Design Guidance for Interchange Loop Ramps

Interchanges are among the most complex and expensive components of the roadway network. An appropriate interchange design must safely and effectively accommodate the traffic volumes for the various movements, while considering the context of the location (e.g., rural/urban, right-of-way and environmental constraints, near-by traffic generators, upstream and downstream interchanges). Design decisions can be even more difficult when improving an existing interchange. Several interchange designs have been developed over the years, using a variety of ramp types and connections from the ramps to the intersecting roadways. Loop ramps are prominent in the traditional cloverleaf design and are also used in partial cloverleafs, trumpets, and other interchange designs. Despite their long use, information on the safety and operational performance of loop ramps is limited. This is particularly true for two-lane loop ramps because of the interactions between passenger vehicles and trucks traveling side-by-side on a fairly tight curve. In addition to conditions on the ramp proper, the safety and operation of the connections from the ramp to the intersecting roads must be considered. For freeway connections to and from a multi-lane ramp, the development or termination of the added lanes must be carefully designed to adequately accommodate diverging/merging movements and the necessary deceleration/acceleration. When a loop ramp terminates at a traffic signal or a ramp meter, the design must consider the expected queue. The objective of this research is to develop improved design guidance for interchange loop ramps and their connections. The guidance should consider the context of the interchange and the safety, operational, and constructability impacts of the design.


  • English


  • Status: Proposed
  • Funding: $450000.00
  • Contract Numbers:

    Project 03-105

  • Sponsor Organizations:

    Federal Highway Administration

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

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    National Cooperative Highway Research Program

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

    Derr, B

  • Start Date: 20111130
  • Expected Completion Date: 0
  • Actual Completion Date: 0
  • Source Data: RiP Project 28998

Subject/Index Terms

Filing Info

  • Accession Number: 01463296
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 03-105
  • Files: TRB, RiP, USDOT
  • Created Date: Jan 3 2013 2:21PM