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Ask-A-Cop - Radar and Police    
Tuesday, May 06 2008 @ 04:28 PM GMT+4
Contributed by: BrattPoliceDept

Police"What are the rules/regulations an officer has to follow when using radar for speeding?
• Do they have to calibrate the radar gun after each use? If so, how do they do it?
• Do they have to maintain a log for calibrating the radar gun?
• Do they have to maintain a log that that particular radar gun was calibrated while installed in a certain vehicle?


• Etc etc.

What other requirements concerning using a radar gun do they have under Vermont state law?

Thanks!"

Radar, which is short for Doppler Radar, is a well established method of speed enforcement. It’s named after a scientist named Christian Doppler who experimented with the Doppler effect. This is the change in wavelength of a wave as perceived when the object sending the wave is moving at a different speed than the observer. This works for sound waves, water waves, and radar waves. For sound, think of a car horn sounding as the car drives by you. As it passes, the tone changes. That is because it is moving and you are not. That is the Doppler effect at work.

Now, to answer your questions. Police Doppler radars are calibrated by the manufacturer and come with a certificate indicating such. Vermont law does not require that the unit be certified again. However it must be regularly tested.

There are three basic tests that an officer conducts on a radar unit. First, he puts the radar through a brief series of internal tests where the machine checks to make sure its electronics are working properly. The officer then checks to make sure that all the display lights are functioning properly. Finally, the officer uses tuning forks to simulate a speeding vehicle. The forks are each designated with a specific speed, which is printed on them. When the forks are held in front of the radar unit, it should display the appropriate speed.

Most officers test their radar unit at the beginning of their shift. It is then tested again at the end. Some officers test it immediately after writing a ticket and others wait and test it at the end of a shift. Either way, it must be working both before and after the ticket is written. If it is not, the ticket is voided and the radar is sent away for repairs.

There is nothing in Vermont law or court decisions that require a log to be kept of testing or installation. However, for each specific ticket, the officer must be able to testify regarding which radar he had, the fact that it was certified by the manufacturer, and that it was properly tested. The Brattleboro Police Department does keep records on which radar is installed in which vehicle. A computer program is also used at BPD to track hand held radar units that are not installed in vehicles.

If you have a question for the Brattleboro Police Ask-A-Cop, please email it to info@ibrattleboro.com and put “Ask-A-Cop” in the subject line.

 

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