Few things spark more tension on the road than a lane closing ahead. What appears to be a simple merge turns into one of the most debated (and misunderstood) traffic behaviors out there: the zipper merge.
While designed to improve the flow of traffic and reduce congestion, it often frustrates drivers who view it as “cutting the line.”
Brian Butterworth, director of driver training at AAA Northeast, explains how drivers can better understand when zipper merging applies, and how to use it safely to avoid unnecessary road rage.
What is a Zipper Merge?
A zipper merge is a lane management technique used in heavy or slow-moving traffic, in which drivers in both lanes take turns merging at a lane-reduction point. Instead of merging early, vehicles continue using both lanes fully and alternate like the teeth of a zipper at the merge point.
Car Maintenance for All Seasons
Is Zipper Merge a Law? The Biggest Misconceptions
The merge pattern is considered a recommended best practice rather than a formal law in most jurisdictions. Drivers are encouraged to follow it when conditions are congested, but it is not typically enforced as a legal requirement.
Misunderstandings around zipper merging often lead to unsafe behavior and frustration, according to Butterworth.
“Some common misconceptions are that the zipper merge is cutting in line or causes congestion, when in fact it uses more available road space and can help to reduce congestion,” Butterworth said. “Zipper merges require cooperation, and failing to do so may cause some drivers to rush ahead, only to slam on their brakes when they get to the end of the line.”
How to Zipper Merge
Proper zipper merging most relies on predictable, cooperative driving behavior.
“Cooperation, consistency, and signaling. Drivers in both lanes should work with each other to keep traffic moving by taking turns. Drive consistently — don’t speed up or slam on your brakes. Lastly, use your turn signal when merging at the end of your lane. When everyone uses the zipper method, no one is jumping ahead of their place in line.”
AAA’s Driver Education Approach
AAA teaches drivers to understand when zipper merging is appropriate and how to apply it correctly, depending on traffic conditions.
“It comes down to understanding when the zipper merge is appropriate,” Butterworth said. “When traffic is slow-moving or congested, the zipper merge uses the most available road space and helps keep traffic moving more evenly. When traffic is free-flowing, it’s better to merge early, when safe to do so, rather than waiting until the last moment to change lanes.”
Zipper merging works best when drivers understand both the strategy and the etiquette behind it. While not always legally required, it is a safer and more efficient way to manage congestion as lanes close or merge.
If you or someone you know is ready to learn how to drive, sign up for AAA Driving School, available in Massachusetts and Rhode Island.
Does merging stress you out? Tell us how you feel about the zipper merge in the comments below!
Last updated on August 7, 2026 by AAA Staff
Zach Laks is a freelance travel writer and editor who loves cruises, theme parks and resorts. His work has been featured in the New York Times, The Points Guy, Lonely Planet, Condé Nast Traveler, Travel + Leisure, Departures, CNN, Frommer’s and Fodor’s. @zachlaks
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13 Thoughts on “What Is a Zipper Merge?”
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I never heard of this technique. Unfortunately, my experience has been that if I allow one car to go, several more believe it’s their turn to go ahead of me as well.
The article ignores the more difficult and (in my experience) more common case of losing one out of three or more lanes; in theory this could be done by multiple partial zippers but in practice that is far too complicated. Also, highway departments can be grossly incompetent about zipper merging; last week on I-79 in northwestern Pennsylvania there were several signs telling people not to merge, then a final one saying ~”merge now” a very short distance before one lane began to narrow dangerously — on a road where drivers could legally do 65 or 70. Zipper mergers don’t work at that speed.
I do not believe that there is anything intuitively obvious about the value of zipper merging, especially when one lane appears to be going through while the other one is vanishing; this is not analogous to a zipper, in which both sides are equal. This is not a matter of discourtesy, or lack of “common sense”; there is no reason for drivers to expect it to work.
It’s not immediate intuitive in the sense that, like nearly all driving skills and rules, you have to learn it. Almost nothing about driving is completely intuitive we simply take it for granted because we’ve been doing it for long enough. If drivers used both lanes and merged at the merge point it would work fine, drivers just need to learn the concept and why it’s effective, otherwise they just assume they have to merge early.
When I was growing up, it was known as alternate feed. Seem that most drivers will cooperate, but a few won’t, even though they don’t gain much, so better to just let them go – I’d rather have that driver in front of me, not behind me.
The most wondrous zipper merge I ever witnessed was rush hour traffic leaving a military base. It worked perfectly; nobody tried to break the pattern. It takes a certain mindset to understand the why and how.
Zipper merging works great I do it all the time just wish everyone else would get the message and not wait until the last second and cause more problems and confusion for everyone else
You’ve misunderstood the article: the whole point is that merging should happen at the last moment.
Correct- both lanes should be used by everyone to then take turns merging at the merge point. As long as lane is open it can and should be used, unless there is free-flowing traffic at which point it makes sense to merge early.
The concept of zipper merging is logical and easily understood. The problem is that it depends on common courtesy, a trait that sadly is less “common” than it should be. Far too many drivers are competitive or consider themselves too superior to allow others to get ahead of them.
I wish states could post zipper merging signs so people would understand how it works. It’s the only fair way for traffic to move in these situations. If people understood how this worked, polite drivers wouldn’t feel so guilty doing this. Sometimes I feel like they get in the main lane and then they do get aggravated at all the people taking the lane that doesn’t have any cars in it. If people just came up to a traffic situation that they knew this was happening, like a dropped lane, everybody would just pick a lane to go into because it wouldn’t matter and you both get to the end of it at the same time and then it would be one car from one lane and one from the other lane.
To bad there is always a healthy number of “entitled “drivers who will squeeze in and out of the smallest gaps in traffic in my state.
Your zipper merge article is interesting, but for someone unfamiliar with or confused by the practice, the article fell short. A clear description of how to zipper merge and several diagrams for those who learn visually would be appropriate.
I agree with you, Susan. I taught Adults (Business and Computer skills). If I had no idea what a zipper merge is (although I never knew its official name) and when to use it, I would have no idea what this article is talking about and when to use this merge. Clear examples of when this type of merge is needed should have been given and to explain clearly how to do this merge. I also agree not everyone merges as they should– alternating one car from each lane. I have also found car drivers switch lanes without signaling or speeding up to get into the small available space in front of another driver–almost causing an accident–just because they are on a hurry (not because it was an actual necessity)!