Proposing New Speed Limit in Mountainous Areas Considering the Effect of Longitudinal Grades, Vehicle Characteristics, and the Weather Condition

The current method of Green book (AASHTO 2011) for assigning design speed (and consequently for speed limit) of roads is based on a point-mass model. Therefore, many effective variables such as longitudinal grades, vehicle characteristics, and weather condition are ignored. This fact creates serious safety problems in mountainous areas since, where these missing parameters are dominant. The condition becomes even worse because many of the mountainous roads were built many years ago based on the old design methods (for example, with the downgrades sharper than 10%). This project seeks to study the effect of different parameters related to geometric features (including the radius of the horizontal curve, superelevation rate, and longitudinal grade), vehicles characteristics (including type, weight, and the braking forces), and the weather condition (including side friction factor, wind speed, and wind direction). This analysis will be conducted using a comprehensive series of TruckSim and CarSim simulation tests on the most hazardous mountainous roads in Wyoming. Afterward, appropriate values of speed limit will be proposed for roads tested in the study. Also, new analytical models will be presented to be practical for the rest of the roads (not considered in the study) based on their geometric features, design vehicle, and weather condition.


  • English


  • Status: Active
  • Funding: $162424
  • Contract Numbers:


  • Sponsor Organizations:

    Office of the Assistant Secretary for Research and Technology

    University Transportation Centers Program
    Department of Transportation
    Washington, DC  United States  20590
  • Managing Organizations:

    Mountain-Plains Consortium

    North Dakota State University
    Fargo, ND  United States  58108
  • Project Managers:

    Kline, Robin

  • Performing Organizations:

    University of Wyoming

    Dept. of Civil and Architectural Engineering
    1000 E. University Avenue
    Laramie, WY  United States  82071
  • Principal Investigators:

    Molan, Amirarsalan Mehrara

    Alrejjal, Anas

    Ksaibati, Khaled

  • Start Date: 20180703
  • Expected Completion Date: 20220731
  • Actual Completion Date: 0
  • USDOT Program: University Transportation Centers Program
  • Source Data: MPC-574

Subject/Index Terms

Filing Info

  • Accession Number: 01674912
  • Record Type: Research project
  • Source Agency: Mountain-Plains Consortium
  • Contract Numbers: 69A3551747108
  • Files: UTC, RIP
  • Created Date: Jul 10 2018 9:33AM