Traffic speed camera. Computer artwork of a traffic speed camera marked by yellow and black warning stripes. The camera has been triggered by a speeding vehicle and is taking a picture (as shown by the flash) of the vehicle's numberplate. The camera measures a vehicle's speed using either radio waves or piezoelectric strips embedded in the road. The photograph also records the time, date, location and speed of the vehicle. The film is recovered and processed at regular intervals, and notices are issued to drivers. The warning markings are needed to make the cameras visible to drivers, as required by law in the UK.