Roundabouts eat up (slowly!) the suburbs

Hillsboro, Virginia, recently added roundabouts at both ends of the city to improve the flow of commuters en route from West Virginia to DC
Hillsboro, Virginia, recently added roundabouts at both ends of the city to improve the flow of commuters going from West Virginia to DC (Michael S. Williamson/The Washington Post)


A silent roundabout revolution is sweeping through America’s suburbs. And it may have continued, unmeasured and unnoticed, if not for Lee Rodegerdts.

As it turns out, the fine folks at the U.S. Bureau of Transportation Statistics don’t track the country’s roundabouts, roundabouts, or roundabouts. Indeed, no federal agency does. Instead, for a quarter of a century that heavy responsibility has rested on the humble shoulders of Rodegerdts, an engineer and talented amateur photographer and pianist in Portland, Oregon.

In the late 1990s, the Federal Highway Administration drafted the humble but secretly hilarious Rodegerdts to write the book on roundabouts. The result was “Roundabouts: an informative guide.” During his research, Rodegerdts was surprised to discover that no one was keeping track of the newfangled intersections that are popping up like mushrooms in the country.


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So he started counting. And he kept counting, through another edition of the guide, through dozens of roundabout conferences and confabs, through roundabout research projects, and through endless actual roundabout construction designs. His count soon migrated onlinewhere he still spends his spare time scouring submissions from a small army of amateur roundabout enthusiasts, verifying new roundabouts and figuring out their construction dates using published reports and historic satellite photography.

When Rodegerdts started, he counted about 300 roundabouts nationwide. Only 25 years later, he counts about 9,000. And that doesn’t include more than 160 roundabouts or more than 700 traffic calming circles (which are very different from roundabouts).

Compared to the hundreds of thousands of normal intersections that dot the American landscape, ruled by stop signs and traffic lights, roundabouts are rare beasts. But unlike the drivers who often confuse and trick them, roundabouts come up quickly.

“People doubted we could keep up,” Rodegerdts said. “But so far I think we’ve done that.”

The modern roundabout is based on a geometric design that forces traffic to slow down, plus a simple innovation that originated in 1960s Britain: the rule that people already in the circle have the right of way. In traditional roundabouts and roundabouts, which still lurk in many East Coast cities, traffic moves faster and vehicles already in the roundabout often have to give way to newcomers.

In the United States, the first roundabouts were often built in larger cities. Overall, our analysis shows that they are likely to be built in well-educated, high-income cities. Today, the fastest growth is in suburbs and rural areas.

“It is very difficult to fit roundabouts into our densely populated urban environment,” says Rodegerdts. “And so most roundabouts have been put in place, either in brand new subdivisions or retrofits of existing — often suburban or rural — intersections.”

Why add a roundabout you may ask. Because roundabouts offer impressive safety gains. In general, a roundabout will reduce fatalities by 90 percent and reduce injuries in car crashes by at least 75 percent, even if more cars can be transported.

With a two-way stop in rural areas, the gains can be even more dramatic. A roundabout can reduce all road injuries, both fatal and non-fatal, by almost 90 percent. After all, it’s nearly impossible to blast through a roundabout at 60 miles per hour and T-bone a minibus—an all-too-common occurrence at typical rural intersections.

“That’s the beauty of the roundabout,” says Rodegerdts. “It’s the geometry. It’s the curves that do the work. And don’t rely on a traffic controller as the only thing stopping you from colliding at high speed.”

So which state is the most roundabout? Florida has the most roundabouts, but it also has the third largest population in the country. Nebraska has the most roundabouts per person, but they’re spread across some of the thinnest (and often most scenic) road networks in the country. Mile by mile, Maryland actually emerges as the roundabout champ.

City rankings, on the other hand, are almost pointlessly simple. Almost any way you slice the data, the exclusive Indianapolis suburb of Carmel ranks as the roundabout capital of the country. And, like the Rodegerdts’ database, the Carmel network of roundabouts is largely the work of one visionary man – in this case the Republican mayor and niche famous roundabout booster Jim Brainard.

A lawyer by training, Brainard’s experience with roundabouts when he took up office in 1996 was that he had seen several around the UK. But those modern intersections made an impression, and when his constituents demanded a safer, more walkable city, he thought he had a solution.

Roundabouts were a rarity in the United States at the time. As one of the most educated cities in the highest-income country, Carmel was a fertile ground for transportation innovation. Still, it took some effort and a weekend research trip to Purdue University to convince the city engineer, who was skeptical. (More than a hundred intersections later, Brainard said, that former skeptic has become a sought-after leader in roundabout engineering and a commanding general in the roundabout revolution.)

Most roundabout-curious cities and counties have proceeded with caution, but Brainard achieves the traffic light-free holy grail of the roundabout revolutionaries through sheer force of will—and a little carefully structured government debt.

Brainard’s attitude is that if Paris can build a world-class urban area with roundabouts on a flat piece of unspectacular but fertile ground, so can Carmel (pronounced CAR-mull). Cautious but bold, he speaks of his goals in seminal terms, referencing European empires and monarchs while explaining the need to build infrastructure that will last for the next thousand years.

And monarch is almost a fitting job description for Brainard at this point. Carmel became a city in 1976, when White Flight began to swell it and other suburbs. Brainard has now served longer than any other mayor 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 inhabitants to more than 100,000.

As mayor, he built more than 140 roundabouts, reducing traffic deaths so dramatically that the local fire department rarely uses Jaws of Life extraction tools. But roundabouts are just one pillar in the larger Brainard plan to build a densely populated European-style city in central Indiana. He has also been added to that winding, leafy paths and a beautiful concert hall showcasing everything from performances by the Carmel Symphony Orchestra to Michael Bolton holiday specials.

Why does the Midwest love orchestras so much?

The roundabouts are a pivot in Brainard’s vision of a walkable centre. That’s not easy because they are often friendlier to pedestrians, but because they can reduce pollution and allow designers to fit more traffic into a smaller space. On an important stretch of the main north-south highway, Carmel replaced five lanes with just two lanes and multiple roundabouts. Green space and sidewalks have sprouted up where those lanes used to be, and overall traffic flow on the road has actually increased.

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

“It’s in the middle of the little downtown that was always there, and there are buildings on all four corners, so that’s the one that’s going to stay,” Brainard said, explaining that there’s just no room for a roundabout on that place.

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

Why? Because, he said, “We built a roundabout at each end!”

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To get every question, answer and factoid in your inbox as soon as we publish, Register here. If your question inspires a column, we’ll send an official Department of Data button and ID card. This week, one button will go to our colleague Shira Ovide, who will become your Tech Friend if you do sign up for her new newsletter. Shira’s questions about revolving doors make us think about other much-maligned circular things that are actually much more efficient. Another button goes to Rob DeRocker, the New York public relations professional representing Carmel who uttered the six most irresistible words in the English language last year: “Let’s do a story about roundabouts.”

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