We travel with 3 cats. For the most part, they get along. We have 2 litter boxes. When we started traveling in the RV, they started out in a large dog kennel - all together. After we get on the road I'll open the crate door & one of the kitties, Katrina, pops out. She likes to come & sit in my lap & look out the window while we travel. Our big boy cat, Pas, likes to stay in the kennel & only comes out when we stop. This is any stop, for gas, rest or for the night. He immediately wants his food & water made available. And of course, it is.
Katrina is the only one who has "escaped" out the door. Thankfully, it has only been when we have been at a campground. She bolts under the RV, just out of arm's reach. So, one of us will get a broom & scoot her to the other human. Since then, what we have done to help alleviate any of them wanting to bolt out the door is a spray bottle with water. When we know we're going in & out the door a lot, the bottle is sitting on the steps & we can easily spray right through the screen if needed. No more escapes.