Roundabouts (Safety challenges)

Insurance Institute for Highway Safety, Arlington, Virginia USA, reprinted with permission.

Despite the demonstrated safety benefits of roundabouts, some crashes still occur. An IIHS study of crashes at 38 roundabouts in Maryland found that four crash types — run-off-road, rear-end, sideswipe, and entering-circulating — accounted for almost all crashes (Mandavilli et el., 2009). Another common crash type involved a vehicle colliding with the central island. These crashes, which often involved unsafe speeds, accounted for almost half of all single-vehicle run-off-road crashes. Some drivers may not have seen the roundabout in time to slow down sufficiently.

A review of crashes at 39 roundabouts in the United States found that entering-circulating, exiting-circulating and rear-end collisions were the most common crash types (Rodegerdts et al., 2007). A large majority of crashes at the single-lane roundabouts were entering-circulating crashes. At multi-lane roundabouts, the majority of crashes were exiting-circulating.

A review of fatal crashes at roundabouts in the United States and injury crashes at roundabouts in Washington and Wisconsin found that motorcycle crashes, fixed object crashes, and crashes involving impaired driving were overrepresented (Schroeder et al., 2015).

>>Continue reading ...

Design features that encourage drivers to slow down are the key to optimizing roundabout safety.

Signs — including speed limits posted well in advance of roundabouts and larger "roundabout ahead" and yield signs — pavement markings and lighting help make sure drivers know they are approaching a roundabout and therefore need to slow down.

Center island landscaping can promote slower speeds and focus drivers' attention on the roadway close to them by limiting their through vision.

Islands separating the approach and exit lanes, known as splitter islands, should extend far enough from the roundabout to provide pedestrian refuge and to delineate the roundabout.

Other design features such as adequate curvature of approach roads far enough in advance of roundabouts and the alignment of approaching roads with the center island also may aid in reducing speeds.

Multilane roundabouts are more challenging. A study of a pair of two-lane roundabouts near Bellingham, Washington, found that confusion about some aspects of navigating the roundabouts persisted one year after the construction ended (Hu et al., 2014). More than 40 percent of drivers said it wasn't clear from signs and pavement markings what speed to drive, which lane has the right of way when exiting or that they shouldn't drive next to large trucks in the roundabouts.

At multilane roundabouts, signs and pavement marking should remind drivers of the correct yielding patterns and help them choose the appropriate lanes. At two-lane roundabouts, for example, signs need to convey clearly that entering traffic must yield to both lanes of traffic.

The photos below show sample signs and pavement markings used at roundabouts.

No Comments Yet.

Leave a comment