we do that. we go out to the grid roads where a car other then your own is VERY rare. and we let the dogs out to run beside the van, and we drive really really really slow, and they tend to stay in the feilds beside the road anyway. the dogs anjoy it, its good exersize for them, and they get a much better workout then they could ever get on a leashed walk, or a run in the park. why? because some of our dogs are velcro dogs, if you are standing right their they will not leave you side, which makes it difficult to run them.