LIDAR

A somewhat new technology used by law enforcement for measuring speed is LIDAR, which is an acronym for Light Detection and Ranging. These devices use an infrared light wave that is emitted at specific frequencies that allow the beam to focus on an extremely narrow target area.

LIDAR devices are usually hand-held and used by police as they sit in their patrol cars on the side of the road. The waves can be emitted through the glass of a police car, but this reduces the device's range. For this reason, police aim the apparatus out of an opened window or as they stand outside their car.

LIDAR has a maximum effective range of about 2,000 feet. The device's capabilities are greatly reduced in poor weather conditions such as humid, foggy, or rainy days because water absorbs infrared light.

To determine a vehicle's speed using LIDAR, a police officer aims the laser at an approaching car and activates the device by pressing a trigger. The vehicle's speed is then displayed on a small screen.

If the measurement the officer receives exceeds the speed limit, the officer flags down the car and writes a speeding ticket. One advantage of this technology is that the officer can show the driver the speed recorded by the device on the screen along with the distance at which the speed was monitored.

Another advantage is that motorists are completely unaware that the device is in use, and therefore, cannot adjust their speeds before a reading is taken. LIDAR uses light in the invisible infrared section of the electromagnetic spectrum, which is undetectable by radar detectors.

LIDAR works in a very similar manner to radar devices; it can quickly and accurately measure the distance from the LIDAR device to the target vehicle and repeat this measurement many times in only a few seconds.

When used for objects less than one-quarter of a mile away, the beam can expand across six or eight lanes of traffic. LIDAR is usually quite successful and effective in locating offenders. The device, when used properly, has only a 1/10-mile-per-hour margin of error.