Are radar detectors worth buying?

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Inside-the-cab view of a Valentine One radar detector.

A radar detector may help you avoid a speeding ticket, but the reliability of such devices is questionable. (Photo Credit: CC BY-ND/Horace Ko/Flickr)

Car Deal Expert does not endorse speeding, but we recognize that such law-bending is prevalent and commonly accepted. That’s why a certain segment of the driving population has used radar detectors since they were first introduced in the 1970s. But are radar detectors effective? Many experts believe they’ve become obsolete.

How radar guns work

Measuring vehicle speed with a radar gun is pretty basic. A police radar gun is a combination radio transmitter and receiver. Radio waves move through the air at a constant speed, and when an object blocks the path of the wave, it bounces back to the emitting device.

Due to the Doppler shift phenomenon, when a car moves through the radio signal, the frequency of the wave changes. Depending upon how much the frequency changes, police can determine how quickly a car is moving toward or away from the radar gun. This computation can even be made if the radar gun is moving, such as when it is mounted on the dash of a moving patrol car.

That’s the old-fashioned radio device, however. Today, police also have Lidar guns, which use infrared light. This laser speed gun uses concentrated light to clock the time it takes for a burst of light to reach a car, bounce off and return to the Lidar device. Rather than measuring wave frequency, Lidar uses many short bursts of infrared light to collect several hundred samples in less than half a second. This provides the most accurate reading possible, although laser systems are only effective at short distances.

Understanding radar detectors

In essence, a radar detector is a radio receiver that pings when police radar gun frequency is detected. When the police expand the range, old detection devices become obsolete. This detection technique is only effective from a distance, however. If a police car pulls behind you and turns on the radar to target your vehicle specifically, your warning won’t come fast enough.

Radar detectors aren’t legal in all states, so it pays to research your state’s laws before investing in a product. Part of the reason for this is that some high-end detectors also serve as transmitters that produce a jamming signal, replicating the original frequency of the radar gun so that an echo signal is perceived by police, making any reading unusable.

Modern radar detectors are also light-sensitive, to defend against Lidar guns. Drivers sometimes reduce the reflectivity of their vehicle, which can also make it more difficult for Lidar to receive a clean bounce-back. Laser jammers that use LEDs to produce light that confuses Lidars also exist.

Safe, legal driving is the best way

No radar detection or jamming equipment is 100 percent effective. Neither is police technology, for that matter. Considering that not all field officers who use radar guns are properly trained, many speeding tickets are thrown out of court. The best defense against speeding tickets is to simply stay within safe, legal limits.

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