I was going to title this, ‘Unclear on the concept,’ but decided not to comment in that way. It’s possible the two drivers didn’t see the sign, or saw it and didn’t care. Either way, they have a reasonable chance of getting away with it. This isn’t a heavily policed area, and even if a cop goes by, there’s a fair chance they’d simply ignore the transgression. The most likely case for something happening is if one of the people who lives in the vicinity complains.
The sign is at the top of a busy trail down to the Captain Cook Monument. A redesign of the road junction nearby created new parking opportunities and this has resulted in a surge in people using the trail. With more use, word gets out and soon the trail will be overused, the shoreline around the monument littered with trash, and the waters and coral in the bay damaged and degraded.
Not that this is the fault of these two drivers, but since they’re clearly breaking the law, let’s blame them for everything anyway.