^ +1 to much of that. I think that if all their illegal vehicles were impounded that would be a very effective tactic; it wouldn't stop them doing what they do, but it would stop them coming to a particular area, and moving the problem on seems to be all the law can accomplish these days.
I have no problem with travellers per se, but their way of life is to stay somewhere (on somebody else's property) for a while, while their menfolk go out to find casual work, for cash, and the women and children go out variously shoplifting, burgling, and generally causing a spike in the local petty crime rate.
They make a midden, which they leave for others to clear up, and they make virtually no contribution to society by paying taxes, though that does not stop them taking free medical attention, for example, which the rest of us fund for them. I'm not saying they are necessarily bad people, but their way of life is thoroughly anti-social; honour among thieves, but anyone or thing not part of their community is fair game.
That said, though, it may be that even some travellers are beginning to get the message in the generally-justified hostility they meet everywhere they go. There were two, admittedly only for a couple of days each time, significant gatherings (40-50 caravans) recently locally (weddings), and they actually bagged up some of their rubbish before moving on.