It might be worth pointing out that not everyone who lives in a vehicle or a tent is a traveller. There are certain streets in Bristol, and I'm sure it's the same in every big city and some not so big ones, with inhabited camper vans, converted buses and so on permanently (or would be permanently if they didn't occasionally get moved on) parked on them. I haven't heard reports of crime and destruction associated with these but it still causes problems, most obviously with rubbish and drains. But the point is that the people living in them aren't Gypsies, New Age travellers or even moving their vehicles, they're people who'd like to live in a house but can't afford to. The same, more dramatically, with all the tents in the corners of parks.