Coming to you from Washington State...

From the Seattle Times Eastside bureau

Q: Before the Issaquah-High Point Trail Connector opened last week,
the designated biking route from the Issaquah Highlands to the city's
center was pedaling down Interstate 90, said Lee Haro, project manager
for the connector.
Cyclists on the freeway? Is that allowed?
A: Trooper Jeff Merrill, a State Patrol spokesman, said he receives
many concerned phone calls from motorists who spot bikers on the
freeway.
"It's kind of unusual," he said, but it's legal to ride your bicycle
on part of Interstate 90 — on the shoulder, that is.
Starting from the Eastgate exit in Bellevue, a cyclist could bike east
on the shoulder all the way to Spokane on Interstate 90. Same goes for
the other direction: riding the Interstate 90 westbound shoulder is
fair game until Eastgate, he said.