At night, police cars
will sometimes be parked in 'hidden areas', such as behind a billboard or in a parking lot, and
will be facing traffic looking for speeders or DWI cases. They may also be parked alongside the road or in the breakdown lane on the highway.
Ghost cars
will always have their head lights off, but sometimes the day-running lights
will remain on, giving the headlights a light 'ghostly' appearance. It is also sometimes used to refer to any ordinary
car driving at night with no headlights or just their dayrunners on, but usually the title is reserved for police vehicles.