We use to rubber tramp with my cat, Spore. It's not easy and I don't typically recommend it, but it can be done, depending on the cat's personality and age. My biggest concerns with traveling with cats, is even with a mellow cat who's really well versed with traveling, like Spore was, a cat is still going to be a cat and go prowling. They'll be there one minute, then gone the next, and you may not see them for hours. If something happens and you need to bolt, and your cat is out and about, they could be screwed. You could develop a call for the cat, but cats are cats, and will only respond when they feel like it.
We ended up leaving Spore behind with my mother last time I was home, after a tornado touched down while we were camping and couldn't find him.... My husband, our dog, and I were running through the woods with golf ball sized hail and lightning flashing like a strobe light, SCREAMING the cat's name. In the end, we found him and got out of there, but that was the straw that broke the camel's back.
That being said, I'd take Spore back in a heart beat and travel with him again if something happened where my mom couldn't keep him and he was going to go to the shelter. I highly doubt that would ever be the case, given my family adores him, but if it ever were, I'd rather him be with us, living it up and being loved with the risk of dying a premature death on the road, then being subjected to the cruelty of the shelter system where he'd just live in a tiny cage as a number, and ultimately be euthanized alone, scared, and unloved.
My recommendation to you and to anyone else out there considering traveling with a cat is if the cat isn't fixed or microchipped, GET IT DONE. A fixed cat doesn't tend to wander far, but if it did and was found and turned in to a shelter, vet, or animal control, they'd be able to contact you. Leash train the cat ASAP. Make sure you get them on the healthiest cat food you can afford. You want to make sure the cat is in the best shape possible, should it need to out run or defend itself. Get the cat use to the sounds of traffic and large groups of people. Do NOT let your cat off leash in cities, especially near sewage drains. If you settle down, observe the area very closely and make sure it's relatively safe. Cats are very curious, and will wander off to explore. If they wander into a sewage drain and get lost or stuck, they're fucked. We only let Spore loose in wooded areas or parks.
Hope this all helped. Good luck to you!
. Took my siamese into work a couple years ago (on way to the vets via bus) and my boss says "Let her out!!" - ha. Spent the next hour trying to corner her and get her into her cat carrier - it was not pretty.
