Most drivers wanting to make better time on the open road will invest in one of those expensive radar detectors. However, this device will not work against a gun type radar unit in which the radar signal is not present until the cop has your car in his sights and pulls the trigger. Then it is TOO LATE for you to slow down. A better method is to continuously jam any signal with a radar signal of your own. I have tested this idea with the cooperation of a local cop and found that his unit reads random numbers when my car approached him. It is surprisingly easy to make a low power radar transmitter. A nifty little semiconductor called a Gunn Diode will generate microwaves when supplied with the 5 to 10 volt DC and enclosed in the correct size cavity (resonator). An 8 to 3 terminal regulator can be used to get this voltage from a car's 12v system.
However, the correct construction and tuning of the cavity is difficult without good microwave measurement equipment. Police radars commonly operate on the K band at 22 GHz. Or more often on the X band at 10«25 GHz. most microwave intruder alarms and motion detectors (mounted over automatic doors in supermarkets & banks, etc.) contain a Gunn type transmitter/receiver combination that transmits about 10 kilowatts at 10«25 GHz. These units work perfectly as jammers. If you cannot get one locally, write to Microwave Associates in Burlington, Massachusetts and ask them for info on 'Gunnplexers' for ham radio use. When you get the unit it may be mounted in a plastic box on the dash or in a weather-proof enclosure behind the PLASTIC grille. Switch on the power when on an open highway. The unit will not jam radar to the side or behind the car so don't go speeding past the radar trap. An interesting phenomena you will notice is that the drivers who are in front of you who are using detectors will hit their brakes as you approach large metal signs and bridges. Your signal is bouncing off of these objects and triggering their radar detectors!
PS If you are interested in this sort of thing, get a copy of POPULAR COMMUNICATIONS. The ads in there tell you where you can get all kinds of info on all kinds of neat equipment for all kinds of neat things!