One fine evening heading out after a day’s work, I was at the MRT station (that’s what they call trains or subways in Singapore) heading somewhere and a woman behind me proclaimed loudly in an irritated manner, “Why don’t they have 2 escalators going up instead?”
I’m sure everyone noticed this at Clementi MRT station with 3 escalators that 2 escalators are always going down in the evenings (I’m not too sure about mornings), and 1 is going up. Many have complained many times while going up the escalator that the other 2 escalators going down are empty. Just to give some context, 2 escalators are going downwards to the exit of the station, and 1 escalator going upwards to the platform.
Here is the rationale of why it might have been done this way, instead of 2 escalators going upwards to the platform.
Logically speaking, you do not want to your platform to be filled with people. If you have 2 escalators going up, that means for every 4 people going up, 2 people are going down (hypothetically speaking), assuming 2 people can get onto the platform per escalator. If you do the math with a normal constant distribution across a period of time, your platform will eventually get filled up. However, this is not a normal distribution, because we have to take in account the number of people getting on the train and off the train.
Assuming that every time a train comes, the number of people exiting the train into the platform is lesser than the number of people entering the train. This means the replacement rate is lesser and less people are exiting. It does not make sense to have 2 escalators going downwards. However, during the evenings after work, since Clementi is a heartland, i.e. residential area, we can assume that the number of people exiting the train will be more than the number of people entering the trains. Therefore it make sense to have 2 escalators going downwards to allow these people to exit.
Does that mean that in the morning while people boarding the trains at this station will be more than the people exiting the trains? Does that justify the 2 escalators going downwards? Since I do not take the train in the mornings, I cannot comment on the current situation. However, it still make sense to have 2 escalators going downwards to channel more people to exit the station.
Do you want to take the risk of overcrowding your train platform if you were in charge of the station? No. How about if there is a sudden influx of passengers into the station from the trains, which happens every 1 minute or so during peak hours? You need to channel them out of the station quickly. So it only makes sense that the station is designed to prefer channelling more people out of the station rather than into the station.
That, is why MRT stations don’t have 2 escalators going up instead.