Relationship of Speed, Roadway Geometrics, and Crashes on High-Speed Rural Highways

Understanding the speed-crash relationship has long been of interest in roadway safety analysis. But the relationship cannot be adequately established without taking into account the many factors that influence both speed and crashes: roadway geometry and context, weather conditions, human factors, vehicle type distribution, and the dynamics of the vehicle and tire. While a significant amount of research has been conducted to identify relationships between roadway design elements and crashes, research that has also considered the contribution of operating speeds or posted speed is limited. A general subjective understanding of the contribution of operating speed of a highway or freeway, through the dynamics of the vehicle, on the severity of a crash is known: higher speeds are associated with more severe crashes. What is desired is a quantitative understanding of how speed (operating and posted) in conjunction with roadway geometry relates to the likelihood of a crash and to crash severity. This research would build on existing research to explore the relationships between roadway geometrics, speed (operating and posted), and crashes on high-speed rural highways. These relationships will help inform future design guidelines, posted speed practices, and potential safety countermeasures, which are related to desired outcomes for multiple American Association of State Highway and Transportation Officials (AASHTO) committees, such as design, traffic engineering, and safety. The objective of this research is to explore the relationships between roadway geometrics, operating speed (as defined in FHWA-SA-10-001), posted speed, and crashes on high-speed rural highways. At a minimum, the research team shall: (1) Identify the relationships between speed (operating and posted), geometric characteristics, and crashes on high-speed rural highways, considering other design elements and road conditions. (2) Determine the relative contribution of speed (operating and posted) with various roadway geometric characteristics to crashes (in terms of frequency and severity) for high-speed rural highways. (3) Identify and measure the effectiveness of existing mitigation strategies for crashes and speed (operating and posted) on high-speed rural highways. (4) Determine if existing crash modification factors (CMFs) for geometric elements can be modified with a speed component, and if speed-related CMFs can be developed that could ultimately be incorporated into the AASHTO Highway Safety Manual (HSM) Part C.


  • English


  • Status: Proposed
  • Funding: $750000
  • Contract Numbers:

    Project 15-82

  • 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:

    Deng, Zuxuan

  • Start Date: 20230515
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01846129
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 15-82
  • Files: TRB, RIP
  • Created Date: May 23 2022 4:12PM