Roundabouts are (slowly!) eating the suburbs

Hillsboro, Va., recently added roundabouts on both ends of town to improve the flow of commuters heading from West Virginia to DC
Hillsboro, Va., recently added roundabouts on both ends of town to improve the flow of commuters heading from West Virginia to DC (Michael S. Williamson/The Washington Post)


A quiet carousel revolution is sweeping America’s suburbs. And it might have continued, unmeasured and unremarked, if not for Lee Rodegerdts.

It turns out the fine folks at the United States Bureau of Transportation Statistics don’t track the nation’s roundabouts, roundabouts or traffic circles. In fact, no federal agency does. Instead, that lonely responsibility has, for a quarter of a century, fallen on the sole shoulders of Rodegerdts, an engineer and talented amateur photographer and pianist in Portland, Ore.

In the late 1990s, the Federal Highway Administration drafted the modest but stealthily funny Rodegerdts to write the book on roundabouts. The result was “Roundabouts: An Information Guide.” During his research, Rodegerdts was surprised to find that no one was keeping track of the new fenced intersections that were springing up across the country.

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So he started counting. And counting, through another edition of the guide, through countless roundabout conferences and confabs, through roundabout research projects and endless roundabout construction designs. His count soon migrated online, where he still spends his spare time combing through submissions from a small army of amateur carousel enthusiasts, verifying new carousels and assigning their construction dates using published reports and historic satellite photography.

When Rodegerdts started, he counted about 300 carousels across the country. Just 25 years later, he counted around 9,000. And that doesn’t include 160-plus turns or 700-plus traffic calming circles (which are very different from roundabouts).

Compared to the hundreds of thousands of ordinary intersections across the American landscape, controlled by stop signs and traffic lights, roundabouts are rare animals. But unlike the drivers who often confuse them with the devil, roundabouts are catching on fast.

“People doubted we could keep up,” Rodegerdts told us. “But so far I think so.”

The modern roundabout relies on a geometric design that forces traffic to slow down, as well as a simple innovation born in Britain in the 1960s: the rule that people already in the circle get the right of way. In traditional roundabouts and traffic circles, which are still prevalent in many East Coast cities, traffic moves faster and vehicles already in the roundabout often have to yield to newcomers.

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In the United States, the earliest roundabouts were often built in large cities. In general, our analysis shows, they are more likely to be built in high-income, highly educated towns. These days, the fastest growth is in suburbs and rural areas.

“It’s very difficult to fit roundabouts into our dense urban environment,” said Rodegerdts. “And so most roundabouts are going in, either in brand new subdivisions or as retrofits to existing intersections — often suburban or rural.”

Why did you add a carousel, you might ask. Because roundabouts offer significant safety gains. In general, a roundabout will reduce fatal crashes by 90 percent and reduce all car accident injuries by at least 75 percent, even when serving a higher number of cars.

At a rural two-way stop, the gains can be even more dramatic. Roundabouts can reduce all traffic injuries, both fatal and non-fatal, by almost 90 percent. After all, it’s nearly impossible to blow through a roundabout at 60 miles per hour with a T-bone minivan – all too common in typical rural intersections.

“That’s the beauty of the carousel,” Rodegerdts told us. “It’s the geometry. It’s the curves that are doing the work. And not relying on a traffic control device as the only thing keeping you from a high-speed collision.”

So which state is the biggest carousel? Florida has the largest carousels, but it also has the third largest population in the nation. Nebraska has the most roundabouts per capita, but they are spread over one of the thinnest (and often most beautiful) road networks in the country. By the road mile, Maryland emerges as the champion of the carousel.

On the other hand, city rankings are almost too easy. Almost any way you slice the data, the exclusive Indianapolis suburb of Carmel is the carousel capital of the nation. And, like Rodegerdts database, Carmel’s carousel network is largely the work of one visionary man — in this case, seven-term Republican mayor and niche carousel booster Jim Brainard.

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As a lawyer by training, Brainard’s experience of vicissitudes when he took office in 1996 was that he had seen quite a few in the United Kingdom. But those modern intersections were implemented, and when his constituents demanded a safer and more walkable city, he thought he had a solution.

Carousels were rare in the United States at that time. As one of the highest income and most educated cities in the country, Carmel was fertile ground for traffic innovation. However, it took some effort and a weekend research trip to Purdue University to convince the skeptical city engineer. (More than a hundred intersections later, Brainard said, a one-time skeptic has become a popular leader in carousel engineering and a commanding general in the carousel revolution.)

Most roundabout-friendly cities and counties have moved cautiously, but Brainard is achieving the traffic-signless holy grail of roundabout revolutionaries through sheer force of will — and a bit of carefully structured public debt.

Brainard’s view is that if Paris can build a world-class metropolitan area, complete with a roundabout, on a flat, unsightly but fertile piece of land, so can Carmel (pronounced CAR-mull). He is cautious but bold, talking about his goals in terms of time, referring to European empires and monarchies as he explains the need to build an infrastructure that will last for thousands of years to come.

And monarch is almost a fitting job description for Brainard at this point. Carmel became a city in 1976, as White flight and other suburbs began to swell. Brainard has now served longer than all other mayors in the city’s history combined (a fun fact we borrowed from Indianapolis Star columnist James Briggs). In that time, Brainard saw the city grow from 38,000 residents to more than 100,000.

As mayor, he has built over 140 roundabouts, reducing traffic fatalities so much that the local fire department rarely uses his Jaws of Life extraction tools anymore. But the roundabouts are just one pillar in Brainard’s larger plan to build a compact, European-style city in central Indiana. To that end, it’s also added windy, leafy walkways and a glittering concert hall that hosts everything from performances by the Carmel Symphony Orchestra to Michael Bolton’s special holiday shows.

Why does the Midwest love orchestras so much?

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The roundabouts are a link in Brainard’s vision of a walkable center. Not only that because they are often more pedestrian-friendly, but because they can reduce pollution and allow designers to fit more traffic into a smaller space. In a central stretch of its main north-south drag, Carmel replaced five lanes of traffic with two lanes and multiple roundabouts. Green space and footpaths have grown where those lanes used to be, and the overall flow of traffic on the road has increased.

In all of Carmel, there are only nine regular traffic signals left, Brainard said. And by the time he leaves office next year, the city will be on track to have one. Ironically, as a nearby plaque notes, it is the site of one of the first automatic traffic lights in the United States. And now, at least in Carmel, it will be the last.

“It’s in the center of the small town that’s been there forever, and there are buildings on all four corners, so that’s the one that will stay,” Brainard said, explaining that there is no place for a roundabout in that location.

But “it is quite safe,” the mayor assured us. “You can’t drive fast through that area.”

Why? Because, he said, “We put a carousel at each of them!”

Hello! The Data Department would be nothing without your data-driven questions! We want to know what you are curious about. Which cities have the worst sprawl? Which countries export the most human hair? How many jobs did the Paycheck Protection Program really do save? Just ask!

To get all questions, answers and factoids in your inbox as soon as we publish, register here. If your question prompts a column, we’ll send an official Data Department button and ID card. This week, one button goes to our colleague Shira Ovide, who will be your Tech Friend if you sign up for their new newsletter. Shira’s questions about revolving doors got us thinking about other circular things that are far more insidious and actually far more effective. Another button goes to Rob DeRocker, the New York public relations professional who represents Carmel and who last year uttered the six most irresistible words in the English language: “Let’s do a story about roundabouts.”


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