Design Options to Reduce Turning Motor Vehicle–Bicycle Conflicts at Intersections

Each year, vehicle–bicycle collisions result in hundreds of cyclist deaths and many more non-fatal injuries (the exact numbers are difficult to define because of inconsistent reporting methods). The most common location for these collisions is at intersections, which inherently have a large number of turning conflicts. Reducing these conflicts is a key objective in improving intersection safety across all modes. Of particular concern for bicyclist safety at intersections are the conflicts between straight-through bicyclists and motor vehicle right-turns and opposing left-turns. Despite the widespread acknowledgement of this problem, transportation engineers and planners still lack definitive guidance on how to safely and effectively design for bicycles at intersections in the United States. Thus, research on effective methods to reduce these conflicts, with accompanying intersection design guidance, is a high priority. The primary guidance documents for practitioners, including the AASHTO Guide for the Development of Bicycle Facilities and the NACTO Urban Bikeway Design Guide are often based on professional judgment rather than research. Research-based guidance tends to be more general, such as providing countermeasure options, but not specific design guidance (e.g., as in the forthcoming NCHRP 15-63 Improving Pedestrian and Bicyclist Safety at Intersections guidance and BikeSafe). Current design practices often drop bicycle pavement markings and signs at intersections, providing no positioning guidance for motorists or bicyclists—a practice that has led to confusion in some states as to who has the right-of-way through the intersection. Alternatively, other jurisdictions continue bicycle lane markings all the way through intersections; in others, the lanes are dashed. Moreover, innovative treatments including bike boxes, use of color, bicycle signals, and separated crossings are increasing across the country, and while some of these have been examined through research studies, their effectiveness is inconclusive. Research on alternative designs to reduce conflicts at intersections is required to determine best practices to meet these objectives. The objective of the research is to develop guidelines for intersection design that minimizes the risk that motor-vehicle turning movements create for through-moving bicyclists. To accomplish this, the research should rely on conflict data to supplement often-sparse crash data. The research, at a minimum, will: 1. Identify typical and innovative design treatments for bicyclists at signalized intersections. 2. Identify prevalent motor vehicle–bicycle crash types at signalized intersections. 3. Conduct conflict studies at signalized four-way intersection approaches with and without the following design elements: - Bike lanes - Exclusive turn lanes - Marked/dashed bike lane/bike travel path through intersections - Colored pavement for bike travel paths through intersections - Separate stop bar locations for motor vehicles and bicycles - Bike boxes - Alternative methods to accommodate bicycle left-turns - Bicycle signal-heads with accompanying bicycle specific signal phasing - Physical separation of bicycle facilities - Other relevant pavement markings, signs, and signal designs. 4. Document safety impacts of various design treatments observed. 5. Summarize research results in a practitioner’s guide for effective accommodation of bicycles at intersections.


  • English


  • Funding: $600,000
  • Contract Numbers:

    Project 15-73

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    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
  • Project Managers:

    Rogers, William

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

Subject/Index Terms

Filing Info

  • Accession Number: 01707631
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 15-73
  • Files: TRB, RiP
  • Created Date: Jun 3 2019 3:17PM