I took a first aid course for pets, and the teacher strongly suggested seat belts for dogs to keep them from projecting forward during a crash. I found some at The Company of Animals that are padded and really easy to use. You just put on the harness and click it into the car’s eat belt.
Here is young Kai, modeling his new doggy seat belt. His mom said it helped a lot when they went to the Lake recently. He is only 5 months old, and kept him from wiggling around too much!