The rise of the roundabout and which state has the most

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

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

It turns out the fine folks at the U.S. Bureau of Transportation Statistics don’t track the nation’s roundabouts, rotaries or traffic circles. Indeed, no federal agency does. Instead, that weighty responsibility has, for a quarter of a century, fallen on the unassuming 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 hilarious Rodegerdts to write the book on roundabouts. The result was “Roundabouts: An Informational Guide.” In the course of his research, Rodegerdts was surprised to discover that nobody was keeping track of the newfangled intersections mushrooming across 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 online, where he still spends his spare time combing through submissions from a small army of amateur roundabout enthusiasts, verifying new roundabouts and sussing out their construction dates using published reports and historical satellite photography.

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

Compared with the hundreds of thousands of normal intersections peppering the American landscape, ruled by stop signs and traffic lights, roundabouts are rare beasts. But unlike the drivers they frequently confuse and bedevil, roundabouts are coming on fast.

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

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

In the United States, the earliest roundabouts often were constructed in bigger cities. In general, our analysis shows, they’re most likely to be built in well-educated, high-income towns. These days, the fastest growth is in suburbs and rural areas.

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

Why add a roundabout, you might ask. Because roundabouts offer impressive safety gains. In general, a roundabout will drive down fatal crashes by 90 percent and cut all car-crash injuries by at least 75 percent, even while accommodating a higher volume of cars.

At a rural two-way stop, the gains can be even more dramatic. A roundabout can slash all traffic injuries, both fatal and nonfatal, by almost 90 percent. After all, it’s almost impossible to blow through a roundabout at 60 miles an hour and T-bone a minivan — an all-too-common occurrence in typical rural intersections.

“That’s the beauty of the roundabout,” 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 sole thing keeping you from colliding at high speed.”

So which state is the roundaboutiest? Florida boasts the most roundabouts, but it also has the third-largest population in the nation. Nebraska has the most roundabouts per person, but they’re spread across one of the sparsest (and often most scenic) road networks in the country. Per mile of road, Maryland actually emerges as the roundabout champion.

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

A lawyer by training, Brainard’s experience with roundabouts when he took office in 1996 consisted of having seen several in the United Kingdom. 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 vanishingly rare in the United States back then. As one of the highest-income, most educated cities in the country, Carmel was fertile ground for the traffic innovation. Still, it took some effort and a weekend research trip to Purdue University to convince the city’s engineer, who was skeptical. (More than a hundred intersections later, Brainard said, that onetime 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 moved cautiously, but Brainard is attaining the traffic-signal-free holy grail of the roundabout revolutionaries through sheer force of will — and a bit of carefully structured public debt.

Brainard’s attitude is that if Paris can build a world-class, roundabout-infused urban area on a flat piece of unspectacular but fertile ground, then so can Carmel (pronounced CAR-mull). He’s careful but bold, speaking of his goals in epochal terms, referring to European empires and monarchs as he explains the need to build infrastructure to 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, as White flight began to swell it and other suburbs. Brainard has now served longer than every 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 residents to more than 100,000.

As mayor, he has built 140-plus roundabouts, slashing traffic fatalities so dramatically that the local fire department rarely uses its Jaws of Life extraction tools anymore. But roundabouts are just one pillar in the grander Brainard plan to build a dense, European-style city in central Indiana. To that end, he’s also added winding, leafy trails and a glittering concert hall that hosts everything from Carmel Symphony Orchestra performances to Michael Bolton holiday specials.

Why does the Midwest love orchestras so much?

The roundabouts are a linchpin in Brainard’s vision of a walkable downtown. That’s not just because they’re often friendlier to pedestrians, but because they can reduce pollution and allow designers to fit more traffic in a smaller space. In a key stretch of its main north-south drag, Carmel replaced five lanes of traffic with just two lanes and multiple roundabouts. Green space and sidewalks have sprouted where those lanes used to be, and total traffic flow on the road has actually increased.

In all of Carmel, just nine regular traffic signals remain, Brainard said. And by the time he leaves office next year, the city will be on track to have just one. Ironically, as a nearby plaque notes, it’s 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 there forever, and there’s buildings on all four corners, so that’s the one that’ll stay,” Brainard said, explaining that there’s just no room for a roundabout in that spot.

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

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

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To get every question, answer and factoid in your inbox as soon as we publish, sign up here. If your question inspires a column, we’ll send an official Department of Data 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 her new newsletter. Shira’s questions about revolving doors got us thinking about other much-maligned circular things that are actually way more efficient. 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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