The collision was reported at 6:47 a.m. at the off-ramp from northbound Highway 101 to East Washington Street.
A 68-year-old man was walking his bicycle in a crosswalk on a green light when a car turning right from the off-ramp struck the bike and knocked him to the ground, police said.
The man told police that the driver of the car got out and offered him $60. When he said he was injured and that she needed to wait, she allegedly said, "I have to get to my sisters," then got back in her car and fled east on East Washington Street, according to police.
The man suffered minor injuries and there was moderate damage to his bicycle, police said.
The suspect is described as a white woman in her late 40s or early 50s with brown hair, wearing a brown sweater and light blue pants. Her car is described as a green, newer-model Volvo sedan with a license plate ending in 661 or 663, police said.
Anyone with information about the case is asked to call Petaluma police Officer Bert Walker at (707) 778-4455 and reference report number 12-4349.