Can I move past traffic and get over at the end? What PA law says about a zipper merge
When you’re stuck in traffic and waiting to merge into a single lane, there’s perhaps nothing more irritating than cars zooming past you only to switch lanes directly at the merge point. Ironically, that might just be the right strategy.
This type of merge, known as a “zipper merge,” has become increasingly topical in Pennsylvania as construction projects continue across the commonwealth. Its use has been recommended by the Pennsylvania Department of Transportation at times, but is it the right strategy for you?
Here’s what you need to know about zipper merges in Pennsylvania.
How do zipper merges work?
If you’ve been driving for a long time, executing a zipper merge might feel foreign at first.
In the grand scheme of things, the concept is simple. This type of merge — also called a “late merge” — can occur when a lane is closed in a construction zone, prompting slow-moving traffic to funnel into a single lane. Motorists following a zipper merge are encouraged to use both lanes of traffic until reaching the merge point, where drivers then alternate into the open lane in a zipper-like fashion.
According to the PennDOT, a zipper merge can keep sluggish traffic flowing more consistently since both lanes remain in use for as long as possible. Instantaneous merging before a merge point generally serves to only slow traffic down.
Zipper merges represent the antithesis of the “early merge,” which is undoubtedly more common on the road. Through an early merge, drivers move as soon as possible to the lane that will continue through a construction zone. This type of behavior, while perhaps more convenient at face value, can lead to unexpected lane switches that can contribute to crashes, road rage and other undesired driving outcomes, traffic experts say.
According to a Montana Department of Transportation study, zipper merges can reduce the overall length of traffic backup by as much as 40%. MnDOT has recently led campaigns to promote the use of zipper merges in slow-moving traffic, though the technique’s use is not required by law.
Ultimately, zipper merges require the cooperation of many drivers on the road. In a 2019 TED Talk presentation, California Department of Transportation engineer Oliver Asis encouraged zipper merge use and noted traffic should reduce as more and more drivers buy in.
“You have to collaborate and work together with your fellow drivers for [traffic to reduce]. We all know sometimes in the real world this doesn’t happen,” Asis said. “But the next time you find yourself in a situation in which you have to merge, consider doing the zipper merge. It only helps reduce traffic, reduce your frustration levels and, on top of that, get to your destination more quickly.”
Are zipper merges required by law in Pennsylvania?
In short, no.
Zipper merges are not required by law in the Keystone State, though PennDOT has actively encouraged its use through promotional materials and social media posts. Drivers will not directly face penalties for choosing to merge into a single lane early, though it may result in more traffic congestion overall.
A few states directly recommend the technique’s use, including Arizona, Washington, Missouri, Kansas and North Carolina, according to reporting by The Hill, which also notes zipper merges are more commonly observed in Europe.
Driving safely in Pennsylvania
The PennDOT maintains a number of guides and brochures offering safety tips for Pennsylvania drivers, all available online at no cost.
Simply put, PennDOT encourages drivers to “Start SMART and Stay SMART” — a pair of acronyms offering straightforward roadway safety tips.
Start SMART
- S — Seat belt on, seat adjusted
- M — Mirrors adjusted and clear
- A — Air conditioning, heating and defrost panels on
- R — Radio and audio panel set
- T — Thoroughly check the area for traffic, people and objects
Stay SMART
- S — Watch your speed
- M — Frequently check your mirrors
- A — Avoid distractions
- R — Remember the rules of the road
- T — Give yourself enough time to reach your destination
Visit penndot.pa.gov/TravelInPA/Safety/TrafficSafetyAndDriverTopics/Pages/default.aspx to learn more about pedestrian safety, driving in the fall and winter, assisting young and old motorists, avoiding distracted driving and more. Other training materials include animations highlighting safe driving in several situations, including zipper merges.
The Pennsylvania Department of Transportation has not yet responded to a request for comment on zipper merges and their potential impacts on Pennsylvania roadways.
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