Fixed Speed Cameras
These cameras come in many forms, some free standing on poles; others mounted on bridges or overhead gantries.
The cameras may consist
of a box for taking photographs, as
well as a
smaller box for the flash, or only a single box containing all the
instruments.
Recently introduced infrared cameras, do not emit a blinding flash and can therefore be used to take front-on photographs showing the driver's face.
Most states are now starting to replace older analogue film fixed cameras with modern digital variants.
Fixed speed cameras can use Doppler RADAR or Piezo strips embedded in the road to measure a vehicle's speed as it passes the camera.
However ANPR technology is also used to time vehicles between two or more fixed cameras that are a known distance apart (typically at least several kilometers). The longer distance over which the speed is measured prevents drivers from slowing down momentarily for a camera before speeding up again. The SAFE-T-CAM system uses this technology, but was designed to only targets heavy vehicles. Newer ANPR cameras in Victoria are able to target any vehicle.
(Source: Wikipedia)