How does RADAR calculate the speed of a vehicle?

RADAR calculates the speed of a vehicle by measuring the change in frequency of returned signals, which is known as the Doppler effect. When a vehicle approaches the radar unit, the frequency of the emitted radar waves increases; conversely, when it moves away, the frequency decreases. This shift in frequency is directly related to the speed of the vehicle, allowing the RADAR system to determine how fast it is traveling.

The other options highlight methods that do not align with how RADAR functions. Measuring the color of the vehicle is unrelated to speed determination, and while GPS technology is indeed used for tracking positions, it is not how traditional RADAR measures speed. Analyzing tire rotation speed also does not relate to RADAR's operation, as it measures the speed through the reflection of radar signals rather than physical measurements of the vehicle's components.