To my mind something is 'dangerous' if normal behaviour from a normal group of people exposed to the risk has a reasonable chance of leading to an accident.
Two examples:
Coiled Kettle Leads were introduced due to a significant number of those exposed to the risk of tipping boiling water down themselves being in the habit of grabbing things that trail down from the worktop above them. Not all children were exposed but a significant number of parents weren't 'on the ball' 100% of the time so a non-trivial number of children were scalded, like a chap I knew in college who was nearly killed at the age of four and had massive scaring down most of his right side.
In theory drivers and pedestrians should be aware enough that zebra and other types of crossing are superfluous.
Remember that the 'not dangerous if everyone is on the ball and aware' was used by the early railway companies to argue against signalling. In their book it was always the drivers fault if a collision occurred. After that it was always the signallers fault - no matter if they were working 7 days of 12 hour shifts - if they had just been more aware then collisions would never occur, there is no need to introduce interlocking and limited hours of work. Its a shame about those who are incidental casualties...
Fast forward to Slam Doors. As a regular commuter who was fairly aware of the risks the biggest risk to me was a door in the face from the person getting off in front of me, who would randomly slam the door shut behind them as we were getting off. I got a couple of big thumps, one that left bruising, as a result. I could have hung back, of course, but there were people behind me and what would it have done to station dwell times?
On the 'wrong side opening' issue. Yes, you might argue that people should be more aware and only travel when well rested, sleeping under their desks if they have had a long day at work and therefore aren't in a fit state to operate dangerous machinery, but people will insist on getting home to family and friends... Its a shame about the people who have to clear up and the driver who has just had a door through the front of his cab...
Similarly, surely there was no need to add the supplementary locks to the HST sets? It wasn't dangerous if people didn't lean on the doors, they should have known not to board a train at crush capacity or travel in the vestibule, just 'asking for it'...
And of course there was never any good reason to add yellow lines to platforms, a disproportionate expense, people should know instinctively what is a safe distance. Its a shocking waste of money, just like barriers at Level Crossings.
Bottom line - safety has to live in the real world where people make mistakes and there are innocent victims of mistakes made by others.
