Police Radar Facts

The Problem with Police Radar

www.floridadrivers.com accessed on 2 March 2003.

Reprinted with permission from the brochure Blind Trust. Blind Trust is a publication of the non-profit organization RADAR (Radio Association Defending Airwave Rights, Inc.).

Traffic Radar Reliability

The use of police traffic radar is so widespread that we naturally assume the technology is reliable. After all, if there were questions about radar”s accuracy, would the courts process speeding violations with such assembly-line efficiency? We tend to take the answer to this question on faith. That may be unfortunate, because radar makes mistakes. Lots of them. Some experts estimate that 10-20 percent of all radar-backed speeding tickets are issued in error; and in the case of radar that is operated from a moving police vehicle the number of bad tickets may be as high as 30 percent! This Brochure {a print version of this info. is available from RADAR) is intended to familiarize the reader with some of the most common radar errors. Our Hope is that more people will realize that traffic radar is not infallible, and will challenge speeding tickets they know they don”t deserve. The end result will be a greater effort by the radar industry to build better products, and by law enforcement to use this technology more responsibly.

Two Kinds of Radar

To understand how radar makes mistakes, it is first necessary to know how radar works. Basically, there are two kinds of radar – traffic radar, and rotating- antenna radar. The latter group includes weather, airport, military and other types of commercial radar. By contrast, police traffic radar uses a stationary single antenna that points in a single direction; does not transmit a modulated signal; and does not use a cathode ray screen to display information.

These three differences are extremely important.

All radar works by transmitting a microwave beam on a specific frequency. Targets that are struck by the beam reflect microwave energy to the antenna, a computer analyzes any changes in frequency and displays this information. Military-commercial types of radar use a sweeping , modulated beam which provides details about an objects” shape, speed, and direction for the operator. By contrast, the stationary beam and digital readout of police traffic radar yield only one piece of information: how fast a target is approaching or receding from the radar. Police traffic radar doesn”t tell its operator which object it is measuring or the direction that the object is traveling, limitations that compel manufacturers to build in certain electronic compromises.