Keeping tabs on roads around the world, speed cameras have helped catch lead-footed drivers since 1964 with the invention of the Gatsometer speed camera, or ‘Gatso’. Today’s Gatso speed camera is a radar system that uses radio waves to measure the speed of passing cars. It does this by calculating the time it takes emitted radio waves to return to the camera’s receiver from a moving vehicle, otherwise known as the Doppler effect. As a car passes the speed camera, the frequency at which radio waves rebound increases, which can then be translated into the speed of the vehicle.
When the radar detects speeds that exceed the speed limit, the onboard camera quickly snaps two images of the rear of the vehicle. Along with capturing the registration plates of fast-moving cars, the images also show their position compared to a series of white lines painted on the road in the camera’s view. Although speed is recorded by the camera’s radar system, this series of white lines on the road offers a second way to measure a car’s speed. By comparing the position of the car in the two images against the white lines, the distance travelled in the time the two images were taken can be used to give the vehicle’s speed.