This reminded me of my experience with Harley and the cat carrier.
I always bring my 2 cats along when I take my month-long visit to Cape Cod to stay in the family cottage and do some art fairs, and have had success using a grid that goes behind the front seats to keep the cats in the back of the wagon. I put a litter box back there and provide several comfy nooks for them to shelter in among all the art fair gear. They usually complain for the first 15 minutes of the trip, then settle down and sleep for most of the rest of the 16 hour drive. I've never had any trouble until last summer.
After Oliver died the year before and Smokey was lonely, we adopted little black Harley from the pet refuge. He was the most hyper cat I've ever had, super curious and active. I took him for many short rides to get him used to the car and he seemed to enjoy it. But the long trip was a different matter! After about a half hour he started pushing his way into the front seat, and pretty soon I realized that this wasn't going to work on the Interstate, so just before we went onto the Ohio turnpike I stopped in a WalMart and bought their plastic cat carrier, the kind that comes in 2 pieces that snap together, and popped Harley into it. 20 miles later I glanced into the rear view mirror and saw a black arm reaching out of the seam of the carrier. Harley had managed to unsnap one of the connections and was trying to squeeze out! Luckily I had my art fair tool bag with me, stopped in the next rest stop, got out a length of rope and tied the carrier together. I had to let him out every time I stopped so he could use the litter box, but he behaved well in the carrier from then on. This summer I plan to use a large cage for him that will give him more room and can hold a small litter box, too. Wish us luck!