Traveling Maryland's Roundabouts
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Many studies have found that one of the benefits of roundabout installation is the improvement in overall safety performance. Several studies in the U.S., Europe, and Australia have found that roundabouts perform better in terms of safety than other intersection forms. In particular, singlelane roundabouts have been found to perform better than twoway stopcontrolled intersections in the U.S. Although the frequency of reported crashes is not always lower at roundabouts, reduced injury rates are typical. Safety is typically better at small and medium capacity roundabouts than at large or multilane roundabouts. While overall crash frequencies have been reduced, the crash reductions are most pronounced for motor vehicles, less pronounced for pedestrians, and mixed for bicyclists depending on the study and bicycle design treatments.
Why do roundabouts have such a good safety record?
1. Conflicts are reduced. Roundabouts have fewer conflict points in comparison to conventional intersections. The potential for hazardous conflicts, such as right angle and left turn headon crashes is eliminated with roundabout use. Singlelane approach roundabouts produce greater safety benefits than multilane approaches because of fewer potential conflicts between road users, and because pedestrian crossing distances are short.
2. Speeds are reduced and are more consistent. Low absolute speeds associated with roundabouts allow drivers more time to react to potential conflicts, also helping to improve the safety performance of roundabouts. Since most road users travel at similar speeds through roundabouts, i.e., have low relative speeds, crash severity can be reduced compared to some traditionally controlled intersections.
3. Pedestrians cross one direction of traffic at a time. Pedestrians need only cross one direction of traffic at a time at each approach as they traverse roundabouts, as compared with twoway and allway stopcontrolled intersections. The conflict locations between vehicles and pedestrians are generally not affected by the presence of a roundabout, although conflicting vehicles come from a more defined path at roundabouts (and thus pedestrians have fewer places to check for conflicting vehicles). In addition, the speeds of motorists entering and exiting a roundabout are reduced with good design. As with other crossings requiring acceptance of gaps, roundabouts still present visually impaired pedestrians with unique challenges.
That said, roundabouts are not always safer than other alternatives:
- For multilane roundabouts, bicycle safety at roundabouts has been found to be poorer than at other intersections unless separate bicycle or multiuse paths are provided around the outside of the roundabout.
- Pedestrians, especially visually impaired or blind pedestrians, can have difficulty when trying to judge gaps in traffic across entries or exits with more than one lane.
Excerpted from: Federal Highway Administration, Roundabouts: An Informational Guide, Report No. FHWARD00067, June 2000.
All content contained within these materials is the intellectual property of Maryland State Highway Administration.
© 2000 Maryland State Highway Administration.
Last modified: Tuesday July 9, 2000.