Design Guidance for Freeway Mainline Ramp Terminals

The design values for freeway ramps in the AASHTO Policy on Geometric Design of Highways and Streets (Green Book) rely heavily on research conducted in the late 1930s and early 1940s, predating the development of the Interstate system. The studies relied entirely on passenger cars for acceleration and deceleration rates, without consideration of trucks and busses; this was based on the assumption that the acceleration distances for heavy vehicles would be "entirely out of reason." Vehicle characteristics have changed since the original research. For example, the weight-to-horsepower ratio for trucks in 1965 was 400 lb/hp compared with the currently used ratio of 200 lb/hp. According to the Green Book, the mainline terminal of a ramp is that portion adjacent to the through traveled way, including speed-change lanes and tapers. There are two basic designs for freeway ramp terminals: tapered and parallel. Transportation agencies tend to adopt one of these designs as a standard (often different for entrances and exits), but there is little objective information available for designers on their relative strengths. The objective of this research is to develop improved design guidance for freeway mainline ramp terminals suitable for inclusion in the AASHTO Green Book. As appropriate, the guidance should also address issues related to the design of the gore area and any transitional area to the ramp proper.


  • English


  • Status: Completed
  • Contract Numbers:

    Project 15-31

  • Sponsor Organizations:

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  USA  20590

    American Association of State Highway & Transportation Officials

    444 North Capitol Street, NW, Suite 225
    Washington, DC    20001

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  USA  20001
  • Project Managers:

    Derr, B

  • Performing Organizations:

    CH2M Hill, Incorporated

    8501 W. Higgins Road, Suite 300
    Chicago, IL  USA  60631-
  • Principal Investigators:

    Antonucci, Nick

  • Start Date: 20050127
  • Actual Completion Date: 20070426
  • Source Data: RiP Project 10639

Subject/Index Terms

Filing Info

  • Accession Number: 01460722
  • Record Type: Research project
  • Source Agency: National Cooperative Highway Research Program
  • Contract Numbers: Project 15-31
  • Files: RiP, USDOT
  • Created Date: Jan 3 2013 1:31PM