I've seen people riding their bikes with their dogs tied on, the dog running beside the bike. I get it, I guess, they are killing two birds with one stone, so to speak; they're exercising and their dogs are exercising too. I think it's a good idea in summary, but in theory and practice it seems very dangerous. If the dog's leash is too long, it could get tangled up in the bike, and if the leash is too short, the dog itself could get caught in the bike. Then there's the matter of navigating traffic and keeping control over the dog, who(m) has its own will and compulsions. Have you ever seen people tie their dogs to their bikes via leash and go for a ride? If you've seen this, how do you feel about it?