Robert has got the part that needs fixing. Martingale is way too loose, letting collars be pulled forward. The Quarter strap/belly strap, from breeching end to martingale, is too tight, making the breeching tight all the time. Maybe photo shows sleigh pushing the animals, but still the martingale should be tight in the picture.
Enlarging the picture just shows the middle part, not pole details or rear of animals.
The martingale and quarterstraps are part of the whole harness system, so they both need to be snug, but not tight. When pressure is on one, the other helps hold it, spreading the force over the horse body.
Breeching is just regular breeching for a Draft Pair. Yankee breeching has the strap ONLY across the top of rump in front of the crupper. Breeching ends fasten to the ends of martingale at girth. There is NOTHING in strap work below the tail crupper on lower haunches. All the pull of Yankee breeching from the martingale-collar-neck yoke, is then on the top of rump, pushing horse down. No chance of sweeping his legs out from under him with a push from load behind him.
Neck YOKE on the dropped pole is going to be rather low, compared to the CDE style YOKE on a sprung pole, because dropped pole hangs from the bottom of yoke ring. Dropped pole yoke is held up by the horses, weight is on the neck all the time.
A yolk is in an egg, not on a vehicle.
The metal yoke appears to have a safety rope to prevent it coming off the pole end. Usually the pole end is much longer beyond the yoke ring, for safety. A safety strap, rope, something, is always recommended on a drop pole, to hold the yoke on pole, if straps or pull of load removes tension between pole strap/snaps, traces and vehicle.
If the yoke ring comes off, the pole will drop to the ground, often stab into the dirt. Horses are still pulling, so problems result, with vehicle usually tipping over.
Everyone has “their way” of doing things in driving. However I feel compelled to point out that snaps on the reins are a bad choice. Folks tend to just snap stuff together, not really look as they hitch. Snaps shown are not very strong, just cast white metal with light metal for the clip part. Personally, my dog has broken a few of these snaps when tied, and the clip part rusts very fast if it gets wet or sweaty. I would NOT want to trust such snaps with the rein control of my horses.
Part of the snap use problem is the fact that person hitching, NEVER looks at the rein billet fold holding snaps on. Rein billets tend to collect a lot of dirt, moisture, which makes the rein material get extra wear, stitching often is rubbed away. Just too easy to clip and go, not check your harness and parts.
If you buckle on your reins and breeching straps each hitching, you should notice wear, dirt while handling straps. Then you can take steps to change worn equipment before it is dangerous or breaks just when you need some strength.
Still on the reins, they look twisted. Reins for a Pair should be smoothed flat forward from the coupler, so they are the same length, or correct adjustment to equalize the horses. A twist or two will shorten the one rein, affecting how the horse goes, and maybe make him act badly that day. Twist might hang up in a rein terret or hames ring, grab your horse on one side with no release. The pull of reins from driver is never going to work evenly on both horses as the reins are designed to do. Adjusting the coupler won’t help either.
You can get away with some stuff sometimes. Then it will come back and bite you when you least is expect it. There are reasons that accidents happen, which we all want to prevent.
