[Q&A]: Why steps at most of newly built Delhi Metro Stations kept rough & unpolished?

Ms. Stella Jose, one of our recently added subscriber, asked through bricks-n-mortar's twitter handle #bricksnmortar:

"Hi! Appreciate your blog post about Delhi Metro depicting some of the genuine problems we the people face on a day today basis. It truly lists out the shortfalls that Delhi Metro should attend to to make traveling by Delhi Metro a real pleasure that it used to be till recent past.

I have a another question sort of related to Delhi Metro. I usually take the stairs instead of the elevators and escalators at the Metro stations. One thing that I observed there intrigues me daily, which I would like to ask you...

Why are some portions of the stairs kept very rough and have not been polished?

My architect friend told me that the steps being of marble or granite are polished once all of them are laid in pattern. But one day I saw some people actually removing the polish after which the stairs have become rough and sort of uglier. Can you explain why?"
Delhi Metro Station - Stairs & Escalators

Efficient Network of Stairs & Escalators @ Delhi Metro Station

Team bricks-n-mortar answers:

Dear Ms. Jose,
Foremost, we appreciate your observation power. You've pointed out which even many qualified professionals won't generally notice and raise a doubt on.

Coming back to your query, your architect friend's point is right that finishing stones like marble, granite, sandstones, etc. are first laid in place as per the desired pattern on horizontal / vertical / inclined / special surfaces like floors, wall claddings, stair risers and treads, facades, skirtings, domes, curved surfaces, etc., and then finally ground with hand buffing machines and/or mechanized grinding & polishing machines. The rough to semi-rough surfaces are polished to provide a smooth and near-mirror finish.

Such fine polished surfaces, though are desirable at homes, offices, hotels, restaurants and other such hospitality related places, are not desired in mass public commuting places for the simple reason that no one should slip over and hurt himself/herself.

The finished surfaces of such public places are therefore kept semi-smooth only thereby keeping certain amounts of friction playing active role when mass transit of people happen at a certain place at any given point of time.

In case of Delhi Metro, that you have correctly pointed out, the surfaces were initially wrongly fully polished at stairs of many a metro stations (tube stopovers). It must have been pointed out by the technical personnel whereby the wrongly fully-polished surfaces were roughened up to certain extent to provide helpful frictional advantage.

Hope this suffices to your query. Keep posting and commenting :-)  Reproducing a few pictures of Delhi Metro to let you visually understand too.

Delhi Metro Platform

While most of the boarding platform is well-polished, the end
embarking stone is kept unpolished to avoid accidental slippage

Delhi Metro platform - Fully polished granite surfaces

Most of the platform is kept fully polished

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