The principle of speed measuring camera is photoelectric.

In fact, it is not the camera that measures the speed on the road, but the radar. The camera takes a snapshot after receiving radar information. There are two kinds of speed measurement, one is instantaneous speed measurement and the other is interval speed measurement.

The principle of radar velocity measurement is Doppler effect of radar signal. There is a difference between the frequency of radar signal reflected by moving objects and the transmitting frequency, which is called Doppler frequency. The Doppler frequency value is proportional to the moving speed of the object. When the vehicle enters the detection range, the radar will send out two waves of signals to detect the position of the vehicle. When two waves are received, the driving distance is calculated and divided by the time, which is the vehicle speed. When the calculation result exceeds the regulations in the system, the camera mode will be turned on immediately, and the vehicle will naturally overspeed.

In the case of interval speed measurement, the interval speed measurement system mainly arranges two or more monitoring points on the same road section to automatically record the passing time and vehicle characteristics of the vehicle to be measured and calculate the average speed according to the time interval of the passing interval.