We carry the dog in a crate fastened with straps. This is the safest way to transport a dog in a car. The seatbelt was not practical to fasten the crate. The crate sits in the trunk of our hatchback crossover with the seat in front of it collapsed, so I can visually keep it in check and the dog gets AC. There are also dog "seatbelts" if you carry it on the back seat. It's like a leash with a seatbelt buckle at the end.