Which is why in such populated areas there should be at least 4 tracks on a major route: 1 in each direction for local and regional trains (like S bahn in Germany, RER around Paris etc) and 1 in each direction for higher speed intercity or better (like ICE in Germany, TGV in France)… They don’t necessarily have to follow the exact same route, the idea just being there should be fast non-stop options between big agglomerations AND slower stops a lot options to fill the gaps the fast trains leave.
Or at the very least 4 tracks at certain points to make it possible to combine local and long distance on the same tracks but with the option of the long distance one overtaking the local one…
Which is why in such populated areas there should be at least 4 tracks on a major route: 1 in each direction for local and regional trains (like S bahn in Germany, RER around Paris etc) and 1 in each direction for higher speed intercity or better (like ICE in Germany, TGV in France)… They don’t necessarily have to follow the exact same route, the idea just being there should be fast non-stop options between big agglomerations AND slower stops a lot options to fill the gaps the fast trains leave.
Or at the very least 4 tracks at certain points to make it possible to combine local and long distance on the same tracks but with the option of the long distance one overtaking the local one…