As long as the car isnt too warm, too cold, and they arent in direct sunlight you should be ok. When i bought Sphinx and Sway from the All Maryland Reptile Show about 3 weeks ago, i brought them home in pillowcases. At the show they came in big plastic containers, but as soon as i was in the parking lot i got them out of there and into the pillow cases i'd brought. I use dark colored ones to help filter as much light out as possible. I then had an approx 4 hour drive back home. I just put them together ( in seperate pillow cases ) into a small spare rubbermaid about the size of 3 shoe boxes and then on the front passenger side floor. Andariel ( Chris ) went with me so he was able to secure the rubbermaid from moving around too much otherwise i would have found a way to keep it from moving. In that spot of the car, there isnt too much direct sunlight or air flow from having the windows down. In my opinion, as long as they are secure from moving around too much, in a darker environment, and kept relatively warm ( the summer season helps .. just gotta watch out that its not too warm ), they are fine to travel. After you would get them home in either case ( vet or show ) its advisable that you dont handle them for at least 3 or 4 days to let them de-stress.