Sim wrote:

5. I think the intention is to create a kind of S-Bahn, to take the
German model. The Underground, of course, is the U-Bahn.

I believe the fundamental difference between a U-Bahn and an S-Bahn is that
people who are unhappy with the U-Bahn should try to kick the mayor out of
the Rathaus, whereas people who are unhappy with the S-Bahn should try to
get rid of the Chancellor over in Bonn. This distinction doesn't really seem
to be the case with the Overground.