Monday, June 10, 2019

Zipper merge - applying the "taking turns" approach to keep traffic moving

New signage at US 101 and SR 8 relies on lessons from grade school to zip commuters through

By Doug Adamson

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 8 would 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.

2 comments:

Mark Messinger said...

Thanks, WSDOT, for selecting the US-101 to WA-8 merge for a pilot of the "zipper merge."

Residents, especially in the Steamboat Peninsula/Griffin area, have sought this improvement for some time. In morning drive-time, particularly (and especially when weather is poor), traffic can back up almost to the on-ramp from Steamboat Island Road. That creates a potentially dangerous situation, with drivers entering the roadway and then attempting to move into the left lane, as fast as possible, to queue up. All the while the right lane goes largely un-used. Hopefully, this improved signage will dramatically improve the situation during periods of congestion.

Liz said...

I have been driving this route for 13 years. It was not always like this. The biggest issue are dangerous drivers who do not merge but race to the end and force themselves over, often suddenly, or even paralleling someone on the shoulder. Another area where this problem is occurring recently is heading South, when traffic approaches the I-5 105 Capital exit. That is an exit only lane, during afternoon commute people use it as a right hand passing lane. Very dangerous.

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