In California, the vehicle code applies to all vehicles, including bicycles. Pretty hefty fine for running a red light or stop sign.

When I went to college at a California state university I would watch police officers pulling over bicyclists on a regular basis for failing to stop at stop signs. Every time I had time to wait and watch I would see the officer issuing a citation to the cyclist, most likely for a violation of California vehicle code. They would do it fairly regularly near a bus stop I would wait at, at the bottom of a very long hill.