If you have two or more cats you need to take to the vet, what is the best way to safely do this. If you have only two cats and they are kittens or small cats than a big carrier might be fine but still might be uncomfortable for them.
When my cats were younger I used to put them in the same cage, but as they became adults, I bought two medium sized carriers so they are comfortable and not getting in each others way.
For extra safety measure, I put the cages in the back seat and put seat belts around them as I want them to be safe as well in event of an accident. I consider them my children after all.