The one at my old uni used to sort of move sideways once it got to the top/bottom, then moved up/down as appropriate. Needless to say, there was a lot of pratting about associated with them - people who didn't like the dark bit being forced to stay all the way round, etc, maybe that's what happened to that poor girl who was killed. It was quite safe as long as you acted sensibly, but then that applies to most things.
I agree with what people have been saying about the nannying of idiots. If there's a warning sign - 'Danger 10,000 Volts' and some idiot ignores it, that should be his problem, not a matter for litigation. The youngsters nowadays . . .
Oops, I've just fallen off me soap box!
Carole