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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation
FHWA Highway Safety Programs

Maryland Evaluates the Safety Benefits of Modern Roundabout Intersections Compared to Two-way Stop-controlled Intersections

Publication Year:

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 roundabout
Figure 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 Administration
tmniederhauser@sha.state.md.us