Published on February 23, 2021

Zipper Merges Keep Traffic Flowing

The first sign encouraging drivers to “Zipper Merge” has been installed on Ray Gibbon Drive. If you are travelling northbound near LeClair Way, you will see the new sign.

There is a great debate about the most effective way to change lanes when merging. Some argue the best method is moving over and getting in line as soon as possible. Others argue it is best to use all the real estate available and change lanes at the last moment.

If traffic is light, moving over as soon as you can makes the most sense and keeps traffic flowing. But, during moderate to heavy traffic, the answer is the zipper merge, which will keep traffic flowing and use each lane to its full extent.

Did you know? 
The zipper merge reduces the overall length of traffic backup by as much as 40 per cent.

What is a zipper merge?

When one lane of a two-lane road ends, possibly due to road design or if a lane is temporarily closed for construction, a zipper merge occurs into the other lane. This is when motorists use both lanes of traffic until reaching the defined merge area, and then alternate in "zipper" fashion into the open lane.

Why should I use a zipper merge opposed to an early merge?

If a driver sees the first “lane closed ahead” sign and decides to change lanes immediately, they will slow down too soon and move out of the lane that does not yet end. This driving behavior can lead to unexpected and dangerous lane switching, serious collisions, congestion, delay and driver frustrations.

Whereas the zipper merge maximizes the road space available, has shown to be more efficient and reduces the risk of accidents as other drivers anticipate their lane change.

Tips to perform a safe and effective zipper merge:

  • Drive consistently. Don’t rush ahead, only to slam on your brakes later.
  • When ready to move over, signal your intent and merge in an alternating fashion.
  • If there is no bottleneck and an early merge makes sense, feel free to do so.

When shouldn’t I use a zipper merge?

When traffic is moving at highway speeds and there are no backups (congestion) or in the event a lane is closed due to a collision or vehicle emergency (breakdown), do not zipper merge. In these instances, it is appropriate to reduce your speed as necessary, and move over sooner to the lane that will remain open. The priority is to merge when it is safe to do so.

AMA Zipper Merge Demonstration


Like this content?

To receive our weekly newsletter, Subscribe to City Highlights


Related Pages

Last edited: February 23, 2021