Every time you approach the subway, the first thing that meets you is a huge heavy door dangling in both directions. The weight of the door feels good, but opening it is not difficult for most people, including children. The question arises: why do we need such massive doors and wouldn’t it be better to put something lighter?
It is quite obvious that the massive doors at the entrance to the subway are not installed at all in order to help citizens gain muscle mass. In fact, the reason for installing heavy doors at the entrance to the subway is purely technical and is related to the peculiarities of the operation of this type of transport. Interestingly, when the metro appeared, the weight of the entrance doors could reach 100-120 kg. However, even then the doors opened relatively easily due to an ingenious system of hinges. Modern doors weigh almost 1.5 times less.
Why are they needed? It's simple: heavy doors help to ensure normal air circulation in the subway, which is violated by electric trains every now and then. Since the trains move at high speed, they also set the air around them in motion. If there were no doors at the stations, in principle, terrible drafts would go all over the metro. If you hang light doors on the entrances, then the dispersed air mass will easily hang them on hinges from side to side with each passage of the train, which, firstly, will not solve the problem of drafts, and secondly, creates an additional traumatic precedent for passengers.
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It is noteworthy that in a number of cities the doors of the last century are still hanging at the entrance to the metro. They are preserved solely for aesthetic, cultural reasons. At the same time, one should not think that they are not removed at all. In fact, the heavy doors of subway stations are regularly serviced, replaced or restored. First of all, you have to change the hinges, which provide a relatively easy opening for a person.
If you want to know even more interesting things, then you should read about why on the roofs of houses of the Stalin era were built mysterious tower houses.
Source: https://novate.ru/blogs/140322/62411/