Innovative intersections and interchanges are junctions of two or more roads that do not use traditional intersection or interchange layouts. Examples include diverging diamonds, restricted crossing U-turns, displaced left turns, and roundabouts. Most innovative intersections/interchanges installed in the United States have roadway lighting, in part because lighting is supported by Federal Highway Administration’s (FHWA’s) Alternative Intersection and Interchange Report, and NCHRP Report 672: Roundabouts: An Informational Guide, second edition. Lighting, however, adds significantly to construction and maintenance costs, which can be a barrier to constructing roundabouts and other innovative intersections/interchanges. Research is needed to help practitioners determine what factors, in addition to safety, should be considered when designing lighting at these locations, such as social, environmental, economic impacts, maintenance, constructability, community concerns, and light pollution.
The objective of this project is to develop a practitioners’ guide for lighting at innovative intersections/interchanges, including roundabouts that (1) documents quantitative safety benefits associated with lighting for motorists and vulnerable road users (e.g., motorcyclists, pedestrians, bicyclists) at innovative intersections/interchanges; (2) establishes evidence-based criteria for determining whether or not to install lighting; and (3) identifies best practices, noteworthy considerations, and emerging approaches for lighting design at innovative intersections/interchanges, including roundabouts.
The research plan should (1) include a kick-off teleconference with the research team and NCHRP convened within 1 month of the contract’s execution; (2) address how the proposer intends to satisfy the project objective; (3) be divided logically into detailed tasks necessary to fulfill the research objective and include appropriate milestones and interim deliverables; and (4) incorporate opportunities for the project panel to review, comment on, and approve milestone deliverables.
Accomplishment of the project objective will require at least the following tasks.
Task 1. Conduct a review and synthesis of domestic and international literature related to lighting at innovative intersections/interchanges, including roundabouts.
Task 2. Conduct a review of current state practices related to lighting at innovative intersections/interchanges, including roundabouts, as well as practices in other countries where roundabouts are more common. As part of this task, the selected research agency should review and reference relevant findings from NCHRP Synthesis 575: Lighting Practices for Isolated Rural Intersections to avoid redundancy with that research effort. The review should include available information regarding additional measures used by states, beyond lighting, to enhance nighttime visibility at innovative intersections/interchanges, including roundabouts, such as raised pavement markers, illuminated bollards, in-pavement lighting, and LED-lighted warning signs.
Task 3. Collect available safety data for innovative intersections/interchanges, including roundabouts, with varying characteristics and lighting conditions.
Task 4. Identify gaps, inconsistencies, and conflicts in the current state of practice and available safety data. These gaps should be addressed in the final product or in the recommended future research, as budget permits.
Task 5. Develop a methodology for conducting a safety analysis for innovative intersections/interchanges, including roundabouts, with varying characteristics and lighting conditions.
Task 6. Propose a preliminary outline for the guide.
Task 7. Prepare Interim Report No. 1 that documents the work completed in Tasks 1 through 6. The updated plan must describe the work proposed for Phase II.
Task 8. Conduct Task 5 according to the approved Interim Report No.1.
Task 9. Develop a practitioners’ guide for lighting at innovative intersections/interchanges, including roundabouts, which should include:
- Criteria for determining under what conditions lighting is justified in furtherance of roadway safety.
- Lighting design considerations and suggested lighting levels based on geometry, land use, presence of vulnerable road users, and other factors.
- Conceptual lighting layouts showing suggested pole/luminaire placement for common types of roundabouts and other innovative intersections/interchanges.
- Identify and briefly discuss other issues practitioners should consider such as social, environmental, and economic considerations, maintenance and constructability, community concerns, and light pollution. Details studies are not required.
- Additional measures to enhance nighttime visibility at innovative intersections/interchanges, including roundabouts (as noted in Task 2).
The guide should focus on common types of innovative intersection/interchanges and only briefly discuss considerations for other less common types such as echelon interchanges, turbo roundabouts, and mini roundabouts, which generally are located along urban, lighted corridors.
Task 10. Develop a site-specific decision-making tool for use by practitioners in determining (1) under what conditions lighting is justified; (2) if justified, what best lighting design practices are suggested; and (3) if not justified, what other types of measures can be implemented to enhance nighttime visibility.
Task 11. Conduct a workshop with at least 15 representatives of state departments of transportation to demonstrate and collect feedback on the guide and draft decision-making tool. Revise the guide and draft decision-making tool and workshop materials taking into account feedback gathered during the workshop.
Task 12. Prepare a final deliverable that documents the entire research effort. Final deliverables should include, at a minimum (1) a final research report documenting the entire research effort and findings; (2) a practitioners guide to best practices for lighting at innovative intersections/interchanges, including roundabouts; (3) a decision-making tool; (4) prioritized recommendations for future research; (5) presentation material; and (6) technical memorandum on implementation (see Special Note I).
STATUS: A response has been received for this RFP. The project panel will meet to determine next steps.