My mates dad has got a motorbike shop and a short wheelbase, low top tranny van, he can get 2 trials bikes in, (motorbikes), pretty easily so I'm guessing 2 road bikes would be fine, just got to think about the sticky out bits, like handle bars and footpegs. They are pretty cheap to buy I think, but not to run, theirs is 10 years old and it's still going strong.