Best Practices for Roundabout and Alternative Intersection/Interchange Lighting

Alternative (or innovative) intersections and interchanges are junctions of two or more roads that do not use traditional intersection or interchange layouts. Most alternative intersections/interchanges installed in the United States have roadway lighting, in part because lighting is supported by FHWA’s Alternative Intersection and Interchange Report and NCHRP Report 672: Roundabouts: An Information Guide. However, lighting adds significantly to the upfront construction cost and ongoing maintenance costs, which can be a barrier to successful implementation. Lighting can also be a barrier to implementing projects where local communities are concerned about light pollution or trespass. Some agencies have a formal or informal policy that alternative intersections/interchanges must be lit, but do not necessarily light traditional signalized intersections(a policy that may be backwards given that traditional signalized intersections typically have a greater number of conflict points for pedestrians and vehicles than alternative intersections/interchanges). The objective of this research is to provide answers to the following questions: (1) What safety benefits can lighting provide for motorists and pedestrians at various alternative intersection/interchange types? (2) Can criteria be established that prioritizes what characteristics of alternative intersections/interchanges most strongly warrant lighting? Example criteria might include number of lanes (e.g., multilane vs. single-lane roundabouts), presence of pedestrian or bicycle facilities, etc. (3) What are best practices for lighting design of alternative intersections/interchanges? (4) For some junction types, lighting has been recommended to reduce risk of wrong-way entry, for example going clockwise in a roundabout or entering wrong-way on a diverging diamond interchange. Does lighting provide measurable benefit in reducing risk of such maneuvers? Note that for alternative interchanges, wrong-way entry risk may be lower than it is at traditional diamond interchanges. Potential research activities include (1) literature review; (2) survey of current state practices, and practices in other countries where roundabouts are more common than in the United States; (3) review crash data for existing alternative intersections/interchanges with and without lighting; (4) driver simulation analyses of various alternative intersection/interchange types with and without lighting, and with different lighting strategies; and (5) develop conceptual layouts showing recommended pole/luminaire placement for common alternative intersection/interchange types. The primary final product would be suggested revisions to the AASHTO Roadway Lighting Design Guide.


  • English


  • Status: Proposed
  • Funding: $500000
  • Contract Numbers:

    Project 05-27

  • 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:

    Retting, Richard

  • Start Date: 20220607
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01847360
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 05-27
  • Files: TRB, RIP
  • Created Date: May 23 2022 3:03PM