PowerSwitch

Not for myself.
A neighbour uses a horse drawn cart or wagon regularly on public roads. Effective lighting is clearly vital after dark or in bad weather. The present lights, fitted by myself are reasonable but could be better.

Two rear lights are fitted, one each side. They are intended as dynamo powered lights for cycles, each is fitted with a 1 watt red LED bulb, the light is impressive and better than the 5 watt incandescent tail lights fitted to most cars.

Four front lights are also fitted, two each side. These are also cycle type lights each fitted with a 1 watt LED bulb. Once correctly adjusted these give an excellent forward light on straight roads. One headlight each side gives a well focused beam that lights the road some distance ahead, the other light gives a broad floodlight. All lights are lit normally. When passing another vehicle, the narrow beam headlights may be extinguished by a hand held switch. (on a trailing lead such that the reins may be held at the same time)

All 6 lights are powered by a 6 volt sealed lead acid battery, run time about 12 hours. "Bardic" handlamps as used on the railway are carried as spares.

The front lights suffer from two drawbacks, firstly when cornering, the body of the horse casts shadows which reduces the light and may spook the animal.
Secondly even on a straight road, the horse casts moving shadows due to the lights being behind the animal. The usual horse seems used to this, but a borrowed animal took fright and could not be safely used.
A light attached to the helmet of the driver gives a rather poor light, that moves in a perhaps horse spooking way as the driver moves their head.

Horses have good night vision, the lights are mainly to warn other road users and not for the horse to see its way.

I recall when I was at university in the US there were Amish living nearby and note that the carriages had to have a red triangle on the back. Not sure about lights but I only saw them during the daytime.

Maybe the 'visibility' front lights should be heavily diffused and 'soft' lights.

The 'beam' front lights should be positioned as low as possible so that only the feet of the horse disrupt the beam and having several of them either side of the horse could negate the effect of shadows caused by the horse movement. Or put it on the lower side of the horse's collar.

Part of the problem was the horse being rather nervous especially after dark.
A new horse seems more placid and reliable and seems happy, it is also larger and stronger than the old one. The new horse always seems hungry and looking for grazing or prepared horse food. Vet states that it is overweight.

The old horse is now only only used for riding by the kids.

The new horse can be spooked by cyclists, I think that it finds the silent progress unnerving as is not worried by motor vehicles or other horses.

When I rode recumbent bicycles horses regularly got spooked. WIth the pedals out in front, and my feet going up and down on them, I looked a lot like a predator animal galloping straight towards the horse and the horse's survival instinct takes over.

Update, the problem was the horse and not the lights.
Not only is the new horse fine, but a second newly purchased horse has also been used after dark without issues. Both are liable to be spooked by cyclists but are fine with motor vehicles and other animals.