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updated: 5/1/2014 6:46 PM

Tollway trying new shape at old interchange

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  • Photo Courtesy Missouri Department of TransportationMissouri is a diverging diamond interchange pioneer, building its third in 2010 on I-270.

    Photo Courtesy Missouri Department of TransportationMissouri is a diverging diamond interchange pioneer, building its third in 2010 on I-270.

  • Diverging diamond

    Graphic: Diverging diamond (click image to open)


Drivers tired of the same-old, same-old will be able to test out an unconventional interchange at the Jane Addams Tollway (I-90) and Elmhurst Road once it's completed in 2016.

The atypical design, called a diverging diamond interchange, was first introduced in the United States in 2009 in Missouri.

A diverging diamond interchange is intended to allow safer, smoother traffic flow on busy roads that intersect with highways. What will take some getting used to is that it briefly shifts traffic into opposite lanes using signals on bridges or underpasses so that vehicles can turn left onto the highway without facing oncoming cars. Then, traffic is routed back to the right side of the road.

Some drivers at an Illinois tollway open house Thursday in Elk Grove Village were intrigued and some were skeptical. The project is part of a major reconstruction and widening of I-90.

"I can't wait to see how that works," Elk Grove Village resident Don Swiet said, adding he feared traffic backups. "Why not a regular cloverleaf?"

Tollway officials said the project should move traffic more safely and efficiently.

"There will be free-flow movements onto all the ramps which reduces the amount of potential accidents that could happen," tollway senior project manager Hope Garrett said. "The traffic crosses over and travels in the opposite direction than (drivers) are currently used to and then crosses back so all the ramps can be accessed as a simple turn movement."

The Elmhurst Road and I-90 interchange was built in 1958 when much of the traffic flow centered on travel between Chicago and the suburbs. As a result, existing ramps only allow access to and from the east. Now with more diverse traffic patterns and suburb-to-suburb commuting, the interchange will be rebuilt to allow access to and from the west.

The Illinois Department of Transportation is working on two other diverging diamond interchange projects -- one at Route 59 and the Reagan Memorial Tollway (I-88) in Naperville and another on I-57 in downstate Marion.

When the counterintuitive design was introduced in Missouri, it sparked fears it would cause accidents and confuse drivers. But Missouri officials say it's working and has increased safety.

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