It's amazing how many people can't follow the instructions, without realising their proving the creators point. Even while arguing the creator is wrong!
This all ain’t easy.
But I don’t need to to allow ambulances. I think this is the core of what many engineers fundamentally don’t get about rules and laws in society?
The framing of the rules clearly places this rule firmly in the real world, in a real park.
I've heard it said that common sense is just what naive people assume is obvious.
I'm not sure about that but I do know that people often disagree on what is and isn't common sense.
I guess this is why English Common Law works. We use precedence to argue about how the words of the law should be interpreted and at least try to flush out ambiguity.
The instructions specifically say not to apply this kind of logic.
GGP made up the sign. The instructions describe a rule, not a sign.
In both law and real life, there is a common understanding (to use your term) that rules may be violated for the greater good. Does driving an ambulance into the park violate the letter of the rule? Yes, but it's still OK because we give emergency vehicles wide leeway to break rules so they can save lives. Judaism even encodes this in a general principle: https://en.wikipedia.org/wiki/Pikuach_nefesh