If they really want to exercise the dog using the car, having it on a leash running next to the car is far safer, but I would only do if they can have two people, so the dog can run on the passenger side, with a person hanging on to the leash and paying attention to the dog, which can then be on the safer side with grass, etc.

Having the dog chase the car just seems like a very bad idea for many reasons. I am glad the dog is home and safe, and hope everyone learns from this!