Research for AASHTO Standing Committee on Highways. Task 405. Reevaluation of the Perception and Reaction Time and Deceleration Rates for Stopping

The AASHTO Subcommittee on Highways issued a resolution on Flexibility in Design Standards. The current minimum Stopping Sight Distances (SSDs) in AASHTO’s A Policy for Geometric Design of Highways and Streets, 2011 (a.k.a. Green Book) are not threshold values and substantial deviations can be made without impacting crash rates or severity. The very conservative SSD criteria result in lengthy minimum sight distances, which reduce the flexibility for the design and can result in additional costs, additional use of resources, and design exceptions with no apparent safety benefit. SSD is one of the 10 Controlling Design Parameters established by FHWA and should represent a safety threshold. The research objective is to determine a cost-effective SSD model for 2R/3R, Reconstruction, and New Construction Projects and revised text for an update of the AASHTO Green Book.


  • English


  • Status: Terminated
  • Contract Numbers:

    Project 20-07, Task 405.

  • 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
  • Start Date: 20210907
  • Expected Completion Date: 0
  • Actual Completion Date: 20210907

Subject/Index Terms

Filing Info

  • Accession Number: 01781398
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 20-07, Task 405.
  • Files: TRB, RIP
  • Created Date: Sep 7 2021 1:36PM