Teaching a horse to drive

i think you may have missed a step.  when i started my youngsters, everyone starts by learning to longe.  once the walk/trot/canter/WHOA (lots of work on that since driving is so important that you only should be asking your horse to stop once) is going well in both directions, i would introduce the cirsingle and bridle.  you are still longing but off the sircingle.  if you want to use both lines that is fine.... just let it drop onto the hocks.  is there for when you ask them to turn away from you to go the other direction.

if you have a draft or driving club in your area (google it... you'd be surprized!) and look for more help and lessons.  

As with what Double Barrel said, you need to go back to the very basics and start fresh. Can you have someone be at his head when your working him to keep him on track? Also, if you tell me where you are, I can see if there are any draft folks or a driving club you can ask for help from. Driving is a great sport but is one of the most dangerous ones as you not only have the driving animal, you have the cart or vehicle as well to think about, so you don't always catch the more subtle body cue's that something is about to go south, and when it does, you can't just bail.

@GreySorrel

As with what Double Barrel said, you need to go back to the very basics and start fresh. Can you have someone be at his head when your working him to keep him on track? Also, if you tell me where you are, I can see if there are any draft folks or a driving club you can ask for help from. Driving is a great sport but is one of the most dangerous ones as you not only have the driving animal, you have the cart or vehicle as well to think about, so you don't always catch the more subtle body cue's that something is about to go south, and when it does, you can't just bail.

I think you should try the reward system. Well, it seems like it was posted years ago. Hope he already mastered the things you taught!

I keep going back here when I use google for the same problem. Are there any other forums with the same issue? preferrably more recent?

What are you looking for Cal?  You might try Facebook.  There are any number of horse forums there.  If you have an issue with driving, I could likely help you with it some.