Speed cameras detect vehicles going over the speed limit. The cameras then take a picture of the vehicles' license plates and send the images to local law enforcement. The cameras can be in a fixed position or equipped in mobile units, typically vans.
Municipalities determine where speed cameras are needed. In areas of frequent traffic accidents or habitual speeders, mobile speed cameras are deployed to help enforce speed laws.
Speed cameras are generally operated from vans. They may be operated from inside a vehicle, mounted outside a vehicle or on a tripod outside the vehicle. To ensure accurate coverage, multiple cameras may be used at each position. The cameras monitor both directions of traffic as well as take pictures of the front and back of an offending vehicle.
Mobile cameras are activated when a vehicle crosses a radar or laser beam. Once triggered, the camera takes two pictures half a second apart. The image is then double-checked by an operative reviewing markings on the road to ensure the accuracy of the speed report.
