Doppler effect helped a physicist from Kazan successfully challenge a traffic police fine

The same complex that captures the speed of cars passing by

In Russia, in particular, in Kazan, the traffic police began to use the mobile video recording complexes "KRIS-P" to determine the speed of passing cars. Many motorists believe that the accuracy of such complexes is low, and some manage to successfully challenge traffic police fines, proving in some way their case.

The candidate of physico-mathematical sciences Yuri Goryunov, who received a fine of 500 rubles for speeding at 22 kilometers per hour, was also able to do this. His “Lada-Grant” hit the lens of the mobile photo-radar complex “KRIS-P” in August last year in the Vysokogorsky district of Tatarstan.

“I categorically disagreed with this, because my speedometer showed no more than 80 km / h all the way, I didn’t accelerate. Trying to find an explanation, I began to carefully examine the photos from the “letter of happiness” and drew attention to the fact that the sensor of the photoradar is located below the bottom of my car. As a physicist, I concluded that in such conditions, the propagation of radio waves in this atmospheric layer decreases, and therefore the results of speed measurements are too high. And having studied the documentation of “KRIS-P”, I realized that installing the sensor of the photoradar at an angle smaller than the angle of 25 degrees indicated in the technical characteristics of the complex also leads to a strong overestimate of the vehicle speed measurement result! ”, Said Yuri Goryunov.
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The scientist studied the principle of operation of the mobile complex, including one of the modules, the Iskra speed meter, and went to court. The physicist took with him the text of GOST R-50856-96 “Vehicle Radar Speed ​​Gauges”, as well as information about the conditions of passage of radio waves in the atmosphere and the Doppler effect.

“Of course, many will say that it was easier to pay these unfortunate 500 rubles and not to go through the courts, but I’m such a person, I don’t like it when they deceive me so frankly. If I had really broken, it would be another matter, ”explains Yuri Goryunov.

This case was considered for five sessions. All this time, the judge carefully read the instructions for the "KRIS-P" and "Iskra". The scientist explained his point of view, arguing it with the Doppler effect . According to him, the operating conditions of the complex were violated, and the measurement results are strongly influenced by the properties of the medium where electromagnetic waves propagate. The complex must be installed at a height of not less than 0.5 and not higher than 2 meters, and traffic police representatives do not comply with this condition.

As a result, the court took the side of the plaintiff. The court’s decision stated the following: “As follows from the analysis of factors affecting the result of speed measurement by radar speed measurement, the speed meter operating in automatic mode should take into account the influence of these factors on the measurement result: the vehicle’s direction of movement relative to the direction of propagation of the radio wave The propagation velocity of a radio wave, i.e. consideration of humidity, temperature and air conductivity in the measuring channel. According to the principles of work set out in the Operation Manual of the KRIS-P Photoradar Complex and its Iskra Speed ​​Sensor DA / 210, the KRIS-P Photoradar Kit does not have these functions. Thus, the court concludes that the measurement of the speed of the vehicle by the photoradar complex KRIS-P is not automatic and requires the participation of the operator. Consequently, the complex produces photofixation of an unreliable established violation of the speed limit ”.

Vysokogorsky court decided to cancel the decision on administrative offense. True, the defendant’s party filed an appeal to the Supreme Court, where the claimant’s arguments would be examined again. But the laws of physics are the same for everyone, so one can hope for a positive solution of the issue for the scientist and in the Supreme Court.