The Benefits of the Modern Roundabout

Image by Ken Sides, City of Clearwater
In 2007, the United States built its 1,000th roundabout. That same year, France built its 30,000th roundabout. Although countries around the world have taken the benefits of modern roundabouts to heart, this intersection solution has taken a little longer to grab hold in American municipalities. Nonetheless, as the benefits of this design become increasingly apparent (and needed), more and more intersections are following this circular model. So, what makes roundabouts so desireable?

Roundabouts Reduce Environmental Impacts

According to a study in Time Magazine, roundabouts cut hydrocarbon emissions at intersections by as much as 42%. By reducing idling, ten circular intersections in Virginia were found to save 200,000 gallons of gas each year. The “Gateway Roundabout” in Clearwater, Florida, replaced three signalized intersections and one stop-controlled intersection with a single two-lane traffic circle. Stop delays–and therefore emissions–were reduced by 68%. Likewise, similar interventions in Kansas were found to ease traffic delays by an average of 65%.

Roundabouts Are Safer by Design

Reduced risk when replacing intersections with roundabouts.Each year, over 30,000 individuals die in car crashes in the United States– and that doesn’t include the even greater number of annual crashes involving injuries to drivers and pedestrians. One solution to these high figures is the replacement of signalized and stop-controlled intersections with roundabouts.

The Federal Highway Administration (FHWA) and the Insurance Institute of Highway Safety found that replacing conventional intersections with roundabouts reduced overall collisions by 37%, collisions involving injuries by 75%, and collisions involving fatalities by 90%. Moreover, collisions with pedestrians were reduced by 40%.

Roundabouts Move More Cars

According to the FHWA, a single-lane roundabout can handle up to 2,500 vechilces per hour. It would take two travel lanes (and usually left and right turn lanes) in each direction to match that capacity. In other words, roundabouts handle more traffic with less pavement.


Overall, the benefits of these modern traffic circles are clear. While most traffic designers have caught on, it’s now up to local municipalities to allow for the conversion of conventional intersections.



1 reply
  1. Kunal
    Kunal says:

    I’m just going to toss in my tuppence here since I have lived in two ciites that share borders with the Mayor Brainard mentioned in the article cited. Roundabouts of the type built here (there are a few different kinds) have been excellent additions. He’s built them all over Carmel and they have even spread to intersections outside of his jurisdiction due to their obvious improvements (primarily in resolving congestion). Hamilton Co, where Carmel, Indiana is, is one of the nations fastest growing counties. It butts up against Marion Co, i.e., Indianapolis, the 12 or 13 largest city in the country. Most of Hamilton Co’s growth is in its two southern most ciites (Fishers and Carmel, both on the border between Marion and Hamilton Co) But fast growth in Hamilton Co and on Indianapolis’ northside is hampered by the inability to make the kinds of infrastructural developments needed to support that many more people. That is, these areas are already developed, so widening roads is time consuming, expensive, and very likely to upset the voters whose property you diminish either by taking it outright or by getting rid of sidewalks and easements. But changing an intersection from well an intersection to a roundabout is something than can easily be accomplished while improving the volume capacity of the existing roads. Opinions locally (I still live in Indianapolis, just further south) are obviously varied, but the consensus seems to be positive. They’re annoying going in And a few years ago when they first appeared there was a small learning curve. But now people are accustomed to using them and traffic moves very smoothly. It’ll be a few years before we see good data on accidents but I anticipate good results from those studies.

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