Many people have asked me how to teach their horse to drive. I always answer them by saying that they should seek professional help - driving is a wonderful event but things can go wrong very quickly.
I did train both of my horses to drive but did not hesistate to ask for professional help. I also had two exceptional individuals who had a strong affinity for the sport which continued throughout their career and had over 15 years of experience with horses prior to beginning driving.
This was my dream tandem which I never got to hitch; the wonders of Photoshop shows you what might have been.