Drivers cautious on new 'diverging diamond' at Route 59 and I-88

  • Drivers are routed to the opposite side of the overpass on Route 59 at I-88 in the new diverging diamond interchange, designed to eliminate left turns in front of oncoming traffic, that opened Monday.

      Drivers are routed to the opposite side of the overpass on Route 59 at I-88 in the new diverging diamond interchange, designed to eliminate left turns in front of oncoming traffic, that opened Monday. Scott Sanders | Staff Photographer

  • Traffic began moving Monday through the new diverging diamond interchange at Route 59 and I-88 in Naperville.

      Traffic began moving Monday through the new diverging diamond interchange at Route 59 and I-88 in Naperville. Scott Sanders | Staff Photographer

  • Diverging Diamond

    Graphic: Diverging Diamond (click image to open)

 
 
Updated 9/21/2015 7:38 PM

Talk about a learning curve.

Naperville's diverging diamond interchange at Route 59 and the Reagan Memorial Tollway (I-88) went live Monday with 182,000 cars and trucks as guinea pigs in the altered reality where driving on the left is all right.

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Unlike traditional cloverleafs, the diamond design briefly shifts traffic into left 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.

"Am I doing this right?" one Daily Herald reporter wondered while test driving the new route. There was bemusement on the faces of some other drivers, but Illinois Department of Transportation spokesman Guy Tridgell reported no major problems Monday afternoon.

"We have observed folks maybe driving a little tentatively, a little slowly, perhaps because they're curious, but everything is going according to plan," Tridgell said.

Here's a snapshot of traffic at the diverging diamond.

• At 9:26 a.m., drivers exiting westbound I-88 to head south on Route 59 waited briefly at a light, then flowed smoothly onto lanes on the left side of the road. Despite the unconventional approach, traffic moved briskly and eased onto the right lanes by 9:28 a.m.

                                                                                                                                                                                                                       
 

• Drivers heading from northbound Route 59 onto westbound I-88 at 9:32 a.m. stopped at a light, then continued on the left side of the road. Westbound tollway traffic streamed easily onto an entrance ramp from a dedicated lane by 9:33 a.m.; other vehicles were shifted onto the right side of Route 59.

• At 12:45 p.m., a few drivers on southbound Route 59 seemed surprised by the new exit lane leading to eastbound I-88. Some abruptly merged and others moved slowly as if looking for road signs to tell them where their lane was headed.

• Around 2:30 p.m. on southbound Route 59, several drivers were observed peering around for the ramp leading to I-88 east.

• At 5:38 p.m. drivers were backed up on Diehl Road before Route 59. But once on Route 59, traffic moved relatively swiftly, merging onto the eastbound I-88 by 5:41 p.m.

The diverging diamond is designed to improve safety by eliminating left turns and uses less land than cloverleafs, a necessity in tight spots such as I-88 and Route 59.

                                                                                                                                                                                                                       
 

A similar interchange will be completed at the Jane Addams Tollway (I-90) and Elmhurst Road near Des Plaines in 2016.

The Illinois Department of Transportation opened another diamond interchange at I-57 and Route 13 this summer in Marion, in southern Illinois.

IDOT officials hope to reduce crashes involving left-hand turns at the location.

When the atypical 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.

The new interchange is part of the ongoing rebuilding and widening of Route 59 in Naperville and Aurora that's been tying up local traffic since 2013. The entire project will cost $90 million.

• Daily Herald staff writers Jessica Cilella, Katlyn Smith and Marie Wilson contributed to this report.

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