In California a vehicle has to be clearly marked as a police vehicle to pull you over. It's the law. Also only CHP has jurisdiction on the freeways. If you run a stop sign on city streets then get on the freeway, the police officer can follow you and pull you over and ticket you or the Cali stop. I only ever slowed down for actual CHP on the freeways. It infuriated me to see 4 lanes of traffic going 65 because some cop was in a marked car on his daily commute to work. On my bike i'd split right past to acres and acres of open freeway in front of me. In the car i'd just sit and seethe.