It's a Northwest bad driver stereotype that's so common, it was parodied in a local Pemco Insurance ad campaign.
Tom McCall, a WashDOT traffic engineer, makes the rule clear: "The expectation is to keep right except to pass."
Driving in the left lane is such a source of road rage, that one driver has taken the law into his own hands and put it on a bumper sticker.
Carson Swink is the creator of the bumper sticker that reads "RCW 46.61.100 Keep right except when passing."
Still don't understand?
Swink reiterated, "It means don't drive in the left lane."
He originally printed the stickers on a whim for friends and family.
"It definitely started out as my rant to Seattle."
They eventually found their way onto Reddit, and now demand for them has blown up like Seattle's rush hour traffic.
Despite Swink's plea to Washington drivers to better abide by this law, there is a little caveat.
"In Seattle, because of the left hand exists, drivers are allowed to be in the left-hand lane regardless," McCall explained.
But once out of the city, these letters and numbers are words to live by.
"Just keep right," McCall said once again. "It'll make everybody happy."
Evening is your guide to Seattle and the Pacific Northwest. Watch it weeknights at 7:30 on KING 5 TV or streaming live on KING5.com. Connect with Evening via Facebook, Twitter, Instagram or email: firstname.lastname@example.org.