If you don’t zipper merge already, drivers will now get a gentle reminder to do so at a congested interchange in Thurston County.

Signage encouraging zipper merging at the U.S. 101 and State Route 8 interchange was uncovered Monday.

It’s part of a pilot project, and the Washington State Department of Transportation will evaluate if it should be expanded statewide.

During the morning commute, drivers on southbound U.S. 101 typically face congestion as cars approach the merge with SR 8. Two lanes reduce to one as U.S. 101 passes underneath SR 8, but WSDOT says most drivers get into the left lane back when signage advises that the right lane will end in less than a mile. This creates a longer line of traffic in the left lane, and the right lane goes mostly unused, according to WSDOT.

“Right lane drivers through there are not cheating,” said WSDOT spokesperson Doug Adamson. “The people who are using the right lane are using all the road that’s built.”

If drivers were to zipper merge – which means riding the right lane all the way to the end and merging by alternating with traffic in the left lane – transportation officials say traffic would improve. When drivers zipper merge correctly, congestion can be reduced as much as 40%, according to the Minnesota State Department of Transportation.

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Crews could extend the second lane all the way under SR 8, but WSDOT says that would be costly and time consuming, because crews would have to tear down the existing bridges and rebuild them with larger and more expensive spans.

“We can use the existing roadway and increase the efficiency through that area, help reduce congestion, as more and more drivers are able to go through this area simply by merging,” Adamson said.