I used to regularly use these at the Uni of Leeds in the Roger Stevens lecture theatre building. Never saw an accident. Freshers were told that they turned upside down when going over the top but in fact they just slid sideways to the next shaft (we used to ride over the top sometimes to beat a queue going down) but they could apparently jam if too many people tried it so it was frowned upon by the porters.

Got to ride one of those in the Bat'a building in Zlin, Czech Republic. Supposedly that version had some sort of safety mechanism to keep you from crushing your arm off if you didn't have it tucked inside, but I didn't dare test it. We called it a "Mario elevator" due to the obvious similarities with the elevators in the original Super Mario Bros.

"Their overall rate of accidents is estimated as 30 times higher than conventional elevators. A representative of the Union of Technical Inspection Associations stated that Germany saw an average of one death per year due to paternosters..."

Wow - those were definitely different times in terms of acceptable risks in various aspects of life.

Modern times obviously improved a lot of it, but if you're at least a bit cynical, you also have to wonder how much, due to those measures, people are "prevented" from having to build out their awareness of surroundings, dexterity and overall "aptitude for life".

It's like they took an obstacle from some Mega Man stage and implemented it in real life.