The cop's radar is certainly not a guessometer, when properly calibrated.
Originally Posted by Alan Klein
OTOH, your car's speedometer is absolutely a guessometer...the 6mph 'leeway' that cops allow over the posted speedlimit before pulling you over is merely to give you the benefit of the doubt due to poor calibration of the typical car speedometer. My last car was about 1mph optimistic, my current car is 4-5mph optimistic (indicated 73 mph to be actual 68-69mph). as compared to GPS speed...at indicated 65mph I am holding up traffic.