Intersection crashes represent a significant portion of total crashes nationwide; they account for an average of 9,000 fatalities and 1.5 million injuries annually. Fatalities and severe injuries are more likely to occur in high-speed environments of mostly rural and suburban/urban intersections.
FHWA and AASHTO recently sponsored a European scanning tour focused on innovative safety practices in the planning, design, operation, and maintenance of signalized intersections. The scanning team visited several European countries and developed an implementation plan with five major recommendations. One recommendation in the plan was for development of treatments that reduce speeds at the approaches to and through intersections.
Roundabouts have been credited with significant safety improvements because they force drivers to slow down and they reduce conflicts. At conventional intersections, it should be possible to develop innovative treatments that reduce speeds and that have a significant impact in reducing injuries and fatalities to all users.
The objectives of this project were to (1) identify or develop treatments and (2) develop guidelines for their selection to reduce the operating speed of vehicles approaching intersections, thereby reducing the frequency and severity of crashes.
For the purpose of this project, the research focused on at-grade, signalized and unsignalized intersections with operating speeds of 45 mph or greater, and on treatments that focus on geometric design and other physical features, but also include consideration of traffic signs and pavement markings.
The research included the following tasks:
PHASE I (1.) Analyze, describe, and critique pertinent domestic and international research, current practice, and statistical databases related to the frequency and severity of crashes at intersections and treatments to reduce vehicle speeds. (2.) Identify the types and characteristics of intersections that show high risk and severity of accidents where a reduction of operating speed is likely to result in crash reductions. (3.) Identify or recommend specific treatments that show the most promise to reduce vehicle operating speeds at approaches to intersections. (4.) Prepare an initial outline of the proposed format for guidelines on the selection of speed reduction treatments. (5.) Develop a plan to evaluate the most promising treatments through field tests and/or computer simulations in Phase 2. This evaluation should focus on new or innovative treatments that have not been fully evaluated in other studies. It is anticipated that some of the field testing may require partnering with state or local highway agencies to evaluate existing speed reduction treatments, or to install and evaluate new treatments. (6.) Submit an interim report, within 9 months, to document Tasks 1 through 5 for review by the NCHRP.
PHASE II (7.) Initiate the field testing or simulation studies as approved by the NCHRP. (8.) Based on the results of Tasks 1 through 6 and preliminary results of Task 7 testing, develop draft guidelines for the selection of speed reduction treatments. The guidelines should incorporate the best available information from existing research and Task 7 findings. (9.) Submit a second interim report within 24 months to document the preliminary results of Tasks 7 and 8 for review by the NCHRP. The contractor will be expected to meet with the NCHRP panel approximately 1 month later. (10.) Revise the draft guidelines as necessary based on the field test results and the NCHRP review comments. (11.) Submit a final report that documents the entire research effort and includes the Task 10 guidelines as a stand-alone document. In addition, provide a companion executive summary and PowerPoint presentation that outlines the project background, methodology, findings, and recommendations.
Product Availability: The guidelines (NCHRP Report 613) and final report (NCHRP Web-Only Document 124) are available in the TRB Bookstore.