Zipper Merge

A zipper merge is used when a lane is closed. Drivers use both lanes until the merge point, then take turns entering the open lane one vehicle at a time.

Why it matters

Zip at the merge

Using both lanes keeps traffic moving and reduces delays, especially in busy conditions. Benefits include:

  • Balancing speeds between lanes
  • Shortens traffic backups, sometimes by up to 40 percent
  • Reduces stop-and-go driving
  • Creates a more orderly and predictable merge

How it compares to early merging

Merging too soon after a “lane closed ahead” sign can lead to long backups, sudden braking and unsafe lane changes.

A zipper merge keeps both lanes moving to the merge point, where drivers alternate in a steady, controlled way.

When to zipper merge

During, heavy, slow-moving traffic

Stay in your lane until the merge point, then take turns entering into the open lane.

During light traffic

You can merge earlier if there is enough space to do so without slowing traffic.

Learn more about safe, responsible driving from the Ministry of Transportation of Ontario.