I occasionally get on I-25 and head to Albuquerque. While I don’t mind the idea of leaving the cat in the house for a day or two, longer trips (like Thanksgiving or Christmas) will pretty much require bringing the cat along. When I brought him from Albuquerque, I learned that he didn’t really like the soft-sided carrier I had and I eventually let him out after about 10 miles on the highway. I already had him in his harness just in case so I put the leash on, tied the leash to the passenger seat giving just enough slack to give him room to stand up, lie down, and turn around without getting off the seat, and drove the next 200 miles in peace. But I don’t really like this method and would feel better if he was buckled into a car seat that buckled into the seat belt.
All of the ones I’ve found online specifically mention dogs. Would one designed for a small dog–say 15 pounds or less–work fine for a cat? I’m looking at no more than four hours on the road, less with no stopping somewhere for food or to rest my leg (no cruise control in the car.) I just don’t want him to be able to get out and wander around the car–I figure he’ll be killed if he gets thrown forward in a crash and when he got out once he kept getting in my sight lines, jumped on my shoulder, tried to go into my footwell, and got himself stuck in the back seat. So tying him down one way or another to the front passenger seat seems like the way to go.