Safety Performance of Part-Time Shoulder Use on Freeways

"Safety Performance of Part-Time Shoulder Use on Freeways,” was to develop models and other quantitative tools for practitioners to evaluate safety performance of freeways with part-time shoulder use (PTSU) (including Bus on Shoulder (BOS)). The research is complete; it produced models that predict (1) the frequency of fatal-and-injury (FI) crashes and (2) the frequency of property damage only (PDO) crashes. These models were applied to assess the overall effect of PTSU on total and severe crash frequency. Models are available for basic freeway segments, entrance speed-change lanes, and exit speed-change lanes. A severity distribution function (SDF) also was developed to predict the distribution of FI crashes among different severity levels. Each model includes variables that describe the traffic demand characteristics, geometric elements, and PTSU operational features. This continuation request will support pilot testing of the PTSU models developed in Project 17-89 by state DOTs that operate such facilities with the goal of determining whether additional resources are needed to support wider-scale implementation through HSM2. The pilot tests will provide material for one or more case studies that will help practitioners use the research products. In addition, review of the pilot states’ efforts will help identify any Highway Safety Manual (HSM)-related needs, such as text to be included with the models, text for other sections of the HSM to explain the relationship to other models, training materials, etc. Subject to the availability of data, the participating state DOTs will run the models to: (1) estimate FI and PDO crash frequencies, compare them to DOT experience, and evaluate whether the models are suitable in their present form for incorporation in HSM2; (2) evaluate differences in safety performance between right- and left-side PTSU; and (3) conduct a before-after study of freeways where PTSU was implemented during NCHRP Project 17-89.


  • English


  • Status: Proposed
  • Funding: $125000
  • Contract Numbers:

    Project 17-89B

  • Sponsor Organizations:

    National Cooperative Highway Research Program

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

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Barcena, Roberto

  • Start Date: 20230702
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01873037
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 17-89B
  • Files: TRB, RIP
  • Created Date: Feb 13 2023 3:34PM