Sure, the dog loves to run alongside when its master is riding the bike. However, that is not always and everywhere necessarily good in every situation. Lots of traffic and other four-legged friends can be dangerous to the man's best friend or force many stops. It also could even make the most faithful companion weak and overwhelmed which a dog should indeed not be. For people traveling longer distances by bike, dog trailers are therefore ideal. The dog can look out of the carrier, take everything in in and does not run alongside the bike all the time. You can then ride at your own pace and always have the dog with you. In nature, he can run free or you can leave him alone.