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Roundabouts are (slowly!) eating up the suburbs

Hillsboro, Virginia recently added roundabouts at both ends of town to improve commuter flow from West Virginia to DC
Hillsboro, Virginia, recently added roundabouts at both ends of town to improve commuter flow from West Virginia to DC (Michael S. Williamson/The Washington Post)


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

Turns out the fine folks at the US Bureau of Transportation Statistics don’t track the country’s roundabouts, roundabouts, or roundabouts. In fact, no federal agency does. Instead, for a quarter of a century, that heavy responsibility has rested on the humble shoulders of the Rodegerdts, an engineer and talented amateur photographer and pianist in Portland, Ore.

In the late 1990s, the Federal Highway Administration drafted the unassuming but furtively 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 following the newfangled crossbreeds that were springing up like mushrooms 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 design designs. His count soon found its way onto the internet, where he still spends his free time combing through the submissions of a small army of amateur roundabout enthusiasts, scrutinizing new roundabouts and figuring out their construction dates from published reports and historical satellite imagery.

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).

Roundabouts are rare beasts compared to the hundreds of thousands of regular intersections that dot the American landscape and are dominated by stop signs and traffic lights. But unlike the motorists who often confuse and bother them, roundabouts get closer fast.

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

The modern roundabout relies on a geometric design that forces traffic to slow down and on a simple innovation that was born in 1960s Britain: the rule that those already inside the circle have the right of way. At traditional roundabouts, which still lurk in many East Coast cities, traffic moves faster and vehicles already on the roundabout often have to give way to newcomers.

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

“It’s very difficult to integrate roundabouts into our dense urban environment,” said Rodegerdts. “And so most roundabouts were introduced either in brand new subdivisions or as retrofits to existing – often suburban or rural – junctions.”

Why add a roundabout, you might be wondering. Because roundabouts offer impressive safety gains. In general, a roundabout will reduce fatal accidents by 90 percent and reduce all auto accident injuries by at least 75 percent, even when accommodating higher traffic volumes.

At a rural two-way stop, the gains can be even more dramatic. A roundabout can reduce all traffic accidents, both fatal and non-fatal, by almost 90 percent. After all, it’s almost impossible to blow through a roundabout at 60 mph and run over a minivan – an all-too-common occurrence at typical rural intersections.

“That’s the beauty of the roundabout,” Rodegerdts told us. “It’s the geometry. It’s the curves that do the work. And not just relying on a traffic control device to avoid a high-speed collision.”

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

City rankings, on the other hand, are almost pointlessly simple. However you split the data, the upscale Indianapolis suburb of Carmel ranks as the nation’s roundabout capital. And, much like the Rodegerdts’ database, Carmel’s network of roundabouts is largely the work of a visionary man — in this case, seven-year-old Republican mayor and niche famed roundabout booster Jim Brainard.

A qualified lawyer, Brainard had experience of roundabouts when he took up his post in 1996, having seen several in the UK. But these modern intersections made an impression, and when his constituents demanded a safer, more walkable city, he thought he had a solution.

Roundabouts were extremely rare in the United States at the time. As one of the highest-income and most educated cities in the country, Carmel was fertile ground for transportation innovation. Still, it took some effort and a weekend research stint at Purdue University to convince the skeptical urban engineer. (More than a hundred crossings later, Brainard said, what was once a 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 achieves the traffic-light holy grail of roundabout revolutionaries through sheer willpower — and a bit of carefully structured national debt.

Brainard’s stance 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 epochal terms and refers to European empires and monarchs when explaining the need to build an 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 together longer than any other mayor in the city’s history (a fun fact we borrowed from Indianapolis star columnist James Briggs). During this time, Brainard saw the city grow from 38,000 to over 100,000 residents.

As mayor, he built more than 140 roundabouts, reducing fatalities so drastically that the local fire department rarely uses their Jaws of Life extraction tools. But roundabouts are just one pillar in Brainard’s larger plan to build a dense, European-style city in central Indiana. To that end, he’s also added winding, leafy pathways 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 lynchpin in Brainard’s vision of a walkable inner city. That’s not only because they are often more pedestrian-friendly, but because they reduce pollution and allow designers to fit more traffic in a smaller space. On a key section of its major north-south thoroughfare, Carmel replaced five lanes with just two lanes and multiple roundabouts. Where these lanes used to be, green space and sidewalks have emerged, 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 when he leaves office next year, the city will be on track to only have one left. Ironically, as a nearby plaque notes, it is home to one of the first automatic traffic lights in the United States. And now, at least in Carmel, it will be the last.

“It’s right in the middle of the little downtown that’s always been there, and there’s buildings on all four corners, so that’s going to stay,” Brainard said, explaining that there just isn’t room for a roundabout at that point.

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

Why? Because, he said, “We’re going to build a roundabout at each end!”

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To get all questions, answers, and factoids in your inbox as soon as we post them, Sign up here. If your question inspires a column, we’ll send you an official Department of Data button and ID card. This week a button goes to our colleague Shira Ovide, who will be your Tech Friend for you sign up for their new newsletter. Shira’s questions about revolving doors got us thinking about other much-maligned circular things that are actually much more efficient. Another button goes to Rob DeRocker, the New York PR pro representing Carmel, who uttered the six most compelling words in English last year: “Let’s do a story about roundabouts.”

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