Lots of reasons for - and some against. Someone must have thought they were necessary - after all, it's an extra piece of work for the harness maker and extra $$ for the buyer, right?

Many horses driven single can cope with seeing "everything" and some are calmer if they can do so. I've had several Fell ponies who were trained in open bridles and are equally happy with or without blinkers (winkers/blinders). I had one mare who was trained open, and got jittery if she was harnessed with blinkers; though after 5 years of steady work she didn't mind them if we were showing or doing a wedding with a smart harness that had blinkers.

Some military teams (4 or 6 up) drive without blinkers, such as the Royal Horse Artillery in Britain. But these use postillion riders and are not driven from a box on the carriage with long reins or with a long driving whip - both of which demand eye protection for the wheelers where the leader reins pass the head.

Then there are animals who get distracted or worried, and for them a half cup or full cup blinker is helpful. You can turn their heads away from scary objects and the object effectively "is not there" because it is hidden by the blinker. I've had a couple (one hot, one not) who were much more relaxed when wearing blinkers. Sounds stupid but it's true.

So - it's partly local fashion or tradition, and partly to do with the temperament of individual horses, and partly the nature of the job they are doing, that dictates whether a horse goes in blinkers or an open bridle. If you are not showing or going to any fashionable meets, it may not matter which you choose, except to you and your horse. But exercise caution...

The safest way is to have your animal trained without blinkers first, then repeat the training with blinkers if necessary. The frequent remark that blinkers "hide the wheels" from a horse is a bit of a red herring IMO - any horse in harness who doesn't know he is pulling a carriage/cart is really stupid, or has been constantly tied up in side checks - because he only has to turn his head round as yours does, to see the object. And I'd rather not drive a horse who would be frightened of seeing the carriage, but that may be just me.

If you think your horse sounds like a good candidate for trying without blinkers - do some work on the ground in the open bridle without the cart, and go through some training steps, like dragging a tyre or log, and having a friend bring the cart up behind and letting him see it follow him as he walks. NEVER just replace a blinker bridle with an open one and expect a horse to behave the same when hitched - many have not been trained without the blinkers and there's always the chance that those will run.

Keep us posted if you decide to try it!