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. Motor vehicle safety is a primary motivation in determining where and when installation of turn lanes may be appropriate, but experience has shown that crashes at some intersections may increase following the installation, for example, vehicles queued in the turn lane may obstruct the drivers’ view from vehicles crossing on the minor road. In addition, bicycle and pedestrian traffic face increased conflict and crash potential when turns are introduced. Currently available guidance documents—for example the American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual (HSM), the Manual on Uniform Traffic Control Devices (MUTCD), state and local highway design guides, and the AASHTO Policy on Geometric Design for Highways and Streets—offer little assistance to designers and traffic operations professionals for dealing with safety for turn lanes, and there are no generally accepted models for assessing multimodal crash risks at intersections with turn lanes. Ongoing and recently completed NCHRP research is expanding the range of intersection types addressed by crash prediction methods presented in the HSM (in Chapters 10, 11, and 12), and developing safety performance functions (SPFs) and crash modification factors (CMFs) for addressing pedestrian and bicycle safety at intersections (e.g., NCHRP Projects 17-68 and 17-84). However, further work is needed to provide tools for assessing comprehensively multimodal design considerations and safety performance at intersections with turn lanes. Building directly on preceding research, particularly utilizing previously collected data and applying analysis methods from this preceding research, will be cost-effective and very advantageous to state departments of transportation (DOTs). The objective of this research is to develop (1) SPFs and CMFs to support safety assessment and design decision-making for installation and management of turn lanes at intersections, (2) documentation of this information in forms usable by safety and design practitioners, and (3) guidelines for using the information to perform intersection safety assessments. The research will necessarily entail development of a typology of intersections and turn-lane configurations and application of models for assessing multimodal crash risk as a function of geometric and operational parameters at an intersection. The research results should be useful to responsible state- and local-level practitioners and suitable for inclusion within currently used guidance materials such as the HSM and design guides.  


  • 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: 20240214
  • 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