Long away trips always seem to bring out the atmosphere. See also Carlisle and Middlesborough. I think it's a combination of "I've come all this way so may as well enjoy it", extra time for drinking from setting off earlier and the Northern exiles bringing mates and making a day of it. I certainly used to bring non-OUFC supporting friends along when I lived is Salford.
There are also some right nutters who turn up at our Northern away days - I'll never forget witnessing an argument between one of them and a tracksuit bedecked scally enroute to Rochdale that ended up with said Oxford fan pinned up against the door of a Sprinter train. The disagreement mainly involved Starburst.