News Release

ST. PAUL, Minn.— The Minnesota Department of Transportation’s new Dynamic Late Merge System instructs drivers to take turns when entering a single lane closure situation to help reduce delay time in work zones.

This “take-turn” strategy often referred to as the “zipper” approach is used when traffic is congested. In this instance, drivers should use both lanes all the way to the designated merge point and then take turns merging.

“Drivers can help reduce frustration in work zones if they follow the directions on the signs; otherwise, the system won’t be as effective,” said William Servatius, Mn/DOT’s workzone safety specialist. “In some back-up situations, the signs have instructed drivers to use both lanes up until the merge point, but we’ve seen drivers merge too early – probably in fear that they won’t be let in by other drivers.”

Research has shown that 15 percent of drivers admitted to straddling lanes in order to block late mergers in construction zones.

“Many people think it is unfair for them to be waiting in traffic and another driver gets to merge before them,” said Servatius. “We’re hoping that this aggressive driver behavior will decrease if they see the signs instructing drivers to do so.”

The fully automated system consists of using remote traffic microwave sensors and a Doppler radar giving drivers instructions via changeable message signs on when to merge and how to merge according to the current state of traffic. Mn/DOT tested the system during last year’s construction season.

“So far this system has proven to help traffic flow by decreasing queue lengths as much as 35 percent. It has also reduced lane-changing conflicts and sudden-stop crashes,” said Craig Mittelstadt, Office of Construction and Innovative Contracting. “However, it can only work properly if drivers comply with the messages.”

The Dynamic Late Merge System is being tested at the following locations:

• Highway 52 and Lafayette Road in St. Paul
• Interstate 35 south of the Twin Cities

Mn/DOT also says they are hoping motorists will use the zipper approach whether message signs are posted or not in any drop lane situations when traffic is congested.

“We appreciate motorists wanting to merge early so they can avoid unsafe merging maneuvers, and they should merge early under normal traffic speeds,” said Mittelstadt. “But when the roadway is congested, drivers should use both lanes all the way to the designated merge point and then take turns merging.”

Minnesota is one of the first states to use the Dynamic Late Merge System

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