A speedmeter measures and displays the speed of a moving vehicle and the range at which the speed was measured. Laser speedmeters calculate speed by determining distances - by measuring the time of flight of short pulses of infrared light.
A laser speedmeter may be hand-held:
Here is the same device:
The device has detected a vehicle moving at 51 mph at a distance of 184.2 meters.
The same technology may be used from the inside of a so-called Safety Camera Van:
Here is the inside of the van:
The above image shows a laser speedmeter attached to a tripod, screen and video recorder. The operator has detected a motorist travelling at 119 mph, from a distance of 267 meters. The video may be kept for evidential purposes, and can be used to produce stills. Here is an example still:
Images by North Yorkshire Police and Surrey Police.