Many years ago, I had to make regular trips from North London to CCT, which took about an hour, and they got quite used to it. Later, with pigs 3 and 4, I made fortnightly trips from my place to the Pet Rodent Centre to get Kurt's teeth done and again, they got used to it quite well.
For a while, I went out with someone who lived in Suffolk (yes, I know) and Gethin and Celyn were still quite young then, so they made monthly trips of about 4 hours each way and the occasional 2 hour trip to London as well, but they really seemed to enjoy it. In fact, they could tell when I was getting ready to go and got quite excited, popcorning and everything. If it was just an overnight trip or something and they weren't going, they seemed to get really cross that I didn't take them! All I had to say was "road trip" and they went nuts.
I tended to stop about every 1 1/2 hour so they could have a drink (with a syringe) and a cuddle and yes, I got some pretty strange looks from people at motorway services. I remember one person pointing and saying, "Wow, look at that gerbil!"
They went in their travel bag, which was a Sherpa Bag I got from America. It looks something like a sports bag, but has mesh on the sides so they can get air and see out, but its soft and dark. I put a newspaper and vet bed in as well as hay, dry food and veggies. They also had a "mobile home" (basically, a large plastic box on wheels) and I put all their hay, food, blankets, toys, etc. in there in the boot. The Sherpa bag strapped to the back seat belt and they seemed pretty comfy there. Occasionally, you'd get some squeaks - a bit like a couple kids in the back seat.
The Sherpa bag was looking pretty tired, so it's been retired. I couldn't find another, but got a nifty travel bag (I think they are designed for small dogs) which is also a ruck sack and has even more secure straps for the seatbelt. They don't get to make as many trips these days, but they still seem to like it. I think it makes a difference that they were young when they started and they are both fairly laid back (especially Gethin) so take it in their stride. I've got a very good neighbour who comes over daily and feeds them (and even tends to Gethin's impaction problem - now THAT'S a good neighbour!) if I'm just away for a few days.
Mind you, when I was younger, I had a cat that I took in the car from when he was a kitten and he used to love going with me places. I had to be careful he didn't sneak in when I didn't want him to!