The best transfer station I’ve seen was when visiting Taipei.
They used large diameter boring machines for some of the lines, which allowed for putting opposite directions on top of each other, rather than the standard next to each other configuration.
So at a junction, you would have four tracks inside of one tube, and the other line be right across when the train stops. Now they sync the two different lines to always arrive simultaneously. Thus a transfer is you go out of one train, and right there, across is your connecting train.
I’m not sure how much the whole thing cost to implement and maintain, but I do think it was all worth it. It allowed them to have really accurate and fast travel times across all the lines connected this way.
London's Victoria line was built for "cross-platform interchange" like that (often by having its lines arrive on the "outside" of another line, so that both tracks were alongside same-direction tracks). Nowadays it's something they generally avoid, on the grounds that it reduces circulation space - with the system running close to capacity, they prefer to have everyone walk further so that the crowds spread out a bit.
That would be great if feasible, but I think most transfer stations have lines crossing each other at near 90° for obvious reasons, which would make this impossible.
I’m in Taipei now, not every intersection looks like this. But I remember seeing it at Chiang-Kai Shek Memorial Hall station (https://en.wikipedia.org/wiki/Chiang_Kai-shek_Memorial_Hall_...). On the Taipei MRT map you’ll see that both the red and green lines make a change in their trajectory here, allowing them to go parallel.
I think the technique the OP described is “necessary, but not sufficient” for these types of transfers.
I think most of these stations are on networks that had a coherent planning that was followed through from the beginning - like in Munich, where the U-Bahn network started to be built in the 1960s (late compared to Berlin and Hamburg) and was continuously under construction, mostly following the original plan, until 2010. Munich has two of these cross-platform transfer stations, Scheidplatz and Innsbrucker Ring. Both of them were built with 4 tracks from the beginning and had to wait several years (or even decades) until the cross-platform transfer concept was actually fully used with two lines coming from different directions and also continuing in different directions. There are two more four-track stations (Münchner Freiheit and Olympiazentrum) which will probably never be used as cross-platform transfer stations - I think at Olympiazentrum the additional tracks were intended to increase capacity for large events (football matches, concerts etc.).
Well, that's only going to work if there's enough underground space for railways to turn 45° before entering the station. Judging from what I've seen, most "important" transfer stations are in an urban district where railroads follow existing roads, so curving them would send the lines underneath existing buildings, making it more expensive and also slower (trains don't like to turn, after all).
Somewhat tangent, but reading through this, on top of everything else, I really admire this type of dedication. I’ve been slowly walking through every street in my city for fun, just to have it visualized on a map, which is incredibly easy compared to what this person has done. Nothing but deep respect, and it makes me appreciate the public transport even more.
> For the last 10 years I have been able to draw around 1.517 stations from different European cities, motivated by the curiosity of understanding how engineers were able to fit underground stations comprising 4 or 5 lines under Place de la République in Paris or the Puerta del Sol in Madrid.
> A pen, a notebook, a bit of spatial vision and the willingness to navigate all the staircases, corridors, platforms and mezzanines are enough […]
The Tokyo metro stations are amazing. A diagram on the screen of the exit doors showing the locations of lifts, escalators and exits along with numbered/lettered exits. Google maps will properly direct you to the correct exit point and the station way-finding is exemplary.
I find it exquisite that Paral·lel station in Barcelona really has a parallel platform layout (despite the station name deriving instead from the fact that the street with that name is parallel to the equator). https://en.wikipedia.org/wiki/Avinguda_del_Paral%C2%B7lel
They used large diameter boring machines for some of the lines, which allowed for putting opposite directions on top of each other, rather than the standard next to each other configuration.
So at a junction, you would have four tracks inside of one tube, and the other line be right across when the train stops. Now they sync the two different lines to always arrive simultaneously. Thus a transfer is you go out of one train, and right there, across is your connecting train.
I’m not sure how much the whole thing cost to implement and maintain, but I do think it was all worth it. It allowed them to have really accurate and fast travel times across all the lines connected this way.