The main reason for blinders is to prevent the horse anticipating thing by reading your body language. If you follow any kind of routine (recommended for safety reasons), the horse quickly learns it and may want to “help” you. Like you move the whip which should always be in your hand, he thinks you mean to touch him for Go. Not true, you wanted to brush off a fly! Or people get in cart, he walks off " because they ARE in" but not seated yet! Horses are huge on reading body language, keeps them safe in the herd. Unfortunately horse guessing your next move or choice of direction, speed, may be incorrect choices, so bad things happen before you can stop them.
We train in open bridles, horses have seen scary vehicles, dragging things following, not afraid of them. They graduate to blinders as their training advances. The blinders keep them focused FORWARD, not sight seeing, anticipating things they see around or behind them. Horses WAIT for directions. They do not get to choose what is next.
There cannot be two “Captains of the ship” in driving. Horse does NOT get a vote in decisions. They just need to follow directions.
Many folks count on horse following routines, it works in their situation, like farmers. They usually work horses in limited locations, do repetitive things and try to save themselves steps in daily life… You do see them using open bridles at times. Many times their methods work fine, other times bad things happen because horses made poor choices by breaking their expected routines. Horses thinking independently is a very bad thing while driving because of attached vehicles… Like a driverless car in gear, they are hugely destructive going forward randomly…
Have you seen this trainers finished horses driving? How long does it take them to prepare a horse to be hitched and driven? Do they start the new horse as a single or put it in a Pair to begin driving it? How long are the training sessions? All things to consider. We do a LOT of ground work instilling commands, building “a working relationship” with each horse, to make sure horse completely understands what we are asking him to do, has confidence in us. He learns trust in us, is willing to do weird or odd requests because we ask.
There is a lot to starting a driving horse, so ask questions, read books like Doris Ganton, “Training The Driving Horse”. Clear photos, steps to follow in training, fitting harness, carts to your horse. Vehicle you want to drive should be safe, checked for good bolts, solid wheels and shafts, not weigh a ton for beginner horse. Heavy load or vehicle scares them until they learn they CAN move it!
And if your horse likes a wide view, there are various style blinders beyond the basic square models fitted snugly over their eyes. These other model might take a bit of looking to find, but are out there. We have two at my place that wear half-cup blinkers, while the others all wear standard blinkers Those two just lIke more view forward, but still can’t see behind or a lot to the sides.
Welcome to this group, and driving!