California laws concerning police cars are designed to promote and enhance the safety of law enforcement officers, drivers and pedestrians. Laws in California dictate behavior of the officer driving the police car, the behavior of other drivers around police cars and the physical appearance of the cars.
Police cars use one of two methods to signal a driver to pull over. One sign involves the flashing of the bright red light in the windshield of the police car. Another method involves the usage of a public address speaker on the front of the police car, which the officer will use to tell you to pull over.
"Move Over" Law
The "move over" law instructs drivers on the appropriate driving behavior concerning police cars and other types of emergency vehicles. Senate Bill 159 requires drivers to reduce their speed and move at least one lane over, if possible, when passing emergency vehicles or tow trucks. If a driver does not follow this law, they are subject to a fine of up to $50 (as of 2010).
Unmarked cars are legal in California and undercover officers have the authority to pull drivers over, which they usually do using hand signals. As part of California Vehicle Code Section 40804, any officer whose primary duty is maintaining traffic and enforcing the vehicle code must be in a marked car and in uniform. If the officer in charge of enforcing vehicle code is not in a marked car, their citation will not be valid and they may not be a witness in a trial for any citation they issue while in the unmarked car.
Section 40804 of California vehicle code is sometimes interpreted as meaning that no officers in unmarked cars can issue traffic citations, including speeding offenses. (ref4) This is not true, as officers in unmarked cars can perform this duty as long as their primary law enforcement duty is something other than enforcing the vehicle code.