Unfortunately, there is a big problem with this sort of calibration testing. There are two types of circuits in the unit, frequency circuits and counting circuits. Flicking the calibration switch tests only the counting circuits. In short, if the frequency circuit is not calibrated, the radar unit may well be inaccurate.
The fact that an internal “calibrate†test isn’t a substitute for a tuning fork explains why it’s so important in any traffic trial involving the use of radar to cross‑examine the officer and see whether she really did use a tuning fork before you were ticketed. Typically, they are required to use the tuning fork at the beginning and end of their shifts.
d. Pulling You Over As Part of a Group of Cars
In situations where several cars proceed over the speed limit, some especially any zealous officers will take a radar reading on the “lead†vehicle and then pull it over, along with one or two followers. In court, the officer will try to use the reading for the first vehicle as the speed for everyone else.
13. Is the laser accurate in measuring a driver’s speed?
Laser devices, also known as LIDAR (light distance and ranging), use a time/distance calculation to measure speed. The devices aim a narrow band of light at the target vehicle and measure the time it takes to receive the reflected light. Because the speed of both the original light pulse and its reflection are traveling at the same speed (the speed of light), differences in the time it takes the transmitted light to strike the target vehicle and return can be used to calculate the speed of the vehicle. Unlike radar, lasers can pinpoint specific vehicles in heavy traffic.
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