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Comment by asdff | Hacker News Reader

A mezzanine level is expensive and only serves to delay people. It doesn't get more people into more trains. Only more frequent and longer trains can do that, and that is dependent on the length of the platform and how many trains can move through a given tunnel an hour, the mezzanine is extraneous. It makes people not want to take the train by introducing bottlenecks by making you go through another set of stairs or escalator. But I'm sure the expenses associated with the mezzanine lines a bunch of people's pockets, so I wouldn't expect sensible design to come into fold anytime soon in our contractor-graft based country.

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In London (where I commute), without 'mezzanine levels' or their equivalent, there's nowhere to queue and everyone would squeeze onto the platform which is a safety issue and then the police and/or the railway staff would close the station. This happens frequently when we have problems with the track or trains.

London has terminus stations - the platform the train arrives on is where the train stops, and then starts on its return journey. Trains to your destination are therefore limited by signalling and traffic, typically a 10-15 minute turn around time. On average, in London during rush hour, you have a train to your home station every 20 minutes.

Perhaps in the US all major stations are through stations, but in the UK, especially London, we just don't have that, and mezzanines are at the very minimum, a safety requirement, because the platform your train leaves from, has other passengers waiting for other trains before your one.

Platforms are not large, and trains are very, very busy, and frankly, if you've only ever caught a train in the US you are in for a huge surprise commuting in the UK.

If the US ever adopted trains like the rest of the world has, the best time for building mezzanines, and huge stations is "yesterday".

You're comparing regional rail terminal stations, which serve many lower-frequency lines, to subway platforms, which typically serve a single higher-frequency line. (2-10 minutes between trains.) That's the scenario where a mezzanine is less useful.

Don't get me wrong, people do take the train in LA. The red line before the pandemic was packed full of people during my morning commute, transporting 130,000 people a day. Standing room only for the entire subway train. That being said, you'd never have people waiting on the mezzanines at these stations. The platform is already big enough to hold like 3-4 trains worth of people, and a train comes every 10 mins (every 5 mins where the line is staggered with another subway line downtown) and it is cleared out of people waiting when the train comes (sardines squeeze well).

To expand capacity beyond that would require reengineering the tunnels themselves. They go as fast as they can turn around and vent air as it is. You'd have to bore parallel tunnels to increase capacity, which would just mean adding more platforms and still wouldn't require a mezzanine.

130k/day is not that much, Stockholm's tunnelbana has 3 main lines: red, green and blue, in total they support 1.1 million passengers/day with the current expansion of the blue line planning to add another 170k/day.

This in a city of around 2 million inhabitants for the whole metropolitan area, which is also served by busses, trams, local trains, ferries and so on.

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