Are you transporting him or her in their viv? If so, I can't see why you'd need to do that. I'd make things as normal for your beardie as possible and take them out at rest stops to get some sunlight if it's not too cold. Also, I think people have suggested wrapping up one of those hand warmer packs in something like a sock (to keep from burning your dragon), to keep them warm on the road. Those packs last about 4 hrs per if I remember correctly.