Yeah I would definitely have to trust my horse not to take off before I would hook him up to a cart.
My friend shows her ponysin carting and when she was at a pinto show the minis and ponies were in the same class with the big horses. I would never do that too much of a risk but anyways there was a horse that had only been hooked to the cart once and it was only his seconed time and they were showing him Then he freaked out and took off and people were trying to catch him and two people ended up getting hurt. One broke her leg and I think she was the one driving the cart with the horse that freaked out. I just didnt see the comon sense in putting a horse that has only been hooked to a cart once and putting them in a horse show which could potentially danger other people.