bluuebunny/crossref_metadata_2025 huggingface dataset:
Incorporating Crash Risk in Selecting Congestion-Mitigation Strategies: Hampton Roads Area (Virginia) Case Study
Authors: Garber Nicholas J. , Subramanyan Sankar
Published: April 2007

The extensive research under way to forecast traffic volumes from realtime data is expected to result in a significant increase in the use of realtime data for congestion mitigation and management in the next few years. Unfortunately, congestion-mitigation strategies based solely on these forecast volumes will disregard the impact of other traffic variables on crash occurrence. This may result in congestion-mitigation strategies that improve traffic flow but significantly increase crash rates. These other variables, for which real-time data are also available in traffic management centers, include speed and occupancy. However, real-time data have not been widely used in research to develop mathematical models that relate crash rates with these other traffic variables. The availability of this type of relationship will enable engineers in the field to develop congestion-mitigation strategies based not only on forecast volumes but also on real-time information on traffic variables such as speed and occupancy. A procedure that uses real-time data on traffic flow, speed, and occupancy and the relationship between these variables and crash occurrence could be used to develop congestion-mitigation strategies that incorporate safety. Currently, no such decision-support tool is readily available to the traffic engineer. The feasibility of developing such a methodology in which real-time data could be used to develop congestion-mitigation strategies that also consider crash risk was investigated. Models showing the relationship between flow and occupancy and between number of crashes and occupancy were developed for specific sites in the Hampton Roads, Virginia, area. These models were then used to illustrate how diversion strategies that consider crash risk may be developed.
Sensor-Friendly Vehicle and Roadway Cooperative Safety Systems: Benefits Estimation
Authors: Misener James A. , Thorpe Chuck , Ferlis Robert , Hearne Ron , Siegal Mel , Perkowski Joe
Published: April 2007

An analysis was performed to estimate the potential national costs and benefits of cooperative vehicle and roadway measures to enhance the effectiveness of driver assistance systems. These cooperative measures—query-response communication systems, light-emitting-diode brake light messaging, radar cross-section paint-striping modifications, fluorescent paint for lane and other marking applications, passive amplifiers on license plates, spatial tetrahedral arrays of reflectors, and in-vehicle corner cubes—are briefly described, along with assumptions that were made regarding performance. For the example lane departure case, the incremental nationwide effectiveness over an autonomous collision-avoidance system is estimated and monetized. This was generally determined with respect to annual crash-reduction savings, although the technique used allows other mobility benefits to be considered. The marginal benefits of providing each sensor-friendly technology were then calculated and aggregated across the various Intelligent Vehicle Initiative services so that a total marginal benefit was determined for each technology. Complementing this, a method has been established to estimate the magnitude of at- and near-intersection lead-vehicle-not-moving crashes for these technologies. Together, these methods illustrate national benefits across all crash types (the three-step process) and a more focused means to estimate benefits for a particular crash type (rear-end collisions at or near intersections)—and provide a composite approach to the problem.
Interstate Highway Crash Injuries During Winter Snow and Nonsnow Events
Authors: Khattak Aemal J. , Knapp Keith K.
Published: April 2007

Many regions across the United States experience a number of winter snow events every year, during which a multitude of vehicular crashes occur. The authors formally compare crashes and occupant injuries reported on Interstate highways in Iowa during winter snow event periods with those reported during equivalent winter nonsnow event periods. The comparison is fairly comprehensive because it includes detailed crash, weather, and roadway geometry information on seven different sections of the Iowa Interstate highway system. Further, the analysis utilizes traffic count data specific to snow event and comparable nonsnow event periods. The comparison was facilitated by using a geographic information system that merged data from a variety of sources, resulting in the creation of a unique data set with significant spatial and temporal coverage. After explicitly controlling for seasonal, monthly, weekly, hourly, and locational variations in crash occurrence, significant increase was observed when winter snow event injury and noninjury crash rates (crashes per million vehicle kilometers) were compared with equivalent winter nonsnow event injury and noninjury crash rates. The data were then analyzed for injury occurrence. Results of a logit model indicated that crash injury occurrence on Interstate highways in Iowa depended on traffic, road geometry, and number of vehicles involved in a crash. Another finding from the logit model was that crashes during snow events were less injurious compared with equivalent nonsnow event crashes. Snow event–specific crash data were then analyzed to study the effects of snow event elements (e.g., snowfall intensity) on injury occurrence in vehicular crashes.
Bayesian Identification of High-Risk Intersections for Older Drivers via Gibbs Sampling
Authors: Davis Gary A. , Yang Shimin
Published: April 2007

Hierarchical Bayes methods are combined with an induced exposure model in order to identify intersections where the crash risk for a given driver subgroup is relatively higher than that for some other group. The necessary computations are carried out using Gibbs sampling, producing point and interval estimates of relative crash risk for the specified driver group at each site in a sample. The method is applied to data from 102 signalized intersections, and 10 were identified as showing high risk for older drivers. Left-turn crashes tended to predominate at these 10, whereas rear-end crashes were most common at geographically similar intersections not identified as showing high risk to older drivers.
Automated Accident Detection System
Authors: Harlow Charles , Wang Yu
Published: April 2007

The development of a system for automatically detecting and reporting traffic accidents at intersections was considered. A system with these properties would be beneficial in determining the cause of accidents and could also be useful in determining the features of the intersection that have an impact on safety. A complete system would automatically detect and record traffic conditions associated with accidents such as time of the accident, video of the accident, and the traffic light signal controller parameters. The basic research required to develop the system is considered. This involves developing methods for processing acoustic signals and recognizing accident events from the background traffic events. A database of vehicle crash sounds, car braking sounds, construction sounds, and traffic sounds was created. The mel-frequency cepstral coefficients were computed as a feature vector for input to the classification system. A neural network was used to classify these features into categories of crash and noncrash events. The classification testing results achieved 99 percent accuracy.
Evaluation of Inexpensive Global Positioning System Units to Improve Crash Location Data
Authors: Graettinger Andrew J. , Rushing Timothy W. , McFadden John
Published: April 2007

The state of Alabama stores and manages detailed information about vehicle crashes including their approximate locations. Currently, crash locations are estimated and hand recorded by highway patrol officers at the scene of a crash. These locations are typically placed at identifiable points along the roadway, such as mileposts and intersections. The resulting resolution can place vehicle crashes caused by the same roadway variable as far apart as 2 km, making accurate identification of roadway safety hazards difficult. The research project was initiated through the University Transportation Center for Alabama to improve vehicle crash analysis through accurate and inexpensive collection and display of crash locations. The research employed Global Positioning System (GPS) and Geographic Information System (GIS) technologies. GPS units ranging in price from $130 to $3,400 were evaluated on the basis of cost, accuracy, usability, additional equipment needed, and time required to collect a location. From this analysis two GPS units were selected: ( a) a handheld unit, the Garmin GPS 12 Map, and ( b) a computer-based unit, the Rand McNally StreetFinder Deluxe. With the recent removal of selective availability, the research has shown that inexpensive GPS units tested are capable of locating a vehicle crash within an 8-m radius. In addition, both an off-the-shelf GIS and accurate basemaps were employed to display the new GPS crash data. By analyzing GPS locations in a GIS, “hot spots” where multiple crashes occurred were identified through buffering operations. An analysis of actual crash location data showed that GPS data provided more information about a crash than conventional methods, specifically at interchanges and along roadway segments.
Road Financing and Management in the Baltic States
Authors: Rodzik Ewa , Queiroz Cesar
Published: April 2007

Until the early 1990s, the Baltic states, namely, Estonia, Latvia, and Lithuania, were constituents of the former Soviet Union. When the Baltic states achieved independence, they faced challenges in finding ways to develop and maintain their neglected road networks. The new republics organized individual road administrations according to their specific needs and governmental frameworks. They chose different means of collecting and distributing the funds needed for their national road networks. Before independence, all road construction and maintenance were done by force account. Since independence, the road administrative structures and financing arrangements have undergone considerable change. A common concern in the three Baltic states is that the current levels of funding for roads are lower than those needed to maintain their national road networks. If adequate funding is not available, it is likely that there will be increased backlogs of periodic maintenance, resulting in a greater need for reconstruction later. The present system of management and financing for roads in each of the three governments is discussed. A brief comparative analysis of the markedly different approaches to management and financing of the road networks in each of the three Baltic states is also presented. The sources of the information include publications and interviews with road administrations during missions to the Baltic states.
Finances of Commercialized Urban Road Network Subject to Congestion Pricing
Authors: Roth Gabriel , Villoria Olegario G.
Published: April 2007

Estimates of congestion costs in the Metropolitan Manila, Philippines, area and of the additional charges necessary to reduce traffic volumes to levels at which the congestion charges (paid by vehicle users) equal congestion costs (which their vehicles impose on the rest of the traffic) are presented. Calculations indicate that, on the basis of reported values of time for different vehicle classes and elasticities of the demand for road use assumed to be in the range of -0.1 to -1.0, a congestion charge in the range of 6 to 14 Philippine pesos (Php) per passenger car unit per km would be appropriate. Calculations also indicate that such a charge would likely increase traffic speeds by 44 to 101 percent. Traffic volumes would fall by 11 to 24 percent, with traffic with low time values falling more than traffic with high time values. Total revenues of 10.2 billion to 23.1 billion Php in congestion charges and a further 2.4 billion Php in parking charges could be raised each year, thus offering gross revenues of 12.6 billion to 25.5 billion Php/year to a Manila commercial highway organization (MaCHO). Net revenues to MaCHO could range from 5.6 billion to 14.3 billion Php/year.
Impact of Variable Pricing on Temporal Distribution of Travel Demand
Authors: Cain Alasdair , Burris Mark W. , Pendyala Ram M.
Published: April 2007

Despite the potential of congestion pricing to ease the nation’s ever-increasing congestion problems, there is little quantitative evidence of its ability to spread peak travel demand more efficiently over the course of the day. The objective of the present work is to assess the impact of variable pricing on the temporal distribution of demand to investigate further the role of variable pricing as a travel demand management tool. The Variable Pricing Program of Lee County, Florida, was used as the data source for the study. Because of the limited congestion experienced at the program location, the effects of travel cost changes on the temporal distribution of demand could be isolated. It was found that program implementation had a minimal impact on the overall distribution of demand. Demand for peak-period travel remained relatively unaltered, and active peak spreading was not observed. At the more disaggregate level, however, the impact of the program was more apparent, with significant temporal shifts in the proportion of demand within individual half-hour time segments. Further analysis revealed a price elasticity relationship that was consistent with that in the existing literature. A relationship was also observed between the extent of preprogram peak spreading and the subsequent percent reduction in peak-period travel demand after program implementation. This finding suggests the potential to predict the active peak spreading that may result from congestion pricing. The fact that substantial temporal shifts in travel demand were observed in response to a discount of only 25 cents highlights the potential of variable pricing as a travel demand management tool.
Regional Strategies for the Sustainable Intermodal Transportation Enterprise: Five Years of Research
Authors: Sussman Joseph M. , Conklin Christopher
Published: April 2007

For the past 5 years the Regional Strategies for the Sustainable Inter-modal Transportation Enterprise (ReS/SITE) project has worked on the development of new regional transportation planning frameworks that recognize the realities of modern-day regional economic development. The project began with the identification of a number of weaknesses in conventional regional transportation planning and set about the development of an expanded framework that would remedy these shortcomings (including intermodalism, technology scanning, freight, private-sector involvement, economic integration, national information infrastructure-telecommunications-transportation relationships, master plan perspective, and human resource development). A new framework emerged, based on the idea of scenarios, as advanced by Royal Dutch Shell in the 1970s, and on an expanded notion of regional architectures reflecting the new organizational interactions required to plan and manage transportation systems at a regional scale. This framework has been applied in case studies in Houston, Texas, and Mexico City, Mexico, over the past several years, and the methodology has been greatly refined as a result of those applications. How the new ReS/SITE structure addresses the shortcomings in the planning process is indicated, and some further steps in framework expansion and refinement are suggested.
Assessing Economic Benefits from Implementation of New Pavement Construction Methods
Authors: Gillen David , Harvey John , Cooper Douglas , Hung David
Published: April 2007

The benefits of pavement research are often presented in measures of interest to pavement engineers and managers. These pavement measures must be rationally converted to monetary measures so that the public and managers without pavement training can evaluate the return on their investment in pavement research. An evaluation of the economic costs and benefits of implementation of three recommendations for changes in flexible pavement design and construction is presented. The analysis was performed by using a full-cost model developed for transportation projects that includes direct agency costs, user costs, and safety costs. The analysis procedure was applied to a generic rehabilitation project of the California Department of Transportation (Caltrans), the results of which were extrapolated to the state network. The results indicate potential savings of direct agency costs of hundreds of millions of dollars. The results were also applied to a set of rural Caltrans highway rehabilitation projects.
Methodology to Determine Load- and Non-Load-Related Shares of Highway Pavement Rehabilitation Expenditures
Authors: Li Zongzhi , Sinha Kumares C. , McCarthy Patrick S.
Published: April 2007

A marginal cost method for quantitative assessment of the load- and non-load-related shares of pavement rehabilitation expenditures is described. A set of ordinary least-squares models was formulated by an aggregate approach. The study revealed that the shares of pavement rehabilitation expenditures attributable to load factors depend on pavement type, year of study, and other variables. The load- and non-load-related fractions of rehabilitation expenditures used to repair pavement damage were found to be 28 and 72 percent, respectively, for flexible pavements, 78 and 22 percent, respectively, for jointed concrete pavements, and 38 and 62 percent, respectively, for composite pavements. It is expected that the results of the study will facilitate the apportionment of pavement rehabilitation expenditures for highway cost allocation in a fair and equitable manner.
Productivity Benefits and Cost Efficiencies from Intelligent Transportation System Applications to Public Transit: Evaluation of Advanced Vehicle Location
Authors: Gillen David , Chang Elva , Johnson Doug
Published: April 2007

Total factor productivity (TFP) techniques were used to develop measures of productivity performance for public transit systems of varying size and location. This baseline is used to examine the potential contribution of alternative advanced vehicle location (AVL) applications. TFP aggregates outputs on the basis of their revenue contribution and inputs on the basis of their relative importance to total costs to calculate the overall transit firm productivity as a function of these quantities. This approach provides a measure of efficiency contribution and identifies the instruments that can be used to achieve these gains. The results from the study are insightful. AVL was found to be an important factor in both system performance and cost savings. The introduction of AVL had a positive and significant impact on transit firm productivity. Improvements in productivity and better service information can be obtained through use of AVL. In the bus fleet regression, AVL has a negative coefficient, indicating that the use of AVL by a transit firm will result in fewer buses used given the number of vehicle miles and number of passenger trips. Similarly, cost per vehicle mile was found to be lower when the transit firm used AVL. In addition to these cost savings, research indicates that given fleet size and usage AVL will reduce the annual maintenance hours for a firm.
Empirical Examination of Relationship Between Firm Location and Transportation Facilities
Authors: Kawamura Kazuya
Published: April 2007

The locations and profiles of firms in the six-county Chicago, Illinois, region were used to compare the businesses’ proximities to freeway ramps and transit stations for two time periods: 1981 and 1999. A series of regression models was constructed to assess whether the location patterns with respect to transportation facilities have changed over the last two decades. The data suggest that, controlling for exogenous factors, businesses have moved closer to freeway ramps in the last two decades. Meanwhile, the distance to transit stations has not changed except in the city of Chicago, where it has decreased. These findings suggest shifts in location choice behaviors in the urban core and the suburbs. Specifically, firms in the urban core areas are valuing access to rail stations to a greater degree, whereas those in the suburbs are placing more importance on proximity to freeway ramps. The concentration of businesses near expressway ramps in the inner and middle suburbs suggests the emergence of a pattern in those areas that corresponds to a polycentric development, with freeway ramps as the focal points. Finally, the findings indicate a shift, not a decrease, in the importance of transportation access for business location choice.
Rural Inland Waterways Economic Impact Kit: A Synopsis
Authors: Hamilton Gregory L.
Published: April 2007

The results of a project whose primary objective was the development of a PC-based kit that gives users the ability to perform an assessment of the economic impacts of existing rural inland waterway ports and terminals are reported. The kit’s design follows a step-by-step procedure that focuses on the economic impacts of cargo flows, port users’ industries, and capital expenditures through the port or terminal linkages to regional industrial structures and transportation systems. The kit is interactive, guiding users through the impact analysis, and allows the users to input data and modify the model’s data while maintaining a consistent approach throughout the analysis. The major elements of the kit are summarized, and in particular the derivation of the kit’s input-output model and major issues that had to be resolved in constructing the kit are focused on.
Applying Governmental Accounting Standards Board Statement 34: Lessons from the Field
Authors: Kadlec Anthony J. , McNeil Sue
Published: April 2007

In June 1999 the Governmental Accounting Standards Board (GASB) issued a reporting requirement that state and local governments show the value of the infrastructure assets that they own. The use of these guidelines is very controversial. However, most state statutes mandate that state and local agencies follow the guidelines. It is shown that the application of GASB Statement 34 is consistent with principles of good asset management. Data and procedures from the pavement management system for the city of Hopkins, Minnesota, are used to illustrate the application of the GASB requirements.
Stakeholder Requirements for Traffic Signal Preemption and Priority in Washington, D.C., Region
Authors: Gifford Jonathan , Pelletiere Danilo , Collura John
Published: April 2007

The needs, issues, and concerns are identified of local elected officials and transportation and emergency personnel from the Washington, D.C., area about signal priority and preemption systems. These needs, issues, and concerns are used to generate a set of system objectives and general requirements that state and local decision makers might use in evaluating these systems in the future. As reported, although emergency and transit agency personnel are actively interested in this technology, they and the other stakeholders have significant questions and reservations to be considered in the adoption and deployment of preemption and priority systems.
Method for Real-Time Recognition of Vehicle Platoons
Authors: Gaur Anshoo , Mirchandani Pitu
Published: April 2007

An approach for the real-time recognition of vehicle platoons based on the time epochs of vehicles passing over a point (detector) on a link is introduced. Since platoons on a link depend on its traffic volume and the distribution of the vehicle headways, the algorithm first computes second-by-second vehicle density (vehicles per second) for each network link. To identify platoon beginnings and endings, this link density is multiplied by two fixed factors, one greater than 1 and the other less than 1, to obtain upper link density and lower link density, respectively; these are subsequently utilized in the platoon-recognition process. Using detector data from microsimulations of traffic scenarios, the platoon-recognition method is evaluated with respect to the following measures of effectiveness: percentage of vehicles captured in platoons, platoon size distribution, platoon densities, number of platoons versus percentage of free time (defined as the time between platoons), model robustness, and computational time.
Real-Time Offset Transitioning Algorithm for Coordinating Traffic Signals
Authors: Abbas Montasir , Bullock Darcy , Head Larry
Published: April 2007

A traffic signal offset transitioning algorithm is introduced that can be viewed as an integrated optimization approach designed to work with traditional coordinated-actuated systems. The proposed approach assumes a fixed cycle length (selected by either time of day or some traffic-responsive technique). The splits are determined by each local controller subject to maximum and minimum constraints traditionally imposed by coordinated-actuated signal systems. End-of-green offsets at each intersection are continually adjusted by the proposed algorithm with the objective of providing smooth progression of a platoon through an intersection using the volume and occupancy profile of advance detectors. The algorithm was implemented in a hardware-in-the-loop simulation and evaluated with a set of National Transportation Communications for Intelligent Transportation Systems Protocol (NTCIP) National Electrical Manufacturers Association controllers. The offsets were manipulated with NTCIP messages. The unique aspect of this algorithm is the cycle-based procedure used to tabulate volume and occupancy profiles, which can then be used to adjust the offsets in a traditional coordinated-actuated signal system. This automatic tuning process is analogous to an engineer or technician standing beside the cabinet and tuning the offset so that the coordinated phase turns green at the appropriate time to facilitate smooth progression of the upstream platoon. Because only the offsets are tuned, it is unlikely that this algorithm will be able to achieve the global optimum parameters or rapid adaptation possible with model-based approaches; nevertheless, this algorithm has the advantage of working within the framework of traditional coordinated-actuated signal systems that are familiar to system operators.
Assessment of Stochastic Signal Optimization Method Using Microsimulation
Authors: Park Byungkyu “Brian” , Rouphail Nagui M. , Sacks Jerome
Published: April 2007

A stochastic signal optimization method based on a genetic algorithm (GA-SOM) that interfaces with the microscopic simulation program CORSIM is assessed. A network in Chicago consisting of nine signalized intersections is used as an evaluation test bed. Taking CORSIM as the best representation of reality, the performance of the GA-SOM plan sets a ceiling on how good any (fixed) signal plan can be. An important aspect of this approach is its accommodations of variability. Also discussed is the robustness of an optimal plan under changes in demand. This benchmark is used to assess the best signal plan generated by TRANSYT-7F (T7F), Version 8.1, from among 12 reasonable strategies. The performance of the best T7F plan falls short of the benchmark on several counts, reflecting the need to account for variability in the highly stochastic system of traffic operations, which is not possible under the deterministic conditions intrinsic to T7F. As a sidelight, the performance of the GA-SOM plan within T7F is also computed and it is found to perform nearly as well as the optimum T7F plan.
Optimal Coordinated Ramp Metering with Advanced Motorway Optimal Control
Authors: Kotsialos Apostolos , Papageorgiou Markos , Middelham Frans
Published: April 2007

A generic approach to the problem of optimal coordinated ramp metering control in large-scale motorway networks is described that is implemented in the software tool Advanced Motorway Optimal Control. In this approach, the traffic flow process is modeled by use of a secondorder macroscopic traffic flow model. The overall problem of coordinated ramp metering is formulated as a constrained discrete-time nonlinear optimal control problem, and a feasible-direction nonlinear optimization algorithm is employed for its numerical solution. The control strategy’s efficiency is demonstrated through its application to the 32-km long Amsterdam ring road. A number of different scenarios with regard to the number of controlled ramps and the available storage space are discussed in some detail. The results of the presented approach are very promising and demonstrate the high efficiency and general applicability of the optimal control methodology for motorway traffic control problems.
Modifying Signal Timing During Inclement Weather
Authors: Perrin H. , Martin Peter T. , Hansen Blake G.
Published: April 2007

Most individuals living in cold climates realize that on snowy days their commute will take longer. Although traffic volumes are often lower, the combination of reduced speeds and capacity causes severe congestion, particularly on signalized urban networks. Signal coordination that reduces traffic congestion in typical clear conditions results in an uncoordinated and suboptimal timing plan. Traffic parameters for developing signal timings during inclement weather conditions are examined. With the completion of the Utah Department of Transportation (UDOT) advanced transportation management system, there is an opportunity to change signal timing plans by communicating with each controller from the Transportation Operations Center. This operation makes feasible a library of special signal timing plans, with one allocated for inclement weather. Traffic flow data were collected over a range of seven inclement weather severity conditions at two intersections for the 1999–2000 winter season. The data indicate that the largest decrease in vehicle performance occurs when snow and slush begin to accumulate on the road surface. Saturation flows decrease by 20 percent, speeds decrease by 30 percent, and start-up lost times increase by 23 percent. UDOT is now developing and implementing modified inclement weather coordinated signal timing plans for the major signalized corridors in the Salt Lake Valley. The determination of when to implement an inclement weather signal timing plan is based on four general criteria: storm severity, projected duration, area of influence, and immediately projected running speeds. With these considerations, traffic engineers can determine whether to implement an inclement weather signal timing plan.
Transition Strategies to Exit Preemption Control: State-of-the-Practice Assessment
Authors: Obenberger Jon , Collura John
Published: April 2007

Preempting the normal control of a traffic signal has the potential to affect the safety and efficiency of the vehicle requesting priority and the generalpurpose traffic at the intersection. These impacts may also influence traffic flow at other intersections along a roadway or within the corridor. A state-of-the-practice assessment is provided of different transition strategies used to exit a preemption control plan and return to the coordinated operation of a signal timing plan. The reallocation of green time that results from preempting a traffic signal has the potential to affect the flow of traffic negatively. A methodology that integrates the operation of a traffic signal controller with a microscopic traffic simulation model will accurately replicate the stochastic characteristics of travel and quantify the impacts of preemption control. The time required to exit a preemption control plan will vary on the basis of the exit transition strategy selected, when this plan terminates, and where the normal signal timing plan would have been if it had not been preempted. The preemption control exit transition strategies available to practitioners are typically restricted to the options supported by different types of traffic controllers or firmware products. The five most commonly available exit transition strategies are reviewed, and additional research needed to advance the state of the practice and the state of the art in using preemption control exit transition strategies is also identified.
Online Turning Proportion Estimation in Real-Time Traffic-Adaptive Signal Control
Authors: Mirchandani Pitu B. , Nobe Steven A. , Wu Wenji W.
Published: April 2007

An online method for traffic-adaptive turning proportion estimation for intersections based on a least-squares minimization approach is presented. It assumes that entering-vehicle lane counts and exiting-vehicle counts during every traffic signal phase and in each direction of an intersection are available. Estimations based on field data in the last three cycles (approximately 5 min) are compared with actual values. This method of turning proportion estimation was also implemented within RHODES, a real-time traffic-adaptive signal control system developed in the Advanced Transportation and Logistics: Algorithm and Systems Research Center at the University of Arizona. The resulting system was evaluated in a laboratory using CORSIM, a microscopic traffic simulation computer package. Performance of RHODES improves when the online traffic-adaptive turning proportions are used instead of constant turning proportions.
Texas Driver Understanding of Abbreviations for Changeable Message Signs
Authors: Durkop Brooke R. , Dudek Conrad L.
Published: April 2007

Research was conducted as part of an ongoing project for the Texas Department of Transportation to evaluate the use of changeable message signs (CMSs) in Texas. The objective was to determine motorist understanding of abbreviations for use on CMSs. A human factors study was conducted in six locations in Texas. Participants were given a list of abbreviations and were asked to interpret the full words or phrases. The results identified 24 abbreviations that were understood at an acceptable level for use on CMSs in Texas; acceptability was based on a criterion of 85 percent or more of the participants’ correctly interpreting the word or phrase. Differences in study location comprehension levels were also examined. Twelve abbreviations were recommended for use only at particular locations on the basis of the varying comprehension levels among the six study locations. Abbreviations that were understood by less than 85 percent of the participants were not recommended for use in Texas.
Freeway Performance Measurement System: Mining Loop Detector Data
Authors: Chen Chao , Petty Karl , Skabardonis Alexander , Varaiya Pravin , Jia Zhanfeng
Published: April 2007

Performance Measurement System (PeMS) is a freeway performance measurement system for all of California. It processes 2 GB/day of 30-s loop detector data in real time to produce useful information. At any time managers can have a uniform, comprehensive assessment of freeway performance. Traffic engineers can base their operational decisions on knowledge of the current status of the freeway network. Planners can determine whether congestion bottlenecks can be alleviated by improving operations or by minor capital improvements. Travelers can obtain the current shortest route and travel time estimates. Researchers can validate their theory and calibrate simulation models. PeMS, which has been in stable operation for 18 months, is a low-cost system. It uses the California Department of Transportation (Caltrans) network for data acquisition and is easy to deploy and maintain. It takes under 6 weeks to bring a Caltrans district online, and functionality can be added incrementally. PeMS applications are accessed over the World Wide Web; custom applications can work directly with the PeMS database. Built as a prototype, PeMS can be transitioned into a 7 × 24 production system. The PeMS architecture and use are described.
Breakdown-Related Capacity for Freeway with Ramp Metering
Authors: Persaud Bhagwant , Yagar Sam , Tsui David , Look Horace
Published: April 2007

Research was conducted to better understand the breakdown phenomenon and look for ways of strategically increasing capacity and travel speed by reducing breakdowns on a section of freeway in Mississauga, Ontario, that is subject to ramp metering. The major task was to quantify the probability of breakdown as an increasing function of volume at the critical location. Data from 71 peak periods during which breakdown occurred at the critical merge were used to estimate the function, which was then used in a computer simulation of fixed- and variable-rate metering to demonstrate the potential benefits of using the probability-of-breakdown concept as a basis for ramp metering. The results indicate, for example, that variable-rate metering that complements a constant merge flow limit of 2,320 veh/h per lane could increase peak-hour throughput from about 6,460 to 6,600 veh/h at this location. They also indicate that 2,500 veh/h might be allowed, provided stringent metering for quick recovery to free flow is feasible.
TRICEPS-CARTESIUS: Advanced Transportation Management System Test Bed for Evaluation of Interjurisdictional Traffic Management Strategies
Authors: Logi Filippo , Rindt Craig R. , McNally Michael G. , Ritchie Stephen G.
Published: April 2007

The initial testing and evaluation of one of the key components of the Test-bed Real-Time Integrated Control and Evaluation Prototype System (TRICEPS) are described. TRICEPS is a software platform that facilitates the implementation and evaluation of a wide range of algorithms for traffic control and advanced transportation management systems. TRICEPS supports research activities by providing consistent interfaces for transportation management modules to both simulated and real-world environments. One of the key components of the TRICEPS platform is a distributed architecture for real-time decision support to transportation management center operators that provides a set of core transportation management applications for multijurisdictional traffic control and incident management on freeway and arterial networks. The architecture hosts algorithms for the estimation of current traffic conditions, the analysis of incident characteristics, and the formulation of multiple-decision-maker traffic control plans using advanced methodologies for cooperation and conflict resolution. Although the process of evaluation of such methodologies using the TRICEPS platform is aimed at demonstrating the effectiveness of the cooperative approach, it also provides a demonstration of platform functionality for range of related applications.
Comparative Analysis of Operational Algorithms for Coordinated Ramp Metering
Authors: Kwon Eil , Nanduri Sreemannarayan , Lau Rich , Aswegan James
Published: April 2007

The performance of three different types of traffic-responsive, coordinated ramp metering strategies is analyzed using simulation. The selected metering approaches include the incremental group coordination method being implemented in Denver, Colorado; the fuzzy logic–based, implicit coordination approach from Seattle, Washington; and the bottleneck-based, sectionwide explicit coordination strategy being operated in Minnesota. The macroscopic simulation analysis using a 16-mi (25.7-km) freeway section in Minneapolis, Minnesota, indicated that the incremental coordination approach adopting a queue-override policy resulted in consistently less restrictive metering than did the other two algorithms. Further, the Minnesota system, which does not employ a ramp queue management policy, produced more evenly distributed traffic patterns on the mainline, whereas the fuzzy metering algorithm showed more flexibility in dealing with the atypical demand pattern than did the other metering approaches.
Monitoring Urban Freeway Incidents by Wireless Communications
Authors: Mussa Renatus N. , Upchurch Jonathan E.
Published: April 2007

The efficacy of the driver-initiated incident detection system was assessed by modeling the use of new communications technologies to mitigate problems that beset current cellular call-in programs, problems such as insufficient information on incident location, false reporting, and duplicate calls. An analytical model supported by field data for several important variables was used to determine the system performance measures, that is, the detection rate, mean time to detect, and false alarm rate. The results indicate that with the implementation of new technologies that lead to the automatic geolocation of the driver initiating an incident call, the driver-initiated detection system is effective. The system achieved good detection rates and faster detection times across all simulated incidents occurring under variable traffic flow rates that ranged from light traffic to congested traffic. For instance, even when the proportion of drivers with cellular phones was 1 out of 10, with only 10 percent of them willing to use their phones to report the incidents, close to 80 percent of the incidents were detected within 2 min. This result is consistent with the results of the field studies and shows that even better detection performance can be achieved if current levels of cellular phone ownership in the United States are considered and if drivers’ reporting propensity is raised. It is noteworthy that the Cellular Telecommunications Industry Association reported that there was one cellular phone user per two licensed drivers in the United States at the end of 1999.
Improving Road Quality with Focused Daily Road Maintenance
Authors: Brown Mark , Provencher Yves
Published: April 2007

Growing transportation costs led member companies of the Forest Engineering Research Institute of Canada (FERIC) to request assistance in improving the management of their road systems and thereby lowering road maintenance costs. In response, FERIC developed the Opti-Grade tool, a modified approach to grading that met their needs. It involves focusing road maintenance on the road segments that most need grading, thereby making the most efficient use of graders, lowering grading costs, and improving the performance of the roads, because they are in better condition to deal with traffic and environmental abuse. In addition to the roughness data used for grading schedules, Opti-Grade provides information about average vehicle travel speed on each kilometer of the road. This information can help road managers identify sections of the road that are restricting traffic for reasons such as poor road geometry, high dust levels, poor lines of sight, or high traffic levels. FERIC’s Opti-Grade is an effective management tool for routine road maintenance, and work is being done to make it equally effective for managing road rehabilitation.
Service Life of Durable Pavement Markings
Authors: Migletz James , Graham Jerry L. , Harwood Douglas W. , Bauer Karin M.
Published: April 2007

The service life of durable pavement markings was evaluated over a period of nearly 4 years. The evaluation included 85 study sites in 19 states at which a total of 362 longitudinal pavement marking lines (edgelines, centerlines, and lane lines) were installed. Marking materials included epoxy, flat and profiled polyester, flat and profiled poly(methyl methacrylate), flat and profiled thermoplastic, and profiled preformed tape; glass beads; and standard and snow-plowable raised retroreflective pavement markers. One site with conventional paint markings and three sites with waterborne paint markings were included for comparison. The service life of marking materials and roadway types was modeled as a function of time and cumulative traffic passages. Regression modeling identified large variations in the shape of the relationship for identical materials and types of lines between different sites within a given state and required that modeling be done separately for each pavement marking line at each study site. Variations in service life can be attributed to roadway type, region of the country where the markings were installed (e.g., weather conditions, manufacturers of marking materials and glass beads, and individual state highway agencies), marking specifications, contractors installing the markings, quality control at the time of installation, and winter maintenance snow removal policies.
To Seal or Not to Seal? A Field Experiment to Resolve an Age-Old Dilemma
Authors: Hawkins Bryan K. , loannides Anastasios M. , Minkarah Issam A.
Published: April 2007

Construction and evaluation to date of a joint sealant project in the Wet-Freeze climatic zone near Athens, Ohio, are described. Fifteen different combinations of materials and joint configurations have been used. The new pavement consists of a 250-mm (10-in.) portland cement concrete slab, placed over a 100-mm (4-in.) free-draining base layer, constructed over a 150-mm (6-in.) crushed aggregate subbase, resting over the predominantly silty clay local subgrade. The highway has a 20-year design period and a design traffic level of 11 million single-axle loads. The eastbound lanes were constructed first and have been open to traffic since the spring of 1998, and the westbound lanes have been serving traffic only since the spring of 1999. Evaluations to date indicate that with one exception, preformed compression seals have performed significantly better than liquid sealants. Unsealed sections also are performing very well, exhibiting no visible signs of distress at the joints or in the pavement slabs at this time. In contrast, after only 1 year of service, silicone and hot-pour sealants in the eastbound lanes are in fair to poor condition. The worst sections are those with narrow [3-mm (1/8-in.)] joints. Oversight and inspection provided were ineffective in averting the use of equipment and procedures that were obviously inadequate. The most significant shortcomings appear to have been the omission of sandblasting during placement and inadequate sealant recess.
Highway Bridge Inspection: State-of-the-Practice Survey
Authors: Rolander D. D. , Phares B. M. , Graybeal B. A. , Moore M. E. , Washer G. A.
Published: April 2007

The congressionally mandated National Bridge Inspection Program requires states to inspect periodically all highway bridges on public roads, among other activities; visual inspection (VI) is the primary tool used to perform these inspections. A survey was conducted to help determine current policies and practices that may affect the accuracy and reliability of VI. The survey had three main objectives: to compile a “state of the practice” for bridge inspection, particularly as it pertains to VI; to gather information about bridge inspection management to study how inspection management may influence the reliability of inspections; and to gather data about the current use of nondestructive evaluation technologies and to identify current and future research needs. State departments of transportation, local departments of transportation, and select bridge inspection contractors participated in the survey. Conclusions drawn from this study indicate that the use of nondestructive evaluation has increased since 1993 and that the use of American Society of Nondestructive Testing Level III–certified personnel is increasing. VI was cited as the most frequently used nondestructive evaluation technique; however, vision testing for inspectors is almost nonexistent. Typically, professional engineers were not on site for inspections. State departments of transportation indicated a large demand for future research into the nondestructive evaluation of prestressed concrete superstructures and concrete decks.