Assessing the Multi-Modal Safety Performance of Turn Lanes

Turn lanes typically are installed on highways and arterial roads at intersections to improve motor vehicle traffic operations and safety performance. While motor vehicle safety is a factor in determining where and when the installation of turn lanes may be appropriate, experience has shown that crash experience at some intersections may increase following the installation, as well as increase the exposure of other modes of travel to conflicts, time to cross an intersection, and therefore increased crash potential. Furthermore, considerations of crash risks associated with pedestrian and bicycle traffic at intersections are not explicitly considered by many designers and traffic operations professionals. In addition, little guidance and no models are available for designers and safety professionals, (e.g., the AASHTO Highway Safety Manual (HSM), the Manual of Uniform Traffic Control Devices (MUCTD), state and local highway design guides, and the AASHTO Policy on Geometric Design for Highways and Streets). Ongoing and recently completed NCHRP research is expanding the range of intersection types addressed by crash prediction methods in Chapters 10, 11, and 12 of the HSM and the scope of pedestrian and bicycle safety performance functions (SPFs) that practitioners can use to include these travel modes in safety analyses of intersections. (NCHRP Projects 17-68 and 17-84 are reviewing intersections and bicyclist and pedestrian safety respectively). Research is needed to extend this research to include multimodal safety performance and design considerations at intersections with turn lanes. NCHRP has determined that building directly on preceding research, particularly utilizing previously collected data and applying analysis methods from this preceding research will be cost-effective and otherwise very advantageous to NCHRP and the program’s sponsors. The objective of this research is to advance practices by characterizing the typology and turn-lane configurations and associated motor vehicle, bicycle, and pedestrian turn-lane crash risks and developing SPF and CMFs for a selection of configurations as limited by current budget develop safety performance functions (SPFs) and Crash Modification Factors (CMFs) using predictive (preferred) or risk-based methods for considering motor vehicle, pedestrian, and bicycle traffic and their interactions at intersections with turn lanes with different volume and intersection (e.g, number of lanes, signal operations, crossing width) characteristics. The research results should be useful to safety practitioners at state and local levels responsible for design and safety analysis of needs for and specific designs of such intersections. The research should provide a methodology to determine the changes in the crash potential for bicyclists and pedestrians and be useful in determining operational and safety performance tradeoffs between vehicles, bicyclists, and pedestrians. The research will provide guidance on how to perform and apply the tradeoff analysis as part of the design decision-making process. The research results should be suitable for inclusion in the HSM and other appropriate guidance used by such practitioners.


  • English


  • Status: Proposed
  • Funding: $400000
  • Contract Numbers:

    Project 07-28(02)

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001
  • Project Managers:

    McKenney, Christopher

  • Start Date: 20230529
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01879057
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 07-28(02)
  • Files: TRB, RIP
  • Created Date: Apr 10 2023 5:14PM