My 19-yr. old Manx has travelled everywhere with me. He doesn't seem to mind being on the road and he certainly appears to enjoy all the loving attention he gets when we arrive.
I drive an Escape
and with a portion of the back seat laying down, a good-sized dog crate sits very well there. All Bobby's 'comfort's of home' are in the crate...his food, water, bed and a smaller litter box. This helps to keep the bits and pieces of litter, food, etc from scattering throughout the vehicle. And it means I don't have to worry about him inadvertantly slipping out when I stop for gas or getting under the driver's seat to come crawling out under-foot when I'm driving. He resisted a little when I first set up this alternative to his having free rein of the car but he has got use to it now and sleeps comfortably while I drive. Or sometimes he just sits up and watches out the windows
Bobby was already an senior cat when he started travelling with me. I felt he had got to old to be left at home in a kennel or with a cat-sitter. I worried about his health while I was away so decided we'd try this and he seems quite content to just be along.
I tow a 4500 Trillium
with a front dinette so the bed is made up permanently. Bobby's litter-box in kept out of sight (and smell) under the street-side bench, under the bed. Fortunately, I have an outsde access door to this area and can attend to daily cleaning from the outside. The drop-down hatch on the inside keeps it accessible to Bobby.
Since I am often travelling by myself, having my cat along for company and entertainment adds to my pleasure immensely. He never argues, loves to snuggle at bedtime and is just about the perfect companion.