In message , Mait001
writes

Are we, passengers (sorry, customers) so stupid as to be unable to distinguish
between the Underground and overground?!

ON (the Overground Network) doesn't refer to the whole of the train
system that is above ground.

It is a specific network of high-frequency, metro-style services with an
off-peak frequency of at least four trains an hour. Currently it is
being piloted on four South-London routes (including our local Richmond
line).

To some extent yes, it is a marketing exercise, but the ON also includes
better passenger information, station security and upgraded station
facilities - all welcome improvements.

--
Paul Terry