I dont think it has anything to do with having the same name has another film, there are tons of films made that have the same name and it makes no difference to the title, it only becomes an issue when it shares it's name with a really famous film, then they'd have to change it.
It's name was changed for release over here because it didn't do very well in the States when it was released with the title 'Joyride.' So they changed it so that the British public wouldn't associate this film with a film they had heard flopped in the US. Plus I guess they want to see if it'll attract more movie goers with a different title, they do it a lot. Like 'Reindeer Games' got changed to 'Deception'. 'Roadkill' suits the film far better anyway IMO, I dont get why they called it 'Joyride' instead.