The metro-east is experiencing a boom in construction of traffic roundabouts.

What's happening?

Traffic circles are planned to replace busy intersections in Belleville, O'Fallon, East St. Louis and likely other local communities in the future.

Currently, a pair of back-to-back roundabouts are under construction on Illinois 158 in Belleville near a complicated convergence of the highway with Illinois 13 and Illinois 15.

Illinois Department of Transportation engineer Richard Barbee said the Belleville roundabouts will make traffic flow much more smoothly in an area where three stoplights and four highway ramps clog the flow of cars and trucks.

"In our traffic models, it was indicated that roundabouts will improve the flow of traffic greatly," Barbee said. "Instead of sitting there waiting for a traffic light, drivers will be able to constantly enter the intersection, keeping the flow moving."

Barbee added that roundabouts are safer because, while traffic keeps moving, it flows in a circular pattern. That keeps cars from hitting squarely if they happen to collide. Glancing blows cause less severe injuries than head on or T-bone accidents.

What does it cost?

Belleville's two new roundabouts will cost about $4.7 million and will be paid for from IDOT's regular construction budget.

Barbee said the intersection that will be replaced has been a target for improvement for years.

O'Fallon's new roundabout, at the intersection of Milburn School and Simmons roads, isn't on a state highway. So City Administrator Walter Denton said O'Fallon had to find grant money to help pay for its construction.

Designed to improve traffic flow near O'Fallon Township High School District 203's freshman campus, the city's third roundabout will largely be funded by a state grant.

"We recently received a state Congestion Mitigation and Air Quality grant for the project and we are scheduled for funding in 2015," Denton said. "The total cost is estimated at $1,031,000 and the city's match is $199,000 to be paid from Motor Fuel Tax funds."

Denton said the two previously built roundabouts are doing so well that he could see the city adding even more.

"The reason for the new roundabout is to relieve traffic at two primary peak times: When school lets out at the Milburn Campus and evening rush hour," Denton said. "There are frequent backups that overload the current four-way stop. The new roundabouts at Simmons-Porter and Seven Hills-Old Vincennes were built for the same reason and are functioning quite well."

Barbee said roundabouts are generally cheaper to build than four-way intersections.

"It depends on the site," Barbee said. "But, since no turn lanes are necessary, it usually takes less right of way to build a roundabout than a four-way stop.

What's next?

Work on Belleville's two new roundabouts has already begun with traffic lanes being shifted to allow the southernmost circle to be poured. It is expected to be done by the end of this year with the second roundabout to the north completed by the fall of 2014, according to IDOT.

O'Fallon won't get the money for it's new roundabout until fiscal 2015. But Denton said that's a good thing because it will allow work to improve Milburn School Road that was delayed for about a year as construction crews waited for Ameren and AT&T to move utility lines to be completed first. He said that work and the roundabout job being done at the same time would create too many obstacles for motorists in the neighborhood.

Contact reporter Scott Wuerz at swuerz@bnd.com or call 618-239-2626.