Normative Signs: The Poetry of "Ought"

This sign is in a cable car in Porto, Portugal. It was sent to me by PY Néron.

Interestingly, as PY points out, the sign clearly forbids lighting matches (presumably intending indirectly to forbid smoking?) and also forbids standing/leaning against your seat. But…what’s going on in the other signs? The third sign seems to urge caution when the cable car doors are open. But is mere caution enough when the car is suspended high above the Douro river? Or is the sign just urging caution when hopping out of the car at the end of your journey? It is at least tempting to read that sign as saying, hey, we know you’ll want to open the doors mid-trip, but please do so cautiously.