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                Maryland Evaluates the Safety Benefits of Modern Roundabout Intersections Compared to Two-way Stop-controlled Intersections
**Publication Year:** 
            2010
    
        Original publication: Roundabouts – The Maryland Experience: a Maryland Success Story (FHWA-SA-09-018) (PDF, 548kB)

The National Highway Traffic Safety Administration (NHTSA) data show that approximately 733,000 people were injured and 7,196 were killed in intersection-related traffic crashes in 2008. The Maryland State Highway Administration (MDSHA) was concerned about the high number of crashes at some of its intersections controlled by two-way stop signs.

Recognizing that high approach speeds coupled with drivers violating stop-controls can result in crashes, MDSHA converted five rural, two-way stop-controlled intersections experiencing a high incidence of crashes, many with injuries, to single-lane roundabout intersections.
"Photograph of a warning sign showing counterclockwise rotating arrows that indicate a roundabout is ahead"Figure 1:   Roundabout warning sign*Source: Maryland State Highway Administration (used with permission)*
"Diagram showing the eight potential vehicle conflict points on a standard two-lane roundabout"Figure 2:   Eight vehicle conflict points*Source: FHWA Roundabouts: An Informational Guide*
""Diagram showing the 32 potential vehicle conflict points on a standard two-lane roundaboutFigure 3:   32 vehicle conflict points*Source: FHWA Roundabouts: An Informational Guide*

Key Accomplishments

As the Maryland experience demonstrates, roundabouts can effectively improve safety and reduce traffic crashes and their resulting injuries and/or fatalities.

Results

The roundabouts installed at these Maryland stop-controlled intersections cumulatively reduced total crashes by approximately 69.1 percent and injury crashes by 88 percent in a three-year period after the roundabouts were installed. During this same period, the fatal crashes were eliminated, falling from three under the stop-controlled intersection design to zero after the roundabouts were installed.

Contact

Mike Niederhauser
Maryland State Highway Administrationtmniederhauser@sha.state.md.us U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

202-366-4000Subscribe to email updates
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