Procedure for Determining Work Zone Speed Limits

This NCHRP Digest summarizes the findings of NCHRP Project 3-41, “Procedure for Determining Work Zone Speed Limits”. The “Manual on Uniform Traffic Control Devices for Streets and Highways” has no uniform guidelines for determining work zone speed limits. At their 1988 joint meeting, the AASHTO Highway Subcommittee on Traffic Engineering and the Maintenance Technical Committee of the National Committee on Uniform Traffic Control Devices unanimously concurred that research was urgently needed to establish a procedure for determining work zone speed limits to address safety problems. The research reported here was initiated to meet this need. The researchers sought to answer three fundamental questions: (1) Are work zones with reduced speed limits safer’ (2) What are the compliance levels with various speed limit reductions’ and (3) What roadway and traffic factors should be considered in determining a work zone speed limit’ To answer these questions, Graham-Migletz Enterprises, Inc. (GME) conducted a literature review and interviewed state and local highway agency officials in 12 states to learn about the procedures their agencies used to establish work zone speed limits and the perceived effectiveness of various speed limit reduction policies. In addition, the research included interviews and surveys to determine the attitudes of motorists, construction contractors, and construction liability insurance carriers concerning how work zone speed limits should be set. The results were considered in planning field data collection on vehicle speeds, traffic accidents, and traffic conflicts in work zones. A candidate procedure for appropriate work zone speed limits was formulated early in the research and revised, as appropriate, throughout the remainder of the project.