Roundabouts (Safety benefits)

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

At traditional intersections with stop signs or traffic signals, some of the most common types of crashes are right-angle, left-turn, and head-on collisions. These types of collisions can be severe because vehicles may be traveling through the intersection at high speeds. With roundabouts, these types of potentially serious crashes are essentially eliminated because vehicles travel in the same direction and at low speeds.

The vehicle-to-vehicle conflicts that do occur at roundabouts generally involve a vehicle merging into the circular roadway. In the case of multilane roundabouts, conflicts may also occur as vehicles exit.

  • Studies of intersections in the United States converted from traffic signals or stop signs to roundabouts have found reductions in injury crashes of 72-80 percent and reductions in all crashes of 35-47 percent (Retting et al., 2001; Eisenman et al., 2004Rodegerdts et al., 2007).
  • A study of 19 higher-speed rural intersections (speed limits of 40 mph or higher) that originally had stop signs on the minor approaches and were converted to roundabouts found a 62 percent reduction in all crashes and an 85 percent reduction in injury crashes (Isebrands & Hallmark, 2012).
  • Studies of intersections in Europe and Australia that were converted to roundabouts have reported 25-87 percent reductions in injury crashes and 36-61 percent reductions in all crashes (Rodegerdts et al., 2010).
  • Based on the results of a 2004 study (Eisenman et al., 2004), it’s estimated that the conversion of 10 percent of the signalized intersections in the United States to roundabouts would have prevented approximately 51,000 crashes in 2018, including 231 fatal crashes and about 34,000 crashes involving injuries.

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Most U.S. studies have focused primarily on single-lane roundabouts. When included, two-lane roundabouts have been associated with smaller reductions in crashes compared with single-lane roundabouts (Retting et al., 2001;  Eisenman et al., 2004Rodegerdts et al., 2007) or with increases in crashes (Isebrands & Hallmark, 2012Wang & Cicchino, 2022).

A 2019 IIHS study, however, showed that the safety of two-lane roundabouts improves over time, as drivers become more familiar with them (Hu & Cicchino, 2019). The researchers looked at roundabouts built in Washington state between 2009 and 2015. They found that crashes at two-lane roundabouts decreased an average of 9 percent a year. At the same time, the odds that a crash at a two-lane roundabout involved an evident or incapacitating injury decreased by nearly one-third annually.

In addition to having fewer serious conflicts between vehicles than traditional intersections, roundabouts are generally safer for pedestrians as well. In a roundabout, pedestrians walk on sidewalks around the perimeter of the circular roadway. If they need to cross the roadway, they cross only one direction of traffic at a time. In addition, crossing distances are relatively short, and vehicle speeds tend to be low.

Studies in Europe indicate that, on average, converting conventional intersections to roundabouts can reduce pedestrian crashes by about 75 percent (Brilon et al., 1993Schoon & van Minnen, 1994). Single-lane roundabouts, in particular, have been reported to involve substantially lower pedestrian crash rates than comparable intersections with traffic signals (Brude & Larsson, 2000).

Crossing at multi-lane roundabouts can be more difficult for pedestrians than crossing at single-lane roundabouts. A study found that motorists failed to yield to pedestrians 2-3 times more at multi-lane roundabouts than at single-lane roundabouts (Rodegerdts et al., 2007). Another study found that drivers exiting a roundabout were less likely to yield to pedestrians than drivers entering a roundabout (Hourdos et al., 2012).

Reprinted with permission from the Insurance Institute for Highway Safety. Please visit here for the original article.

Full Article
Roundabouts defined
Safety benefits 
Safety challenges
Traffic flow benefits
Public opinion
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