The thing is, you don't generally get to know the context or the intent. You can't have a discussion with the sign, nor can it lecture you. A rule against starting a fire might be because the land owner doesn't like burnt patches on their meadows, or it might be because the vegetation is super dry and if you set fire to it you kill not only yourself but also all the surrounding villages, or something in between.

You could argue that the sign should include enough context to convince the reader to follow its instructions, but (a) you end up with signs with tons of writing in tiny font that everyone just ignores because TLDR (and yes, these do actually happen quite frequently in parks around here), and (b) if there is some combination of letters you can put on a sign that works to stop people lighting fires, the meadow guy will put that on his sign because he doesn't want fires and those syllables work. So you've just pushed the problem one level back, but the real question remains the same: do you risk doing the thing you want to, or do you respect the sign?

Imagine there’s a military bombing range full of unexploded ordinance. The sign outside the range simply says “Keep off the grass”.

In the situation where context is different than what a reasonable person would expect, it has to be included. Language changes meaning depending on context.

The point is that language is unavoidably ambiguous (I'm sure there's a mathematical information theory proof of this, akin to the Byzantine Generals problem.).

"DANGER!! Unexploded ordinance! High risk of death!" is far less ambiguous than "Keep off grass". The former is sufficiently unambiguous that it will deter any sane person from entering.

In the US, usually the law is structured in such a way that the powers of the police are at the state level. A city or park authority isn’t empowered to restrict their actions in pursuit of her duty.

At the end of the day, as a person living their life, it really isn’t your business to know whether an airplane is intruding on park airspace. You should not drive in the park as a private citizen. If you’re a ambulance driver on official business, you should know what applies to you.

"State Police" (or "State Troopers", or "{$state} Highway Patrol, are different from "County Sherif[s | [Deputies]" and city/town/village police. Each level has a local jurisdiction. A city police officer (a subset of city authorities) tends to have authority to restrict actions according to law. Also, a city or park official may technic'ly have the right to do so according to law & park regulations…although some non-pliable people may force the official to summon police.

For anyone who has read the introduction, that's the only valid answer to that question in the context of this game:

"You might know of some rule in your jurisdiction which overrides local rules, and allows certain classes of vehicles. Please disregard these rules [...]. Again, please answer the question of whether the rule is violated (not whether the violation should be allowed)."

I did read the intro, but I considered police/ambulance to be a "universal" exception, not a "local" one (i.e. not idiosyncratic to a particular jurisdiction.)

(*Certainly there exist failed states where the police/paramedics are corrupt and the park owner is warlord from a rival tribe, etc. but I think that goes beyond a normative reading of the question.)