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Interstate 55 Improvement Project

Project Updates (updated 5/29)

  • One lane on southbound I-55 south of U.S. Route 61 closed on May 29 and will remain closed around-the-clock for 40 days.  During the southbound lane closure, concrete traffic barriers will be up and the open lane of traffic will only be 11 foot wide. 

  • Weekend lane closures in various locations of I-55 will be starting up again soon.  Details will be posted here as they become available. 
  • As a reminder, when there are lane closures, drivers should use the zipper merge.  We want you to fill up both lanes of traffic and then take turns merging just before the closure point.  This will actually make traffic flow better and decrease merging dangers.  By using both lanes, you reduce the speed difference between the two lanes and can reduce the length of backups by up to 50-percent.  Click here for more information on the zipper merge.


What is being done on Interstate 55?

MoDOT is rehabbing 21 bridges over northbound and southbound I-55 from Route Z near Pevely to I55MapPlattin Creek just south of Crystal City (approximately 8 miles).  In addition, I-55 from Route Z to the Ste. Genevieve County

line (approximately 16 miles) will be resurfaced.  Guardrail and sign improvements will also be made.

How will traffic be impacted during construction?

The work will require overnight and weekend lane closures along I-55 throughout the duration of the project.  In addition, there will be long term lane closures.  One lane of traffic will be kept open at all times, but traffic is expected to back up whenever there are lane closures.  Weekend lane closures on northbound I-55 will run from Friday afternoon to early Monday morning, while the southbound closures will run from Friday evening through Monday afternoon.

How can I get through the work zone safely?

MoDOT will use the zipper merge technique whenever there are lane closures.  Most motorists start to merge as soon as they see warning signs and learn which lane ahead is closed. When the highway is not heavily congested and traffic is able to move at the speed limit, it is best to merge early into the open lane.  However, in dense, slow moving traffic, the open lane fills quickly. Motorists are forced to slow in the closed lane and may become anxious to merge. When a driver in the closed lane can’t move into the open lane in time, the closed lane ends forcing the vehicle to suddenly stop. The vehicle must now join traffic from a dead stop. This driving behavior can lead to dangerous lane switching, inconsistent driving speeds that cause crashes, long back-ups and road rage.

Research shows these dangers decrease and traffic moves more smoothly when motorists use both lanes until reaching the defined merge area and then alternate merging every other vehicle in "zipper" fashion into the open lane.



Driving Tips for Merging:

Early Merge Zipper Merge
  • Light congestion and traffic can move at the speed limit – merge early.
  • Early Merge:  Drivers move out of the closed lane as early as possible.
  • Heavy congestion with slowed or stopped traffic – use both lanes and merge at the lane closure.
  • Zipper Merge: Drivers fill both lanes and take turns merging every other car at the point of the lane closure.
Early Merge Zipper Merge

By using two full lanes of traffic until the merge, you reduce the difference in speed between the two lanes. The length of backups is reduced 40-50 percent. When both lanes continue to move slowly, everyone is equally delayed, which reduces road rage.



Watch for Signs Like These:


DMS Message Board

DMS Message Board DMS Message Board

How else can I get around?

You can avoid the delays on I-55 by taking Route 61/67.

When will the work take place?

Work began in March 2017 and will continue through late 2018.

What is the estimated project cost?

The project was awarded to Magruder Paving, LLC for $14 million.

Who can I contact for more information?

Contact MoDOT Franklin/Jefferson County Area Engineer Judy Wagner at 314-453-5021 or by e-mail at Judy.Wagner@modot.mo.gov.

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