I-205 - Ramp to SR 14 Zipper Merge Pilot Project - Zipper Merge

WSDOT Zipper Merge - how to navigate a zipper merge

A common misconception of late merging is that it's rude or cheating when a driver “cuts” in front of other drivers waiting in the thru lane. The idea behind the Zipper Merge is that drivers use the full length of all lanes during congested periods to improve efficiency. To the driver, that means less delay, and shorter backups. If everyone merged early, backups could extend to a mile or even longer.

When drivers use zipper merging, cars in the merge lane drive all the way to the end of the lane and takes turns merging, one by one, into moving traffic. By encouraging drivers to use the entire merge lane, the zipper merge can cut congestion up to 40 percent. Studies also show that the zipper merge greatly improves traffic flow. As traffic flow increases, vehicle throughput increases. When more cars get through, you get to your destination quicker. Zipper merging provides benefits to all users, but the key is everyone must take their turn at the merge point.