Safety Effects of Protected and Protected/Permitted Left-Turn Phases

This project will estimate the safety effects of protected and protected/permitted left-turn phases for different intersection conditions and provide operational recommendations. Protected left-turn phases at signalized intersections are intended to reduce the frequency of angle collisions that result from conflicts between left-turning vehicles and opposing through vehicles. Various studies have demonstrated the overall safety effectiveness of protected left-turn phases (e.g., Harkey et al., 2008; Davis and Aul, 2007). The American Association of State Highway and Transportation Officials National Cooperative Highway Research Program (AASHTO’s NCHRP) 500 series also notes that the frequency of rear-end and sideswipe crashes between left-turning vehicles and following-through vehicles can also be reduced with properly timed, protected left turns. There is not a consensus on the extent of this safety effectiveness under different intersection conditions. While separate left-turn phasing may reduce delay for left-turning vehicles, it may increase the overall intersection delay and disrupt traffic progression. It is therefore important to understand the safety effects of protected left-turn phases under a variety of intersection conditions so that appropriate operational and safety trade-offs can be quantified and considered by agency decision makers. Protected/permitted left-turn phasing is sometimes used as a compromise between fully-protected and permitted only phasing. Information on the safety effects of protected/permitted under a variety of intersection conditions is needed as well. Intersection conditions of interest will be selected with input from the project’s technical advisory committee, but may include factors such as turning volumes, opposing through volumes, pedestrian crossing volumes, approach speeds, sight distance, number of lanes, and type of channelization.

    Language

    • English

    Project

    • Status: Active
    • Funding: $95000
    • Contract Numbers:

      15-9087

    • Sponsor Organizations:

      Utah Department of Transportation

      4501 South 2700 West
      Project Development
      Salt Lake City, UT  United States  84114-8380

      Mountain Plains Consortium

      Civil & Environmental Engineering
      122 S. Central Campus Drive
      Salt Lake City, UT  United States  84112-0561
    • Managing Organizations:

      Utah Department of Transportation

      4501 South 2700 West
      Project Development
      Salt Lake City, UT  United States  84114-8380
    • Project Managers:

      Nichol, Kevin

    • Performing Organizations:

      University of Utah, Salt Lake City

      College of Engineering, Department of Civil Engineering
      Salt Lake City, UT  United States  84112-0561
    • Principal Investigators:

      Porter, Richard

    • Start Date: 20150423
    • Expected Completion Date: 20170331
    • Actual Completion Date: 0

    Subject/Index Terms

    Filing Info

    • Accession Number: 01593651
    • Record Type: Research project
    • Source Agency: Utah Department of Transportation
    • Contract Numbers: 15-9087
    • Files: RiP, STATEDOT
    • Created Date: Mar 15 2016 3:56PM