I advise all saddlechariot users to wear a safety helmet.
I know there are numerous pictures of me and my family not using safety helmets, but I can only quote Vivian Stanshall of the Bonzo Dog Doo Dah Band; "I never practice what I preach beacuse I'm not the sort of person I preach to."
I have had numerous accidents and near misses, almost all caused by the pony/horse/whatever doing something unexpected. A helmet reduces the risk of head injuries dramatically and is a sensible precaution which I strongly recommend.
I do not fit reflectors to the saddlechariot. I believe they are a legal requirement for a road going equestrian vehicle, but fitting them might imply I thought Britain's roads a safe environment for animals, adults or children. Look at the number of animal bodies along the stretch of road you intend to drive and assess whether it is a safe environment for animals. Look at this nations children, driven everywhere or stuffed in front of a TV and ask whether the roads are safe for children. If you do decide to go on the roads, a couple of reflectors are not going to make you safe, it only means you die legal.
The mudguards are designed to allow the fitting of most types of bicycle lights. Flashing lights are more effective and are, I believe, illegal, for this reason. Personally I don't think anything less subtle than a Kalashnikov will get through to most car drivers, but I find a roadmenders yellow reflective jacket is easy to confuse with a speed cop's and is consequently quite an asset.
Henry, my 10.1hh, Shetland X is tiny, sweet and cuddly and the same size, weight and strength as an adult male gorilla. You are driving a very powerful animal, for whom flight is the instinctive reaction. Learn to read your pony and remember the first rule of saddlechariots: IF YOU ARE WORRIED, STEP OFF, REMOVING THE SADDLECHARIOT FROM THE PONY.
This leaves you, at worst, with a loose pony, roughly what you have if you fall off when riding.