The Washington State Department of Transportation will be installing new signs at the interchange south of Steamboat Island Road where southbound U.S. Highway 101 merges with State Route 8. These signs will better illustrate the “Zipper Merge” at that interchange. The DOT also produced a video:

Sharing, taking turns, treating others as you would want to be treated – turns out the lessons we learned as kids will help South Sounders navigate a new “zipper merge” at the US 101 and State Route 8 interchange. It’s a practical solution to an old problem that will rely on travelers taking that “Northwest nice” adage to heart.

As always, being polite and cooperative has advantages. In this case, it will help reduce congestion, delays, and the kind of annoying backups that can turn a sweet demeanor sour.

The situation
During the morning commute, southbound US 101 near Steamboat Island outside Olympia has regular congestion. Two lanes reduce to one where the highway passes under SR 8. Most commuters merge into the left lane after signs advise that the right lane ends in less than a mile.

All of those vehicles crammed into one lane creates a long line of slower-moving travelers slogging through the interchange. All the while, the right lane goes mostly unused, except for a few who zoom by, eliciting scowls and scorn from all of the drivers waiting in line.

Why not expand the roadway?
Extension of a second lane under SR 8would eliminate the bottleneck, but it would require crews to demolish two existing bridges and rebuild them with much larger and more expensive spans – a very expensive and time-consuming endeavor.

Enter the zipper merge
The zipper merge is all about making the most of the existing roadway by having drivers rethink what it means to “drive nice.” Instead of merging while up the hill near Steamboat Island, we want drivers to merge closer to the area where the lane ends. Vehicles will politely switch off, letting their neighbor proceed at a nice steady speed, just like a zipper.
Although it might feel like cheating, merging at this location in this fashion will help cut congestion and increase the efficiency of the existing highway. Nobody is cheating or cutting in line. When you drive nice in the zipper, all of the unused road gets used, so we can all get there with reduced congestion and reduced scowling.

What’s the timeline?
We will install new signs in late June to encourage use of the zipper merge. This effort is a pilot project that we will evaluate for possible use in other areas.