Comment by tazjin
1 day ago
Moscow has been integrating many of the commuter rail lines that run to various train stations in the city into essentially the metro network.
This means building new stations, connecting them to existing metro stations where possible, unifying the payment system, upgrading trains and so on. Since 2019 five lines like this that all run overground have been opened: https://ru.m.wikipedia.org/wiki/%D0%9C%D0%BE%D1%81%D0%BA%D0%...
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You can see how they connect to the larger metro network on the general metro map: https://www.mosmetro.ru/metro-map
There have been a few similar projects, like reporpusing an unused underground rail cargo tunnel network as another metro line (the turquoise ring around the centre in the map).
In much smaller cities like London or Paris you could probably also find some more lines like this and integrate them, but it needs the political will of course.
The metro systems in London and Paris extend outside the areas strictly defined as those cities, the populations served are only slightly smaller than that of Moscow.
Of course they do in Moscow too, the metropolitan/commuter areas exist in most big cities. Seems to be about 8 million less than Moscow for Paris, 6 million less for London, based on what Wikipedia currently says about the respective metropolitan areas.
For what it's worth, I lived in London for some time and its commuter rail system is much less integrated and much more confusing (with different companies, incompatible tickets and so on). In the city it's fine, though the tube isn't very comfortable (except for, ironically, its oldest lines which have luxuries such as ventilation).
> with different companies, incompatible tickets and so on
They have all been using the same tickets for a while now, and of course it has been all Oyster for more than a decade as well. I’ve been commuting using Thameslink or Southeastern without trouble for about as long.