Intersection Safety Case Study Summary

1. Intersection Safety Case Study Summary Signalized Intersections:Permissive/Protected Left-Turn Phasing A Michigan Success Story FHWA-SA-09-015

2. The Challenge About 27% of all intersection crashes in the United States are associated with left turns with over two-thirds occurring at signalized intersections1. Left turn movements introduce risk of vehicle conflicts. Several intersection treatments have been developed to reduce these risks, including converting from a permissive left-turn mode to permissive/protected phasing. The Cities of Detroit and Grand Rapids sought to reduce these risks,and the number and severity of crashes, at signalized intersections. 1. California Center for Innovative Transportation, August 2004.

3. Solution Permissive/Protected left-turn phasing: Steady green signal provides permissive phasefor left-turns Left-turn arrow provides exclusive, protected phase for left-turns in the same cycle MUTCD (Section 4D.06) provides standards and applications

4. Technical Data Location: 3 high-crash locations in the cities of Detroit and Grand Rapids, Michigan Speed Limits: Ranged from 30 mph to 35 mph Implementation Cost: $25,000 per intersection Implementation Time: 1 week per intersection Implementation Issues: No implementation issues were experienced with these countermeasures.

5. Results at Treated Intersections Average Crash Reductions: 84% reduction in left-turn head-on crashes per year 58.9% reduction in injury crashes per year 32% reduction in total crashes per year

6. For More Information Visit FHWA’s intersection safety web site to download this and other case studies highlighting proven intersection safety treatments from across the country: http://safety.fhwa.dot.gov/intersection/ Or contact: Tapan Datta Transportation Research Group Wayne State University Phone: (313) 577-9154 E-mail: tdatta@eng.wayne.edu Ed Rice Office of Safety (HSSD) Federal Highway Administration Phone: (202) 366-9064 E-mail: ed.rice@dot.gov