That’s a good question and I have to believe it depends on where you are, as well as if the land is covered by a local municipality or is state owned (or even federally). I’m sure the state has a lot more leverage for covering themselves than a local municipality does, but as a hiker my understanding is that the local, state or federal government can be sued if you get hurt on their land if your injury is due to their negligence, although I have no idea how that would play out in real life (if a tree falls across the trail and you fall when trying to climb over it who’s fault is it?). That being said, I can see how making a state owned motocross area could have a lot of issues like this come up.

They used to be used for exactly this back in the 70's and 80's. I remember as a kid driving up 95 and specifically waiting to get to that part of the highway to watch them ride for a couple of seconds. Then someone got hurt (naturally) and they closed the land for this use. Same thing has happened at parks and hills all over the northeast for sledding- one person gets hurt, everyone suffers the consequences. Insurance companies up the cost of coverage and it just becomes cheaper for municipalities to close everything off.

Not a bookstore, but the Providence Athenaeum is not just one of the best library spaces in Providence, it's one of the best spaces I've been to in the country.