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Merging Guidelines

When a lane is closed for construction motorists may be instructed to use a technique called the Zipper Merge. A Zipper Merge occurs when motorists use both lanes of traffic until reaching the defined merge area, then take turns merging in "zipper" fashion into the open lane. Vehicles in the merging lane must signal, and drivers in the through lane must each let one vehicle merge. It is important to note this makes the traffic flow more quickly and efficiently for drivers in both lanes.  

Zipper merge diagram

The Zipper Merge is used when lane closures are required on longer, high traffic roads like Circle Drive.

There are number of benefits of a Zipper Merge: 

  • Reduces differences in speeds between two lanes 
  • Reduces the overall length of traffic backup 
  • Reduces congestion on freeway interchanges 
  • Creates a sense of fairness and equity that all lanes are moving at the same rate

 

 

 

Frequently Asked Questions

What is a Zipper Merger?
When a lane is closed in a construction zone, a Zipper Merge occurs when motorists use both lanes of traffic until reaching the defined merge area, and then alternate in zipper fashion into the open lane.

How is it different from a regular merge?
When most drivers see the first “lane closed ahead” sign in a work zone, they 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.

With the Zipper Merge, as you see the “lane closed ahead” sign and traffic backing up, stay in your current lane up to the point of merge. Then take turns with other drivers to safely and smoothly ease into the remaining lane. Don't worry about being “polite”. Drivers in the through lane must take turns merging.

It’s important to note that this makes the traffic flow more quickly and efficiently for drivers in both lanes. The key is to merge as late as possible.

So, I'm supposed to merge late?
Yes! As you see the “lane closed ahead” sign and traffic backing up, stay in your current lane up to the point of merge. Then take turns with other drivers to safely and smoothly ease into the remaining lane. Don't worry about being “polite”. When traffic is heavy and slow, it is much safer for drivers to remain in their current lane until the point where traffic can orderly take turns merging.  Vehicles in the merging lane must signal and drivers in the through lane must each let one vehicle merge.