Robert Brydia

Design policies for sight distance at stop-controlled intersections based on gap acceptance

The current AASHTO policy for sight distance at stop-controlled intersections is based on a model of the acceleration performance of a minor-road vehicle turning left or right onto a major road and the deceleration performance of the following major-road vehicle. This paper develops and quantifies an alternative intersection sight distance model based on gap acceptance. The paper describes field studies that were performed to determine the critical gaps appropriate for use in sight distance design. It is recommended that the sight distance along the major road for a passenger car at a stop-controlled intersection be based on a distance equal to 7.5 s of travel time at the design speed of the major road. Longer sight distances are recommended for minor-road approaches that have sufficient truck volumes to warrant consideration of a truck as the design vehicle. ©

Sight distance for stop-controlled intersections based on gap acceptance

The current AASHTO policy for sight distance at Stop-controlled intersections is based on a model of the acceleration performance of a minor-road vehicle turning left or right onto a major road and the deceleration performance of the following major road vehicle. An alternative intersection sight distance model based on gap acceptance is developed and quantified. Field studies that were performed to determine the critical gaps appropriate for use in sight distance design are described. It is recommended that the sight distance along the major road for a passenger car at a Stop-controlled intersection should be based on a distance equal to 7.5 s of travel time at the design speed of the major road. Longer sight distances are recommended for minor-road approaches that have sufficient truck volumes to warrant consideration of a truck as the design vehicle.

DEVELOPMENT OF INTELLIGENT TRANSPORTATION SYSTEM DATA MANAGEMENT

The intelligent transportation system (ITS) components deployed in U.S. urban areas produce vast amounts of data. These ITS data often are used for real-time operations and then are discarded. Few transportation management centers have any mechanism for sharing the data resources among other transportation groups or agencies within the same jurisdiction. Meanwhile, transportation analysts and researchers often struggle to obtain accurate, reliable data about existing transportation performance and patterns. The development of an ITS data management system (referred to as ITS DataLink) that is used to store, access, analyze, and present data from the TransGuide center in San Antonio, Texas, is presented. Data outputs are both tabular and graphical. No user costs are associated with the system except for an Internet connection.

Development of Active Management Screening Tool

This paper summarizes an FHWA-directed project for the development of an active management screening tool (AMST) for agencies with congestion management process planning tools. The purpose of the AMST is to help those agencies better assess the potential of active management strategies for their region within the congestion management process. Furthermore, the AMST is structured to provide beneficial information and general guidance related to active management strategies in all areas and levels of transportation planning. The tool directly links the transportation planning process with operations by providing regional managers with information about operational strategies that they may find most beneficial to include in their plan for the regional transportation network. The AMST ascertains, at the appropriate screening level, major attributes about candidate corridors that help determine the suitability and appropriateness of an active management strategy. In successive steps the AMST ascertains the best strategy and its companion support that will enhance the facilitys and programs responsiveness to the mobility, safety, and environmental needs of the corridor. Active management strategies included in the tool are high-occupancy vehicle lanes, high-occupancy toll lanes, express toll lanes, nontolled express lanes, exclusive or dedicated truck lanes, exclusive transitways, temporary shoulder use on freeways, speed harmonization, queue warning, dynamic rerouting and traveler information, ramp metering, dynamic merge control, and automated enforcement.

Work Zone Impact Assessment Methods and Applications

Two work zone impact assessment methods were developed and their applicability was illustrated with data from recent construction projects on the I-35 Central Texas corridor. The first method was developed for postevent analyses of the impacts of freeway construction activities, incidents, and special events. The impacts were evaluated in terms of travel times and delay. An interval estimate for maximum queue length was also provided. Travel times and speeds were obtained by Bluetooth address matching. The method has also been used for determining work zone mobility performance measures, verifying the suitability of queue warning systems, and providing feedback for future deployment decisions. Based on more than 3 years’ experience with the analysis of impacts of road construction and maintenance projects as well as some major incidents on the I-35 corridor, the Bluetooth-based postevent closure analysis tool has proved to be very cost-effective. The second method was developed for determining the best closure schedule and start time for planned work zone lane closures. The best closure start time is the one that is expected to create the shortest queue lengths and has the least negative impact on travelers. The required input includes historical traffic volumes at a point upstream of the planned lane closure and estimated work zone capacity. The work zone capacity can vary over the duration of the work zone. The method runs input–output analysis in a dual-loop framework to analyze the impact of all available closure schedule scenarios and selects the best closure start time with the shortest expected queues.

Effectiveness of End-of-Queue Warning Systems and Portable Rumble Strips on Lane Closure Crashes

AbstractThe Texas Department of Transportation (TxDOT) has been deploying work zone intelligent transportation systems (ITS) in an effort to reduce the number of work zone crashes along the Interst...