Design Options to Reduce Turning Motor Vehicle Conflicts with Bicyclists and Pedestrians at Intersections

More than 4,000 pedestrians and 700 bicyclists were killed in collisions with motor vehicles in the United States in 2012. Each year, many more pedestrians and bicyclists have their jobs, financial security, and physical capabilities changed permanently as a result of non-fatal crashes. The most common location for these collisions is at intersections. By way of example, a nine-year analysis of bicycle crash types in Cambridge, MA showed that over 60% of bicycle/motor vehicle crashes occurred at intersections. In addition, 56% of pedestrian crashes in Alameda County, CA occurred at or within 50 feet of an intersection. Signalized intersections are particularly important locations for safety improvements: an extensive pedestrian safety analysis in New York City found that nearly half (47%) of pedestrian fatalities and severe injuries occurred at signalized intersections. Improving bicycle facilities at intersections is clearly a critical safety topic, and several common types of bicycle crashes have been identified in previous studies. Of particular concern for bicyclist safety at intersections is the conflict between bicyclists traveling straight and automobiles from the opposite direction turning left across the path of bicyclists. In addition, there are often conflicts between bicyclists traveling straight and automobiles from the same direction turning right across the path of bicyclists. A third common type of bicycle crash involves motorists emerging from side streets and driveways (which are a kind of minor intersection) and not yielding to through-moving cyclists. There are also several common types of pedestrian crashes. These often occur at intersections that involve automobiles turning left and striking pedestrians in the far crosswalk and automobiles turning right and striking pedestrians in the near or far crosswalk. This includes situations where drivers are allowed to make a right turn on red. Despite the widespread acknowledgment of these problems, transportation engineers and planners still lack definitive guidance on which types of designs have the greatest safety benefits. For example, current design practices commonly drop bicycle pavement markings and signs at intersections, providing little or no positioning guidance for motorists or bicyclists. Meanwhile, some more recent guidance suggests options such as dashing or coloring through the intersection. Some intersections fail to provide crosswalks or pedestrian signals, leaving motorists and pedestrians to rely on their best guess as to what the other user will do. In addition to these ambiguous situations, there are a number of design choices that may directly impact pedestrian or bicycle safety: pedestrian signal phases may be shortened to their minimum required length, turning radii may be increased, or right-turn-on-red may be allowed in order to allow more automobiles to pass through the intersection, making it more difficult to cross the street as a pedestrian. These changes are often made without the most effective consideration of pedestrian safety. There is no comprehensive approach to indicate what designs provide the most effective approach or the most appropriate situation in which each should be applied. The primary guidance documents for practitioners, including the American Association of State Highway and Transportation Officials (AASHTO) Guide for the Development of Bicycle Facilities (2012), AASHTO Guide for the Planning, Design, and Operation of Pedestrian Facilities (2004), NACTO Urban Bikeway Design Guide (2011), Highway Capacity Manual (2010), Highway Safety Manual (2010), and Manual on Uniform Traffic Control Devices (2009), do not provide sufficient information about the strategies that are most effective in specific circumstances. Engineering judgment will still be needed in many cases, but better guidance for applying typical and innovative intersection design treatments will help improve pedestrian and bicycle safety. The objective of this research is to develop guidance for intersection design that minimizes the risk of motor-vehicle turning conflicts with pedestrians and bicyclists. The following tasks are expected: (1) identify typical and innovative design treatments to improve the safety of bicyclists and pedestrians at signalized intersections; (2) identify prevalent motor vehicle/bicycle and motor vehicle/pedestrian crash types at signalized intersections and identify specific differences in different settings (urban, suburban, rural); (3) conduct conflict studies at intersection approaches with and without the following design elements: for bicycles, standard bicycle lanes; marked/dashed bike lane/bike travel path through intersections; colored pavement for bike travel paths through intersections; bike boxes; bicycle signal-heads with accompanying bicycle-specific signal phasing; physical separation of bicycle facilities; and exclusive right-turn lanes for automobiles; for pedestrians, pedestrian signals with and without leading pedestrian intervals; curb extensions; reduced curb radius; prohibit right-turn-on-red; and pedestrian crossing islands; (4) document safety impacts of various design treatments observed; and (5) a practitioner's reference for effective accommodation of bicycles and pedestrians at intersections. This reference will synthesize existing information in the common manuals mentioned above and add relevant results from research providing practitioners with documentation to improve designs of intersections for multiple users. A key outcome of this research is the ability to determine those intersection designs that provide the most effective means of improving bicycle safety for specific situations and environments. Note that the conflict studies will not be expected to produce crash modification factors (CMFs) since it is unlikely that there will be sufficient data to draw strong conclusions. However, the conflict studies will provide a basis for future data collection and more rigorous studies that produce CMFs.


  • English


  • Status: Proposed
  • Contract Numbers:

    Project 15-63

  • Sponsor Organizations:

    Federal Highway Administration

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

    American Association of State Highway & Transportation Officials

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

    National Cooperative Highway Research Program

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

    Rogers, William

  • Start Date: 20150806
  • Expected Completion Date: 0
  • Actual Completion Date: 0
  • Source Data: RiP Project 40212

Subject/Index Terms

Filing Info

  • Accession Number: 01572387
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 15-63
  • Files: TRB, RiP
  • Created Date: Aug 7 2015 1:01AM