SWUTC Research Project Description
Title of Project: Development of Pedestrian Safety Based Warrants for Permissive Left-Turn Control
Project Number: 169302
Principal Investigator:
Yi Qi
(713) 313-6809
P.I. Affiliation: Texas Southern University
qiy@tsu.edu
Project Monitor:
Jianming Ma, Ph.D., P.E.
118 East Riverside Drive
Austin, Texas 78704
(512) 923-6456
Project Status: Active
Date Started: 9/1/08
Estimation Completion Date: 8/31/09
Estimated Cost - Current Fiscal: $47,000
Estimated Cost - Total Planned: $47,000
Project Summary:
Project Abstract:
The exiting guidelines on left-turn operations mainly focus on the traffic conditions at the intersections and do not give particular considerations on the pedestrian safety problems. For example, at the intersections with permissive only or protected/permissive left-turn (PPLT) control, pedestrians will move at the permissive phase with the parallel through vehicular movement and the left-turn vehicles have to yield to both opposing vehicles and pedestrians at crosswalk. Under such complicate driving conditions, collision risks rise if left-turn vehicles make misjudgments and fail to yield to the pedestrians. The existing warrants for PPLT control are developed mainly based on the left-turn and the opposing through traffic volumes, while the pedestrian volumes and other pedestrian safety related factors, such as the design features of the crossroads, the sun light directions and the sight distance of the left-turn drivers, have not been explicitly taken into account. Thus, the objective of this research is to develop pedestrian safety based warrants for permissive left-turn control. In this research, the driving-simulation based experiments will be conducted for identifying and assessing the impacts of the factors that contribute to the crashes between left-turn vehicles and pedestrians during the permissive left-turn phase.
Project Objectives:
The objective of this research is to develop pedestrian safety based warrants for permissive left-turn control. The results of this project will improve the safety at the signalized intersections. To achieve these objectives, the research will:
Task Descriptions:
Task 1: Conduct Literature Review
The literature review will focus on the relationship between the left-turn operation and the pedestrian safety at signalized intersections. The areas to be reviewed include:
Emphasis will be put on the factors that influence the pedestrian safety, the existing left-turn operation guidelines (either based on engineering judgment or quantitative analysis).
Task 2: Survey or Interview Traffic Engineers to Identify Influencing Factors
This task is to identify the influencing factors on the pedestrian safety during the permissive left-turn phase by surveying or interviewing the traffic engineers. It will seek the information about their engineering judgments on choosing permissive left-turn control.
Task 3: Design the Test Scenarios for Investigating the Pedestrian Safety Problems Associated With Permissive Left-Turn Control
This task will design the test scenarios for investigating the pedestrian safety problems associated with permissive left-turn control based on the influencing factors indentified through literature review (task 1) and survey (task 2). Various scenarios for testing the impacts of the different influencing factors will be designed using factorial experimental design methods.
Task 4: Develop the Driving Scenarios in a Driving Simulation Environment
Based on the scenarios designed in Task 3, the software applications for the driving simulator, i.e., HyperDrive, will be used to develop these scenarios. The designed scenarios will then be transferred to a driving simulator for conducting the experiments in Task 5.
Task 5: Conduct Driving-Simulation Based Experiments for Assessing the Impacts of the Indentified Influencing Factors
The simulator-based experiments will be conducted to test driver’s driving behaviors and responses to the presence of pedestrians at intersections with different traffic and geometric conditions. During the driving simulations, the safety measures, such as time to collision (TTC) and maximum deceleration rate (DR), will be collected. By comparing these safety measures obtained from difference driving scenarios (the intersections with different pedestrian volume, opposing traffic volume and different geometric conditions, etc), the impacts of the indentified influencing factors on pedestrian safety at the intersections with permissive left-turn control can be assessed.
Task 6: Develop the Pedestrian Safety Based Warrants for Permissive Left-turn Control
According to the experimental results from Task 5, warrants for permissive left-turn control will be developed. These warrants will be developed based on the effects of permissive left-turn control on pedestrian safety. The outcome of this task will be a set of criteria (such as pedestrian volume and left-turn volume) or a decision-making flowchart that indicate whether permissive left-turn control is appropriate or inappropriate for a given intersection.
Task 7: Document Research Results and Findings
The purpose of this task is to produce documentation on all research findings from Tasks 1 to Task 6. A final report which details the work performed, methods used, and results achieved will be developed.
Index Terms:
Left turn lanes, Permissive left turn operations, Intersection elements, Interchanges and intersections, Accident risk forecasting, Risk assessment, Pedestrian movement, Pedestrian safety, Research projects