Laser Detection

How mobile Laser Traps operate
Police Laser Guns work by firing a pulsed beam of light at a vehicle which then measures the time taken for it to return, this can take as little as a third of a second. The beam is very narrow, this allows the enforcement officer to be very precise in which vehicle they want to target. From a motorway bridge any vehicle in a line of traffic could be targeted. The beam fired from the gun is of a conical shape, the further away from the gun, the wider the beam. This causes great problems when fitting a Laser Detector to a vehicle, as complete coverage is very difficult to achieve at short range, with only one sensor.

How the enforcement officer chooses which vehicles to target.
Even though the police have all the high tech equipment for measuring and recording the speed of motorists, it is down to the officer using the equipment to choose which vehicle to target. A lot of people believe that the police are checking every vehicle as they go by, this is not the case. Guidelines state that an officer can only measure the speed of a vehicle that they beleive to be exceeding the posted limit. This is often why a driver with a Laser detector fitted may see a gun or van nearby, but will not get a warning alarm as they drive by. The majority of the time they are targeting the number plate of the vehicle as this is normally vertical to the road, but any part of the vehicle could be used.

Short Range
Short range targeting.
This highlights the difficulties of short range detection. The beam is very narrow and with a single sensor it is not possible to cover both scenarios.

Long Range
Long range laser detection.
At long range it is not possible to choose which part of the vehicle they want to target. On some Laser Guns the sight is bigger than the vehicle. Wherever the detector is fitted it is possible to trigger it.

Following a vehicle being targeted
Following a targeted vehicle.
At short range it is difficult to detect, but if the vehicle in front is targeted from long to medium range it is possible to detect as long as the sensor is fitted the front windscreen.

Rear Detection
Rear laser detection
When the vehicle is targeted from the rear, the laser signal will pass thorough the rear windowscreen and trigger the laser detector as long as no obstructions are in the way.