When you can, be sure that he's slightly tired from a walk before he has to get in the car. But if you have to drive to areas to walk him, you can make the car itself a more relaxing environment. Be sure he's secure in a crate (the safest method of car restraint) or a doggie seat belt so his movement is somewhat limited. You can have a special stuffed toy or blanket for him in the car, too — and to sweeten the deal, spritz it with Adaptil, a synthetic hormone available at most pet-supply stores that has a soothing effect on dogs. You know the way you feel when you walk into grandma's house when she's been baking cookies? That's how this product can make him feel. Cover the seats, get a chew toy, bone, or frozen stuffed Kong and give that to Rover immediately after he's inside the car. You're shooting for something that will keep him distracted for 15 or 20 minutes once he's moving. You're also looking to give him an appropriate way to relieve his stress — chewing will let him do that, with the added benefit of keeping his mouth full and quiet.