Traffic roundabouts making their way across the Treasure Valley | Idaho Statesman

Commonplace in Europe for more than a century, roundabouts re-emerged in the United States about 25 years ago. More than 3,000 roundabouts dot the nation today.

The Treasure Valley came round a little slowly, building its first roundabout in 2006. Now more than a dozen can be found across the Valley from Emmett to Nampa to Boise. And more are on the way.

Why roundabouts?

At a traffic light people speed up to make the light; at stop signs people intentionally or unintentionally run through them without stopping. With a roundabout, everyone has to slow down. And going slower means fewer mistakes.

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But going slower does not mean more congestion or longer delays because cars keep moving without stopping, which means traffic keeps flowing. And since cars aren’t idling at stop lights or stop signs, roundabouts also help reduce fuel consumption and emissions. Taxpayers, too, benefit because roundabouts have no traffic signal equipment to install, power and maintain.

So, roundabouts sound good on paper. But do drivers like them? Are they safer?

Initially drivers are leery of roundabouts, but once they get the hang of it, they become fans, according to a 2007 study by the Transportation Research Board of the National Academies in Washington, D.C. The research team interviewed 1,800 drivers in six cities and found that one-third of drivers favored roundabouts before construction. Shortly after construction that number rose to about 50 percent. By the time the roundabout had been in place in the community for a nearly a year, it received upward of 70 percent approval.

When compared to other types of intersections, roundabouts reduce fatalities by 90 percent, injuries by 76 percent and crashes by 35 percent, according to the Federal Highway Administration.

The main reason roundabouts are safer is they eliminate the most severe intersection accidents — T-bone and head-on collisions. A traditional intersection can have more than 30 points of conflict — places where diverging, merging or crossing vehicles can collide. Roundabouts have just eight and all involve vehicles moving in the same direction at a slower speed, not moving against each other at higher speeds.

The roundabout on Whitewater Boulevard — the new 30th Street extension from State Street to Fairview Avenue — is one of Boise’s newest roundabouts.

Since the roundabout opened in 2013, there have been no injury crashes and three noninjury crashes reported in the roundabout. Two of the crashes involved a single vehicle running off the road — one was a drunk driver, the other slid on an icy roadway. The third crash was one vehicle sideswiping another on an icy roadway, according to ACHD spokesperson Nicole Du Bois.

When the Treasure Valley’s first roundabout opened in 2006 at Happy Valley and Amity roads in Nampa, drivers experienced a bit of a learning curve. According to the city, there were 10 crashes per year the first two years after the roundabout opened; the number dropped to six in year three and then zero by the fourth year. Since then it has averaged about two crashes annually.

Survey says ...

An informal Idaho Statesman survey conducted via social media found four or five of about 50 respondents love the roundabouts.

“We use the ones on Happy Valley (Road in Nampa) every day. Makes commute much faster, less gas, easy to use,” wrote Tamara Peterson.

Several readers noted they have experienced roundabouts on the East Coast and in European and other countries, and are glad to see them making their way into Idaho.

Doug Shaver recently spent two weeks in Australia in a town of about 30,000 people that has no stoplights, only roundabouts. “Traffic moved smoothly and efficiently. But it would definitely take some getting used to,” Shaver wrote in a Facebook posting.

Not everywhere a roundabout

A 2012 ACHD analysis of 895 existing or future intersections determined 658 were not suitable for roundabouts due to traffic volume, right-of-way issues or corner, topographic or geographic constraints.

But that does not mean ACHD plans to put roundabouts in the 237 intersections deemed roundabout amenable.

ACHD considers roundabouts a “tool in the toolbox,” said Du Bois. “We’re looking at them on a case by case basis. … They are an option that perhaps we would not have considered five or 10 years ago.”

ACHD does have plans to build two roundabouts next year.

The confounding five-way traffic signal in Boise at 36th Street/Hill Road/Catalpa Drive by Hillside Junior High will be replaced with a dog-bone-shaped roundabout and downtown Kuna will get a roundabout at the three-way intersection of Linder Avenue/Main Street/3rd Street.