The only safe way for your dog to travel in the car is in the backseat in a carseat or safety harness. If he is not secure, he will become a projectile if you have to slam on your brakes or are involved in an accident. Not only will he be injured, but he can injure others in the car.
Dogs should never ride in the front because of the airbags. Too many dogs have been killed when airbags deployed. They can deploy at only 20 mph.
This is a good article about safe car travel with a small dog:
Dog Jaunt air bag - Traveling with a small dog