In some states it's illegal to carry bikes on a trunk mount if the bikes obscure your tail lights or tag (almost all do). I've read reports of people getting tickets for this, but it's one of those things that's highly subjective. I have a home-built rack on the back of my Jeep that bolts to the tailgate in place of the spare tire carrier that works very well. If I drove a car I think I would go with the roof rack...