That "green + green = black and blue" thing applies to two horses in a pair as well.
With draft horses a youngster is almost always started in a pair because the older, wiser horse will not only settle down the youngster, he or she is quite capable of essentially holding the green horse back if he tries to do something stupid like bolt!
They have the temperaments to stay calm when another horse is acting up and listen to the driver.
With light horse breeds of good temperament, a young horse might be put to a pair after they've learned their basic job as a single to gain more miles with an experienced horse who can show them there's nothing to fear in the big world. There's video on YouTube of Diane Kastama taking her younger Welsh Cob to the beach as a pair with her older competition horse and wisely positioning the two horses so the older horse held the younger one steady when it wanted to spook at the waves rolling in. This is a fine idea and a good way for an experienced whip to season a horse.
But putting two green horses together in a pair with a green driver handling them is, in my opinion, asking for trouble even with professional guidance. Now an experienced pair driver might be able to put each mare one-at-a-time in a pair with an experienced animal and THEN put the two together, but I would not have their first experience in pair driving be with each other as if one horse spooks, the other one has no experience to understand what's going on and is likely to become infected with the other horse's fear and escalate the situation. That's a recipe for runaway!
I've been present when two experienced single driving horses were put together for the first time and that was nerve-wracking enough when they both got upset for a minute.
Having an experienced driver was critical in that situation as we were able to give the horses confidence and knew how to handle the situation so it never got out of hand. If the driver had hesitated or done the wrong thing it could have gone south very quickly.
Get some lessons driving a pair so you know how to start them together, how to stop them smoothly, how to handle turns and circles and backing. Learn to adjust the equipment correctly so both horses are comfortable and can do their jobs safely. Make sure each individual horse is solid as a single and can be trusted in any situation. Then find an experienced pair horse to partner them each with for at least one quick drive under your trainer's supervision and then you can consider hitching them as a pair together.
Pair driving is a LOT of fun and in some ways easier than driving a single, but you need to know that each horse will respond without fail to individual voice commands and will WHOA when told, no matter what the other horse is doing.
Leia
