I agree that the police car is a vehicle and and it is a violation.
That's the easiest reading. In a real example, though, there'd be law or authority quoted, and you can be sure that's there would be an exception for emergency vehicles. That doesn't change the meaning of the sign in isolation.
Could be an exception... or not. Some prohibitions come from hazards like "this won't hold your weight" or "this could flood unexpectedly". And there's no emergency vehicle exceptions.
I had my closest park in mind when answering. It has a river and multiple wooden bridges to access. Also, the ground floods sometimes in the winter and some paths are too soft for a car. No way an ambulance or firetruck is going to get in the park. They could try, but would loss more time than doing it on foot, or a bridge would collapse under their weight.
The issue this is inspired from was pretty interesting [0], and notably very few things were exempted from the rules leading to interesting debates on how the rules should be interpreted
That's the easiest reading. In a real example, though, there'd be law or authority quoted, and you can be sure that's there would be an exception for emergency vehicles. That doesn't change the meaning of the sign in isolation.