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Comment by fivea | Hacker News Reader

> When you have someone deliberately setting fires and blocking the escape routes with a knife, you have bigger problems than just one stairwell.

The software world is well versed in the concept of a single point of failure, and the importance of eliminating it and mitigating any chance.

And yet here we are downplaying a critical design problem because it was a single point of failure?

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As always, you have to balance the risk of a crazy trap-setting knifeman attack with the (opportunity) cost of building additional escape routes.

Not just the risk of a crazy trap-setting knifeman attack, but the risk of other things that are likely to block a single exit (as fire sometimes does.)

Yes, but it looks like that sort of events (where additionally you have to evacuate rather than shelter inside your apartment) seem to be exceedingly rare, given that lack of a second stairwell has not been a problem at all in several Western countries.

> As always, you have to balance the risk of a crazy trap-setting knifeman attack with the (opportunity) cost of building additional escape routes.

A "crazy trap-setting knifeman attack" is not the only scenario that results in a blocked exit trapping people inside the building in a life-threatening situation. Think about it for a second. Imagine, for instance, that a fire breaks out for any reason. Is this unthinkable? And how do you factor in emergency response personnel trying to go up the same stairs that are the only way out of people trapped in the building?

We should not forget past lessons for no reason.

Yes, but as the article pointed out - building fires are no more deadly in countries that allow single staircase construction. I suspect that in reality it's simply an incredible rare occurance that not only you must evacuate(rather than stay put in your flat behind fireproof door), but also that the stairs are blocked, AND the fire brigade cannot clear them out AND the fire brigade cannot get you out any other way.

Yes, past lessons should be remembered but it looks like there is no data that would support building double staircases in reality - it's just too rare of a problem. Same reason why almost nowhere in the world requires outside fire exits like many buildings in NYC do - they are great in idea and I'm sure there are examples of them saving lives, but it's not worth making them a requirement for every building ever made.

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