The bicyclist had been traveling north on Second Street, a downhill stretch of road without parking on either side, when the rider struck the rear of a vehicle that was stopped while waiting to make a left-hand turn, Sgt. Bill Fraass said.
The vehicle, which had been stopped for about 15 seconds while waiting to turn from Second Street onto Valley Street, was stopped for oncoming traffic because there are no stop signs for that maneuver, Fraass said.
The bicyclist shattered the vehicle's back window, sustaining a head injury of unknown severity, and was transported to Marin General Hospital, he said.
An investigation of the crash is ongoing, Fraass said.