It is interesting, the first thing I thought of Frank, was the stability. I can't imagine peak hour or a natural disaster nearby or a terrorist one. Then again if public transport was better all around the world would we need such structures. Also I was in a lift, in the Brisbane City Hall, in the early 70's when a guy was caught and the lift started to move off to another floor & there wasn't much technology then to stop it. Between a couple of us we managed to free him within a couple of feet of movement while all others were in shock. I'm sure many others have witnessed similar.
Ranald