What does traffic radar determine vehicle speeds by measuring?

Traffic radar determines vehicle speeds primarily by utilizing the Doppler effect of the radar signal. When radar waves are emitted and reflect off a moving vehicle, the frequency of the returned signal changes based on the speed and direction of the vehicle relative to the radar device. This shift in frequency is directly proportional to the speed of the vehicle, allowing the radar to calculate its speed accurately.

Additionally, while the amplitude and angle of incidence of the radar signal can provide other information, they are not used to determine speed. Amplitude relates more to signal strength than to speed, and the angle of incidence affects how the signal is perceived but does not influence the calculation of speed in the context of radar measurement. Therefore, understanding the Doppler effect is crucial for comprehending how traffic radar functions effectively in measuring vehicle speeds.