Ask a Trooper: The zipper merge has many traffic benefits

Published 4:51 pm Wednesday, March 18, 2020

Ask a Trooper by Troy Christianson

Troy Christianson


Question: Could you explain the zipper merge for merging into construction zones in Minnesota? I have tried using the zipper merge many times, and it seems that hardly anyone else on the road knows about how it is supposed to work. If another driver intentionally blocks a lane, isn’t that against the law?

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Answer: According to the Minnesota Department of Transportation, when a lane is closed in a construction zone, motorists should use both lanes of traffic until reaching the defined merge area, and then alternate in “zipper” fashion into the open lane.

Some drivers slow too quickly and move to the lane that will continue through the construction area. This driving behavior can lead to unexpected and dangerous lane switching, serious crashes and road rage.

It is suggested that when you see the “lane closed ahead” sign and traffic backing up, stay in your current lane up to the point of merging. At that point, take turns with other drivers to safely and smoothly ease into the remaining lane. When traffic is heavy and slow, it is much safer for motorists to remain in their current lane until the point where traffic can orderly take turns merging.

Studies show that the “zipper merge” works the best to keep traffic flowing, especially when there is a lot of traffic, by:

• Reducing differences in speeds between two lanes

• Reducing the overall length of traffic backup by as much as 40%

• Reducing congestion on freeway interchanges

• Creating a sense of fairness and equity that all lanes are moving at the same rate

The zipper merge also helps prevent road rage from drivers who intentionally go slow in the lane that is closing, and blocking other drivers from passing or getting through. That is against the law.  Lane blocking or impeding traffic fines are approximately $139, and the offense goes on your driving record. We are watching out for lane blockers in all situations.

You can avoid a ticket — and a crash — if you simply buckle up, drive at safe speeds, pay attention and always drive sober. Help us drive Minnesota toward zero deaths.

If you have any questions concerning traffic-related laws or issues in Minnesota, send your questions to Sgt. Troy Christianson, Minnesota State Patrol, at 2900 48th St. NW, Rochester, MN 55901-5848; or reach him at

Troy Christianson is a sergeant with the Minnesota State Patrol.