A dog must be held in somehow. A running cat or another dog might get your dog very excited. A dog car seat belt belt harness with a carabiner under the belly to somethinig in the bottom of a basket can keep the dog in, but allow him to move around a little. A restraint to the collar is either too short for comfort or too long letting the dog over the edge a little. We have a couple thousand miles on this set up. This coming summer will be year six. The short legs of a corgi make this harness work perfectly, the more normal legs of another breed might be harder to get things just right.