How Traffic Laser Works

To measure speed, traffic laser sends out a beam of pulsed infrared light. The beam is tightly focused: at a range of 1000 feet, it’s only about four feet wide.

Infrared is invisible to the naked eye — the operator can’t see it and neither can you. But it is light and it behaves accordingly. It travels in straight lines. And it’s easily reflected.

Traffic laser works as a rangefinder. It sends a pulse, then waits for the reflection from the target car. From the time needed for the pulse to go out and back, and from the speed of light, it calculates distances to the car. These pulses are sent frequently, up to 500 times a second. The changing distance to the target over time is speed.

Laser can’t see over hills or through opaque objects. The laser beam must hit your car directly, line-of-sight from the laser gun, to measure speed. Under ideal conditions, it can read speed in less than one second.

The pencil beam means that, in operation, laser is very different from radar. Radar cannot single out one vehicle in a pack, so the speed reading is usually attributed to the leader. The narrow laser beam reads only the vehicle it strikes.

How Laser Detectors Work

A laser detector is an electronic sensor calibrated for the infrared wavelength used by traffic laser. It is extremely sensitive. And it responds in as little as .006 seconds.

It should be mounted inside the car with the sensor facing through the glass toward the laser. When the beam, or scatter from the beam, strikes the detector, it warns instantly.

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Laser Detector Defense Techniques
Laser Detector False Alarms