Adam Klawonn
The Arizona Republic
Arizona drivers can expect to face a new challenge: the European roundabout, which state transportation officials have approved as an alternative to traffic signals at 15 major interchanges.

In the traffic land of straight lines and signalized grid systems, they are signal-less circles where motorists merge and putter around without stopping.

Lou Murphy, 74, who lives in Mesa during the winter, was skeptical. She said a roundabout in her home city of Clearwater, Fla., confused and angered motorists.

"People down here (in Florida) drive like they do in Arizona, fast and furious, and you can't do that in a roundabout," she said.

But roundabouts are becoming the rule. Under a new state mandate, engineers and designers have been ordered to consider roundabouts, a cheaper alternative to normal interchanges, as an option for future projects.

There's no question public education will be needed, said Matt Burdick, an Arizona Department of Transportation spokesman.

The next edition of state driver's manuals will contain a section on using roundabouts.

"It's completely different as far as the driving culture," Burdick said. "We are used to driving straight and driving fast in our intersections."

Up to 31 roundabouts are being considered for traffic interchanges from Flagstaff to the Mexican border. Designs already are under way for six of the sites, Burdick said.

That includes the Interstate 17 interchange at Cordes Junction for Prescott-bound traffic.

Roundabouts have been proposed for Brown and McKellips roads along a planned future leg of Loop 202. Residents in northeast Mesa have been generally supportive of the idea.

The plans will go to the City Council on May 6. If approved, the roundabouts will be built in three years.

A citizen advisory board approved the plans unanimously Tuesday, but not without some debate.

Board member Chester Wilt expressed his apprehension, saying that sometimes even a straight road confuses him.
Extensive public education is needed, and there's little margin for engineering error, said Gene Russell, a retired Kansas State University professor specializing in roundabout-operations research.

"It's more an art than a science," he said. "They (designers) think, 'I'll take it out of the federal manual,' but it's easy to screw them up."

For details, see the state's only major public roundabout, at Interstate 17 and Happy Valley Road, said Steve Wilcox, an ADOT designer. The state is planning to alter it so cars can enter side by side at a steeper angle because there are too many fender-benders in the circle. Construction is planned for next year.

State officials are working with Barry Crown, an Englishman who is the world's premier roundabout consultant.
Russell cautioned that roundabouts should be taken on a case-by-case basis.

"Even I wouldn't say 'Put them everywhere,' " he said. "But it should be part of the process and in the toolbox of any traffic engineer."

Officials say roundabouts are an efficient cost-effective way to move large amounts of traffic safely through major interchanges.

They're cheaper than other intersections, which can require bridges, traffic signals and electricity to run the signals. Signals for one Mesa intersection cost about $100,000, in addition to an annual electricity cost of $1,560, said Dan Cleavenger, an assistant Mesa traffic engineer.

"They've converted me," he said. "I didn't have experience with roundabouts very much, but with graphics and simulations they've used, I'm absolutely willing to try this."

Officials cite a 2000 study from the Insurance Institute of Highway Safety, which looked at crashes and injury statistics at 24 intersections before and after roundabouts.

The study said roundabouts reduce overall crashes by 39 percent and injury-producing crashes by 76 percent. Fatal collisions dropped 90 percent, according to the study, largely because of low speeds.

Mesa's proposed roundabouts would have pedestrian crossings, clearly marked lanes and signs. Speeds would be kept under 25 mph; there would be no left-turn lanes.

Traffic coming into the roundabout would yield to the traffic already within it, a key difference between roundabouts and their ancestor, the ill-famed traffic circles or "rotaries" found back East.