Cookie is the perfect traveller and joins me whenever I go for a carride (except when I do the weekly shoppings because I don't want her to stay behind in the car.
Cook simply jumps in the back, lays down on her pillow and sleeps. I take her with me when I visit my parents. One time there was a terrible traffic jam with stop and go for 4 hours and she couldn't go out for a break until I was home again. That were 6 hours altogether and no complaining.

The cats don't like it. Rudie makes a very big fuzz and screams all the way to the vet. Eddy isn't happy, but accepts it for 20 minutes max.

My RB cat Pishi was fine with carrides. I always took her along to Holland. Those 3 to 4 hours were fine with her. Perfect cat.