Do Roundabouts Reduce Accidents?

American Drivers Adapting to European Traffic Circles

If you've driven in Europe or Latin America -- or even in any one of 30 U.S. states including California, Florida and Michigan -- chances are you've driven around a traffic circle or roundabout.

It's also likely that you considered yourself pretty lucky to survive the lane changes, the strange angle of entry and the rather biting question of who yields to whom. But you'd be wrong. Although roundabouts routinely give drivers fits -- as was famously depicted by the Griswold family in National Lampoon's European Vacation -- statistically they are much safer to negotiate than traditional traffic intersections.

Roundabouts are becoming increasingly common across the U.S. as states and municipalities seek new ways to increase traffic flow while reducing accidents and vehicle emissions. Roundabouts, which are smaller than traditional traffic circles, accomplish all three goals.

Pete Moraga at the Insurance Information Network told AOL Autos: "Roundabouts are big in Latin America and Europe but many people here don't know how to deal with them. The lane changes are a little confusing for people.

"But studies show these reduce common types of crashes like T-bones, that cause a lot of fatalities. With roundabouts, these crashes and rear-end crashes are reduced by the way traffic flows. We support [roundabouts] because we support anything that increases safety and reduces accidents."

While France has more than 20,000 roundabouts, the U.S. has built about 2,000 since the first was constructed in Nevada in 1990, but that number is growing rapidly. The city of Carmel, Indiana, is a case in point. In 2003 the city had 252 injury crashes on its 220 miles of roads. But by 2008 the expanding city had more than 395 miles of roadways while its number of accidents fell to 220. City officials directly attributed the drop in accidents to its roundabout-building initiative. More than two dozen roundabouts were built between 2003 and 2008, and by the end of 2010, the city had built more than 50.

Data from the Insurance Institute of Highway Safety back up the case for a wider adoption of roundabouts. A 2001 study reported that converting intersections from traffic signals or stop signs to roundabouts reduced injury crashes by 80 percent and all crashes by 40 percent. A similar study found a 75 percent decrease in injury crashes and a 37 percent decrease in total crashes at 35 intersections that were converted from traffic signals to roundabouts.

A study of 17 higher-speed rural intersections (40 mph and higher speed limits) found that the average injury crash rate per million entering vehicles was reduced by 84 percent and fatal crashes were eliminated when the intersections were converted to roundabouts. Studies of intersections in Europe and Australia that were converted to roundabouts have reported 41-61 percent reductions in injury crashes and 45-75 percent reductions in severe injury crashes.

Moraga cited a study that suggests that only about a third of the population supports the building of more roundabouts. But, after a roundabout has been built, about two-thirds to 70 percent of drivers in the community say they favor building more.

Moraga also cited one study that found roundabouts helped reduce vehicles' carbon monoxide emissions by 29 percent, and nitrous oxide emissions fell by 21 percent, the result of increased traffic flow and fewer vehicular stops and starts.

Russ Rader at the IIHS said: "Roundabouts are becoming more common. Many communities are beginning to recognize that roundabouts are the ideal solution to fix several problems – they not only improve safety, but they also reduce congestion and fuel consumption. Residents are sometimes skeptical at first, but once roundabouts are put into place and people see them in action, the former skeptics become believers.

"The big safety benefit is that roundabouts essentially eliminate the worst kinds of crashes such as T-bones and head-on impacts."

Because traffic moves in a single direction, roundabouts essentially eliminate the potential for dangerous crashes including right-angle, left-turn, and head-on collisions. They also reduce the likelihood of rear-end crashes because drivers don't speed up to make a yellow or green light or abruptly stop at a red light. The crashes that do occur at roundabouts generally are not severe, the IIHS said, because vehicles move more slowly than they do at conventional intersections.

Roundabouts also can benefit older drivers, as many accidents involving older drivers are the result of a driver failing to yield the right of way. An example would be a driver turning left into oncoming traffic at an intersection. This situation does not occur at a roundabout. Older drivers, Moraga said, really like roundabouts. A 2007 study in six communities where roundabouts replaced traditional intersections found that about two-thirds of drivers 65 and older approved of roundabouts.

Although some older traffic circles have traffic lights and stopping zones, modern roundabouts are smaller and therefore have a sharper approach to entry, resulting in drivers negotiating the roundabout at much lower speeds, so lights are not needed.

Obviously, 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. A common crash type at both single-lane and double-lane roundabouts involved vehicles colliding with the central island. These crashes, which often involved unsafe speeds or the driver not seeing the roundabout, accounted for almost half of all single-vehicle run-off-road crashes. There were no right-angle or head-on collisions.

Roundabouts may not be a candidate to replace every intersection, for example, where the topography does not allow it or there is unequal traffic flow in the intersecting streets. But where they are suitable, chances are you'll be seeing a few more of them in your future.

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