> It is feasible to know everyone's destination station at the time of boarding.

I challenge you to find a mechanism that works for this and is quick enough to keep up at rush hour in the average Tokyo train station.

Additionally, people move at different speeds through the station due to factors like age, familiarity with the network, disability, bladder capacity etc.

It’s a non-trivial problem to solve, and likely only marginally improves user experience.

Put an electronic sign up on each station platform indicating where the cars with most space will be on the next train. Some people will rush to those cars, some will just stay where they were. By varying the amount of notice given or the threshold where you consider a car "less full", you can distribute the travellers more evenly.

I suspect the reason this isn't valuable is that the feedback loop is already pretty good at high occupancy rates: when one car is at capacity, every other car is too.

You can indicate your destination at the entry turnstile to the platform and it will tell you two things: (a) the car you should board, and (b) the car you should exit from at the destination station. Most times, (a) and (b) are same. Some times, (a) and (b) can be different – say when you have more cars than then length of the platform supports, then some cars will hang off the platform length and hence their doors won't open. If you were assigned to board such a car, you have to make way to another nearby assigned car whose door can open, which is assigned to you so that everyone won't crowd the same last car aligned to the platform.

Have you never been in a metro train before? There's not actually that much seating, if you only had people sitting down that'd be like a tenth of the train's capacity.

Not to mention the trains stop every minute or two, and people don't, like, book that stuff ahead of time.

I guess you took my "assigned seating" literally. I obviously didn't mean _seating_ but more of an assigned spot in a train car. The point of an assigned spot is that there can be different designated areas for different people – elderly, women, kids, disabled, those with cycles, those with luggage, general etc. and now with Covid19, these assigned spot density could be appropriately adjusted.

I still don't see how that would help. What does adjusted mean? The problem is there isn't enough capacity, yeah they could just reduce how many people can take the train, that means people being late to work or otherwise with an impacted schedule.

And they already know which train routes at which times are crowded, if they could just add more capacity they'd have already done it.

Most stations already have posters telling you:

- which cars are normally less crowded

- which cars are recommended for getting off at a certain station, based on proximity of the exits at that station to each car

Google Maps (as well as other apps) also show similar information when asking for transit directions (for the former it only gives you the average on the whole train, not by car)