The accident happened just after 1 a.m. as the motorcyclist, a 32-year-old Kent man, was heading east on the West Seattle Freeway with his passenger, a 22-year-old Puyallup woman, on a 2006 Honda motorcycle.
As the motorcyclist was taking the exit ramp to southbound Interstate 5 at high speed, he lost control. Both he and his passenger were thrown from the motorcycle, the Washington State Patrol reports.
The motorcycle driver was killed in the crash. His name was withheld pending notification of his next of kin.
His passenger was thrown over the side of the bridge into safety netting meant to catch debris from falling onto concrete pavement more than 30 feet below - and it saved her life.
Emergency responders had to disentangle the woman from the net before she was rushed to Harborview Medical Center. She was initially listed in serious condition but was afterwards upgraded to satisfactory condition.
The cause of the crash remains under investigation, but the State Patrol says excessive speed was a factor.
A state Department of Transportation official says the net that saved the woman was put in years ago to protect their crews from falling debris such as tires, hubcaps and other things that might come off moving vehicles.
The crash blocked the roadway for nearly three hours, and it has now reopened.