The CHP Monday was investigating an overturned Honda on Calistoga Road and an injured driver.
The car was on its roof near a blind curve on the route connecting Napa County to east Santa Rosa. The crash, near St. Helena Road, was reported at about 7:50 a.m.
A woman, believed to be the driver, was found out of the wrecked car and walking. An ambulance was enroute, according to the CHP.