We had two cats that were 'people' cats, not 'house' cats, and went about with us, recognising the car or where we were as 'home.' They had their own seat in the car at window level, and they would sit unfettered, interestedly surveying the traffic and scenery for about three hours at a stretch until they wanted a nosy and a pee break.
They would wear harnesses when we were travelling in other vehicles and ferries, seeming to understand that a harness meant an adventure, but as soon as we arrived and settled, they would lie down and work the harnesses off with their back feet.
We started taking them about when they were big kittens. One cat was a Siamese, and that helped, because dogs like to chase, and Siamese back up their mates.