Can the employer control the private car?

Hello, our security department of the company has thought about controlling the cars of the employees on the correct tire!? In other words, the boss of the occupational safety and his employee run over the parking lot (about 80 cars) and distribute red or green paper under their windscreen wipers. Red gets a car with summer tires, green one with winter tires. I find the action very questionable, since I think that everyone is responsible for his own car. On the other hand, n page, is the trip to the company also work path, where there is a certain liability for the employer. What do you mean? Is the OK that the company controls the tire and distributes notes, or do they have nothing to do with the private cars??? Greetings, Stefan