But why on earth have they lumped all the Overground lines together as
if they were one line. The Underground lines being different colours
and names makes it pretty clear where trains are going. But the
Overground lines as shown make it appear that you could, for example,
catch a train direct from West Croydon to Richmond or Clapham Junction
via Gospel Oak, should you want to. At the very least, the East London
Line Extension should run in to Highbury parallel to the line from
Stratford, and terminate there. In the same way as the Metropolitan
does at Aldgate or the District at Edgware Road.

You could say the same for the DLR.