Intelligent stairs - can it be done?

Intelligent stairs - can it be done?

Yesterday I wrote about local intelligence and the possibilities doors have in this respect. Today, reading yesterday's note, my mind turned to stairs - another building element that fascinates me. Why do I expect intelligence from doors and not from stairs? Why do I assume that stairs are to remain passive or even unyielding? Is it just that I'm used to dynamic behaviour in doors? There are automatic stairs, too; escalators that detect that someone is approaching and start rolling. Why does this impress me less than a door automatically opening to admit authorised persons on a biometric basis? Could it be so that I see stairs as a danger, something to be feared and treated with caution - and for that reason prefer them to be passive? 

It could be because intelligence in stairs may be far more demanding than in doors. Automatically adjusting the stair dimensions to the size and mobility of every user would certainly impress me but it wouldn't be easy to achieve, even if it were about a single user at a time. Stairs that could accommodate several users simultaneously in this manner would be a feat worthy of the highest praise for its ingenuity but, as societal or technological priorities go, not of the same order as a cure for any persistent illness. So, I fear that stairs are to remain relatively unintelligent, passive and a bit menacing - beautiful but rather dangerous.