Scotts Valley Police have sent out an alert advising drivers to avoid southbound Highway 17 at Mount Hermon Road because of a major crash.
According to the California Highway Patrol, three 18-year-old women were traveling from Scotts Valley when the driver made a sharp turn and crashed through the guardrail on the right shoulder.
The accident occurred just before 1 p.m.
The driver was transported by air ambulance to a Bay Area trauma center with serious injuries. One passenger was transported to Dominican Hospital for treatment of minor injuries. The other was released to her mother.
At this time, CHP officers do not believe drugs or alcohol were factors in the crash.