A quick Google search will show pics of the poor dead horses in such crashes. And the buggy occupants fared about as well, I'm sure.
I've spent years driving in Amish country in PA and OH -- simple safety reflectors and lights are not a lot to ask.
Do they use any kind of lighting back there at all, candle lanterns or anything on the rear?
I live on the edge of Amish country, and yes, wrecks like these are all to common.
Sunday afternoons are particularly deadly because you have more Amish on the roads either returning from church or courting plus an influx of motorists from places unaccustomed to needing to beware of buggies.