specimens were prepared with 15-cm (6-in.) molds. Specimens prepared at the determined optimum asphalt cement contents were tested for modulus of resilience, indirect tensile strength, indirect tensile creep, unconfined compressive strength, and resistance to moisture-induced damage. Mixes based on three of the evaluated gradations consistently showed superior performance to traditional mixes. Recommended mix design criteria are provided to assist in optimization of intermediate course mixes.
Using Superpave Performance Tests To Evaluate Asphalt Mixtures
Authors: Anderson R. Michael , Bukowski John R. , Turner Pamela A.
Published: April 2007

The original intent of the Superpave performance tests was for the results to be input into performance models developed during the Strategic Highway Research Program that would output a prediction of various forms of pavement distress as a function of time or traffic. Unfortunately, recent research has indicated that the Superpave performance models, and some of the performance tests, have critical errors that make performance prediction impossible. Still, a substantial amount of testing has been conducted since 1994 to analyze the performance properties of asphalt mixtures. Although these data cannot be used to predict pavement performance as originally intended, the output of the Superpave performance tests can be used to calculate mechanical properties that permit relative determinations of an asphalt mixture’s stiffness and estimations of its ability to withstand permanent deformation. The objective of this study is to provide documentation of performance test results of various asphalt mixtures tested since 1994. This information is a portion of a developing database on mechanical properties of asphalt mixtures tested with the Superpave shear tester. It is intended that these values can provide guidance to the user indicating how a project’s asphalt mixture compares with other mixtures with a performance history. The study also considers the effect of changes in mixture components, sample reheating, and type of Superpave gyratory compactor on the mechanical properties of an asphalt mixture.