Our last cat started RVing when she was 12, she would get motion sick usually in the first 15 minutes on the road but was fine after that, never used a carrier. Never had a problem with her, she died at 17. The next cat has been RVing since she was about 4 months, no carrier, no motion sickness, and she seems to really enjoy the RV. Both are indoor cats although the old one would try to get out and the new one we keep scared of the outdoors, and in 4 years she has never got out and doesn't try. I did a lot of work "plugging up" the holes so the new cat couldn't get places she wasn't supposed to and we get a hold of her when the slides are moved.