The National Academies

NCHRP 03-58 [Completed]

Assessing Traffic Control Signal Installations Using Capacity Analysis and Simulation

  Project Data
Funds: $175,000
Research Agency: Texas A&M Research Foundation
Principal Investigator: James A. Bonneson
Effective Date: 8/4/1999
Completion Date: 6/30/2001

The Manual on Uniform Traffic Control Devices (MUTCD) includes warrants that set minimum thresholds for considering installation of a traffic control signal. The MUTCD specifies "satisfaction of a traffic signal warrant or warrants shall not, in itself, require the installation of a traffic control signal" and that a "traffic control signal should not be installed unless an engineering study indicates that installing a traffic control signal will improve the overall safety and/or operation of the intersection."

Capacity analysis (e.g., the methods in the TRB Highway Capacity Manual) and simulation can be beneficially used in these engineering studies to assess the operational impact of a traffic control signal, but practitioners would appreciate guidance on how best to use them. Sometimes, these tools may show that while the warrants are met, a location would operate more effectively without a traffic control signal. This guidance should enhance the decision-making process and reduce inappropriate installations of traffic control signals.

The objective of this research was to develop a user's guide for using capacity analysis and simulation in engineering studies to determine the appropriateness of traffic control signal installations. The research included the following tasks: (1). Identify traffic and roadway conditions that are problematic when applying traffic signal warrants and determining the appropriateness of a traffic control signal. (2). Describe how capacity analysis and simulation are applicable to the process of assessing the need for a traffic control signal. Identify operational measures of effectiveness that should be considered in this assessment. (3). Based on the results of Tasks 1 and 2, develop a detailed outline of the user's guide that demonstrates the use of capacity analysis and simulation in determining the need for a traffic control signal. The outline should demonstrate how the guide will be used to compare traffic control signals with other types of traffic control and other remedial measures. It is expected that specific case studies will be used to illustrate the application of these guidelines. (4). Submit an interim report to document Tasks 1 through 3 for review by the NCHRP. If applicable, deficiencies in the MUTCD warrants and suggested approaches to addressing them should be identified in the report. (5). Develop a clear, concise user's guide for use by traffic practitioners based on the outline approved by the NCHRP. (6). Develop recommended text for specific modifications to the MUTCD. (7). Submit a final report that documents the entire research effort and includes the Task 5 user's guide as a stand-alone document.

Status: The project is complete.

Report Availability: The report has been published as NCHRP Report 457, "Evaluating Intersection Improvements: An Engineering Study Guide." An enhanced online version of the report is available at
http://onlinepubs.trb.org/onlinepubs/nchrp/esg/esg.pdf and a ZIP file containing referenced spreadsheets is available at http://onlinepubs.trb.org/onlinepubs/nchrp/esg/ESG-Spreadsheets.zip

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