I'm fascinated by the fact that my takeaway is the precise opposite of what the author intended. To me, the answer to all of the questions was crystal-clear. Yes, you can academically wonder whether an orbiting space station is a vehicle and whether it's in the park, but the obvious intent of the sign couldn't be clearer. Cars/trucks/motorcycles aren't allowed, and obviously police and ambulances (and fire trucks) do…
Cue ambulance crashing through a wooden bridge over a river because it was never intended to carry the weight, or getting stuck in a tunnel, driving over pedestrians that can't get out of the way because there is no space left, ... . Blindly ignoring a rule because you can is not always a good idea. You might be able to ignore the rule, but you can't ignore the reason why it was put in place.