The Washington State Patrol and social workers at Harborview Medical Center in Seattle are working together to determine the man's identity, trooper Mark Francis said.
The man has been unable to speak since the March 26 accident.
He was not carrying identification. Police have not been able to find his family or friends.
The man was struck while apparently trying to cross the freeway about 5 a.m. near the 75th Street SE overpass.
He is believed to be Hispanic and in his 30s. He is about 5-foot-9, 190 pounds and has black hair and brown eyes.
At the time of the accident, he was wearing a blue-and-black backpack and using a walking stick.
Anyone with information should call 360-654-1204.
More Local News Headlines
More problems noted at airport Check fraud ringleader suspect caught TEDx talks bring out some of regionís brightest minds Basking in the moment Front Porch: Snohomish County executive forum Dream shared on social-media prompts EvCC to boost security Arlington thrift shop gives special-needs kids real-world skills Former county ombudsman John Koster files $950K claim
Our new comment system is not supported in IE 7. Please upgrade your browser here.