How does radar measure the speed of a vehicle?

Radar measures the speed of a vehicle primarily through the Doppler effect. This phenomenon occurs when a wave source moves relative to an observer, resulting in a change in the frequency of the wave. In the context of radar, when the radar waves are emitted and then reflected back from a moving vehicle, the frequency of the returned waves changes depending on whether the vehicle is approaching or receding from the radar unit. By analyzing this frequency shift, the radar system can calculate the speed of the vehicle.

The Doppler effect is crucial in this process because it allows for accurate and instant speed measurement, making radar a highly effective tool for law enforcement and traffic monitoring. This method is reliable in various conditions and can capture the speed of vehicles without needing to physically track their movement over a distance.

Other methods listed, such as analyzing color, measuring distance traveled or tracking GPS coordinates, do not provide the direct and instantaneous measurement of speed that the Doppler effect does. Consequently, these approaches are not utilized in radar-based speed detection.