MnDOT Encouraging Drivers to Zipper Merge to Alleviate Backups

Ryan Juntti
Updated: July 02, 2019 07:57 PM

With the 4th of July right around the corner, thousands of drivers are going to be hitting the road in the coming days. Couple that with the fact it is construction season, and that can cause for some major backups.

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One of the areas in our region with construction is on Second Street in Duluth. The two lanes on Second Street reduce to one lane. 

In situations like this, MnDOT encourages drivers to use the zipper merge. It's a maneuver that MnDOT says reduces traffic backups by as much as 40 percent.

Traffic backing up for miles in construction zones is a sight that many of us are far too familiar with.

"Oh yeah. Some bad backups. I mean long backups," David Nilssen of Stone Lake, Wisconsin said when asked if he has seen an instance where he has seen heavy backups.

That is caused by drivers only using one lane or merging too early in areas that are going to be reducing to one lane.

"We know that the lane's closed. We can see that the lane is closed down there, and we want to immediately get into the open lane," said MnDOT Duluth Traffic Engineer Jim Miles.

But MnDOT is encouraging drivers to resist the urge to merge early, and do the zipper merge.

How it works is cars use both lanes up until the merge point when they then take turns driving into the open lane.

"It's more efficient, decreases the backups, it decreases the speed differentials," said Miles.

There are signs in place in most zipper merge situations that say "use both lanes during backups." As you approach the lane closure the signs tell you which lane is being closed, and then underneath that it says to "take turns at merge" and then to "begin merge." 

"I think if people follow it, yeah," Nilssen said when asked whether he thinks the zipper merge is a good solution.

And it's something Nilssen says made his trip back from San Antonio a lot easier.

"It was so nice coming up because two or three cars would go and then one would hold back, so you could get in and it worked great," said Nilssen.

Some drivers may think you should merge into the open lane as soon as possible.

"I think it's human nature, it's Minnesota nice," said Miles.

So Miles acknowledges it's a counterintuitive approach, yet he says it's the best way to make sure everyone gets to where they want to go.

"It is okay to use both lanes, so when that driver's going by you a little bit faster, but you're in both lanes, that's just the way it's supposed to work, so just be patient and if we all follow the rules so to speak, we'll get you through the work zone more efficiently, and safely," said Miles.

MnDOT encourages drivers to use the zipper merge anytime there are heavy backups, but they say the bottom line is to merge when it is safe to do so

One project using the zipper merge is the I-35 North Metro Split in Lino Lakes, Columbus, and Forest Lake. More information about that project is available here.


Ryan Juntti

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