Innovation: Missouri leads in use of French highway exit design

Kansas City StarDecember 4, 2009 

KANSAS CITY — The French are starting to influence our highways.

What was once a unique driving idea for Kansas City is spreading nationwide with an interchange design pioneered in France that has a distinctive European twist: driving on the left side of the road.

Hailed by Popular Science magazine as one of the top innovations of 2009, the design features a traffic signal that moves both directions of traffic to the opposite side of the road before crossing the freeway. That permits drivers to make left turns onto the highway without stopping at another red light.

Experts say Missouri has emerged as the nation’s leader in designing this “diverging diamond interchange.”

The first such interchange in the country opened in June on Interstate 44 in Springfield. Perhaps a dozen others are in the works across the country, including three in the Kansas City area.

The design was first proposed locally for Interstate 435 and Front Street, but that project was delayed until 2011 because it conflicted with the nearby Paseo Bridge project.

Now two more such projects are on the horizon: at Interstate 70 and Woods Chapel Road in Blue Springs and at Missouri 150 and Botts Road in south Kansas City.

The interchange is generally considered useful in areas where drivers have to make a number of left turns.

These interchanges cost less because they use up less land while handling traffic. They’re also believed to be safer because they reduce the number of points where vehicles might collide.

“The highway community is waking up to them,” said Stephen Dearing, a Michigan engineering consultant who has studied the novel design.

“They are not the silver bullet. But if you use them for the right reason in the right location, they’re going to really help address chronic congestion,” said Dearing, traffic engineering services manager for the consulting firm Orchard, Hiltz & McCliment.

Blue Springs is paying the $8.5 million bill for its interchange at I-70 and Woods Chapel. Construction is expected to begin in 2011 and be completed by the fall of 2013.

Right now, drivers going north on Woods Chapel Road get stuck waiting to turn left onto westbound I-70. With the new design, drivers will be able to make an uninterrupted left turn onto I-70 after moving to the left side of the road.

“It just sucks that traffic up. It’s like a vacuum. It’s a no-brainer,” said Oliver DeGrate, public works director for Blue Springs.

City officials acknowledged they were skeptical about the idea when it was first raised. But they believe the design has been vetted sufficiently by the federal government.

They also looked at the Springfield interchange at I-44 and Kansas Expressway. They believe drivers will be able to adjust to the new design.

“Why we haven’t been doing it for decades, I don’t know,” said Jeff Sell, the assistant public works director in Blue Springs.

Oregon, Florida, Utah and Maryland are among the other states looking at the design. Michigan considered the idea but dropped it because engineers weren’t quite comfortable with shifting drivers to the left side of the road.

“That would be a huge learning curve,” said Rob Morosi, spokesman for the Michigan Department of Transportation.

But the Federal Highway Administration got positive results when it ran simulations with drivers using the proposed Kansas City interchange at Front Street and I-435.

The agency used 74 drivers from the Washington, D.C., area, including 33 who were older than 65.

The study dismissed safety concerns that drivers would try to veer to the right even though they were supposed to steer to the left side of the roadway. “The simulation suggests that this concern is not warranted,” the study said.

Overall, the study found that properly designed diverging diamond interchanges would prove to be “considerably” safer than a conventional diamond interchange.

In Springfield, police reported only five minor crashes at the new interchange in the first two months after the intersection opened. At first, there was some confusion with drivers wanting to stay to the right, but overall, traffic has moved smoothly.

“It works pretty much flawlessly,” said Police Lt. Faye Barksdale. “We believe (traffic) has improved considerably.”

Federal highway officials believe that early successes in Missouri could lead to more such interchanges across the nation.

“Only a few exist in the world right now but, based on the success Missouri is having with them, they may become more common in the years ahead,” said Cathy St. Denis, spokeswoman for the Federal Highway Administration.

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