Crash-Modification Factor for Trees on Two-lane Rural Roads

Rural roads account for about one-third of the vehicle-miles traveled in Arizona but see more than half of the state's traffic fatalities. Five-year statistics show that a vehicle occupant hurt while colliding with a fixed object is twice as likely to die if the collision is on a rural road rather than an urban road. Among such fixed objects are trees beside two-lane rural highways. A systematic assessment of countermeasures for vehicle-tree collisions on such highways is needed. The crash modification factor (CMF), a multiplicative factor used to compute the expected number of crashes after implementing a given countermeasure at a specific site and maintained at the Crash Modification Factors Clearinghouse, though tabulated in the Highway Safety Manual (HSM) for roadside fixed objects along urban and suburban arterials, does not presently extend to roadside fixed objects, including trees, on two-lane rural highways. This study will determine the needed CMSs by finding any existing, pertinent CMFs in the literature even beyond the HSM and Clearinghouse; determining the data and analysis needed to develop CMFs for countermeasures along two-lane rural highways; recommending a data collection plan; and performing a statistically sound pilot before-and-after evaluation of countermeasures.


    • English


    • Status: Completed
    • Funding: $90000.00
    • Contract Numbers:


    • Sponsor Organizations:

      Federal Highway Administration

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

      Arizona Department of Transportation

      206 South 17th Avenue
      Phoenix, AZ  United States  85007
    • Project Managers:

      Gurrola, Javier

    • Performing Organizations:

      Cambridge Systematics

      555 12th Street
      Suite 1600
      Oakland, CA  United States  94607
    • Principal Investigators:

      Wemple, Beth

    • Start Date: 20120701
    • Expected Completion Date: 0
    • Actual Completion Date: 20150630
    • Source Data: RiP Project 31966

    Subject/Index Terms

    Filing Info

    • Accession Number: 01566106
    • Record Type: Research project
    • Source Agency: Arizona Department of Transportation
    • Contract Numbers: 721
    • Files: RiP, STATEDOT
    • Created Date: Jun 10 2015 1:01AM