Already in the classical period the blind have been guided by dogs. It's easy to imagine how much assistance the dogs have given in enhancing the mobility of the blind. The dog was able to keep direction and find the way to doors. It also provided companionship and security. We can read books about many famous guide dogs in the 18th and 19th centuries. The dogs were trained to be guides by the blind and with the blind.
Guide dog training has three fields; city training, rural training and obedience training. Modern community planning and heavy traffic make extra demands on using a guide dog. Moving around in cities is complicated, and it's difficult for the blind person to train a dog on his own in a city. Fixed points, such as curbs, are often missing, and in such cases it's difficult for the guide dog user to know where the pedestrian crossing starts. The dogs have to be trained more and more custom-made depending on the surroundings they are going to work.