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SWUTC Research Project Description

Evaluating Safety Performance and Developing Guidelines for the Use of Right Turn on Red (RTOR)

University:  Texas Southern Univesity

Principal Investigator:
Yi Qi
Center for Transportation Training and Research
(713) 313-6809

Project Monitor:
Daniel F. Lynch
Traffic Engineers, Inc.
8323 SW Freeway, Suite 200
Houston, TX 77074-1609
(713) 270-8145

Funding Source:  State of Texas General Revenue Funds

Total Project Cost: $50,000

Project Number:  161242

Date Started: 5/1/12

Estimated Completion Date:  8/31/12

Project Summary

Project Abstract:
Most studies on RTOR were conducted from the 1970s to the 1990s, right after RTOR operation was widely used in the United States. These studies proved that RTOR is a safe principle. RTOR has been a standard practice and has been accepted enthusiastically by a majority of drivers. However, because of the growth of traffic volume and the emerging of new design alternatives, e.g., dual right-turn lanes, the safety performance of RTOR turned to be uncertain. Moreover, the current versions of the AASHTO Green Book, Highway Safety Manual, and Manual of Uniform Traffic Control Devices do not provide detailed guidelines for the use of RTOR, and it is also hard to find any state standards for the implementation of RTOR, leaving traffic engineers to rely on engineering judgment for their decision making. Therefore, this research aims to investigate the safety performance of RTOR at intersections with new design alternatives. In addition, comprehensive guidelines which incorporate the use of RTOR at intersections with new design alternatives, such as dual right-turn lane, will be provided to traffic engineers for their decision making.

Project Objectives:
The goal of this research is to explore the safety performance of RTOR and to provide recommended guidelines. The results of this project will improve safety and operational efficiency at urban signalized intersections. To achieve this goal, the research will:

  1. Synthesize the safety performance of RTOR based on the existing research,
  2. Summarize best practice and existing guidelines, and
  3. Recommend comprehensive guidelines.

Task Descriptions:
Task 1: Review Literatures on Safety Performance of RTOR.
Basically, there are two major approaches used by previous studies for evaluating the safety performance of RTOR: 1) historical crash data analysis: to compare the right turn related crash rates at intersections before-and-after the application of RTOR, and with-or-without RTOR, and 2) traffic conflict analysis based studies:  to observe and compare the right turn related traffic conflict rates at intersections before-and-after the application of RTOR, and with-or-without RTOR. Traffic conflict is defined as the interaction of two or more road users (e.g., vehicles, pedestrians, and bicycles) in which one or more users take evasive action to avoid a collision. Although crash data are often used to analyze the safety of intersections, the crash data analysis approach may not be feasible in some cases because crashes are very random and rare events that cannot be observed easily during a short time at a limited number of intersections. In the proposed research, both types of studies on RTOR safety performance and their major findings will be thoroughly reviewed.
Subtask 1.1 Historical Crash Data Analysis of RTOR
The subtask aims to conduct a thorough literature review on studies that evaluated the safety performances of RTOR based on historical crash data analysis.  The areas to be reviewed include, but are not limited to

  1. RTOR-related crash rates
  2. RTOR-related crash severity levels
  3. Pedestrian and bicyclists involved crashes

Subtask 1.2 Review Literatures on Traffic Conflict Studies of RTOR
The subtask aims to further evaluate the safety performance of RTOR by reviewing studies that investigated the traffic conflicts related to RTOR. The areas to be reviewed include, but are not limited to

  1. Conflict movements with RTOR
  2. Percentage of traffic conflicts related to RTOR
  3. Types of conflicts and corresponding rates
  4. Percentage of conflicts with pedestrian

Task 2: Review Literatures on Driver Behavior of RTOR
The task aims to review on literatures about driver behavior under RTOR operation. RTOR related driver behaviors, such as proportion of complete stop before turning, sight distance influence, and the human factors (age, gender), have been investigated by previous studies. The results of these studies will be analyzed and summarized for the development of guidelines in Task 5.

Task 3: Synthesize Best Practice and Existing Guidelines on RTOR
This task is to review and synthesize the best practices and existing guidelines on RTOR. Special emphasis will be put on the RTOR implementations at new design alternatives (e.g. dual right-turn lanes). The identified contributing factors to the safety of RTOR will be analyzed and summarized. This result will be served as a basis for the guidelines developed in Task 5.

Task 4: Conduct Field Study to Investigate the Driver Behavior under RTOR Operation at Dual Right-Turn Lanes Intersections
This task is to investigate the driver behavior under RTOR operation at new design alternatives (e.g. dual right-turn lanes). Field study will conducted at selected intersections to characterize gap-acceptance behavioral pattern of individual RTOR drivers turning from dual right-turn lanes.

Task 5: Develop Guidelines for the Use of RTOR
According to the results from Task 1 through 4, guidelines for installation of RTOR at signalized intersections will be developed. The guidelines development will include two types of guidelines: I) mandatory criteria for prohibiting RTOR (RTOR shall be prohibited), which means RTOR must be prohibited at an intersection if one or more of criteria are met, and II) optional criteria for prohibiting RTOR (RTOR may be prohibited), which means RTOR may be prohibited at an intersection if one or more of the criteria are met. The product of this task will be a set of criteria (such as traffic, geometric, and environmental conditions) under which RTOR much be or should be prohibited.

Task 6: Document Research Findings
The purpose of this task is to document all the research findings from Tasks 1 to Task 5. A final report will elaborate the work performed, methods used, and results achieved.

Implementation of Research Outcomes:
This research investigated the safety performance of Right Turn on Red (RTOR) at intersections.  And evaluated new design alternatives, such as dual right-turn lanes and guidelines incorporating the use of RTOR at intersections.

Impacts/Benefits of Implementation:
This research enhances traffic safety by reducing casualties and property damages due to traffic crashes related to RTOR through the comprehensive set of guidelines developed that will support decision-making on the use of RTOR.

Also developed by this research is a new model for gap-acceptance behavior on dual right-turn lanes.  The model is capable of representing the unequal effects of conflicting traffic streams from different cross-street lanes on the gap-acceptance decisions of individual RTOR drivers from dual right-turn lanes.  Enabling the enhancement of modeling of RTOR capacities of dual right-turn lanes in the future.  This model has been published as a ASCE journal paper linked below.

Web Links:
Final Report
ASCE Paper