[spiralx]

The Victoria Line in London runs at 36 trains per hour at peak, one every 100 seconds. Station dwell times are already a limiting factor at this point, and having separate load/unload platforms would provide only a small decrease in dwell time as you'd need to open the unload doors before the loading doors to prevent people just exiting the wrong side.

[Retric]

You can have multiple platforms and send trains to each not just separate load/unload platforms. This was very common with passenger trains as boarding times could extend for long periods. Even when it was a single line for loading and unloading they would normally have a bypass line to avoid the station.

[spiralx]

> You can have multiple platforms and send trains to each not just separate load/unload platforms.

Sure, but we're talking about subway networks underneath major metropolises, and adding extra tunnels and platforms is basically as expensive as digging a whole new line - when it is even possible due to space or geological constraints.