wrote in message
...

It is OK. It is a pity we cannot have two or three fleets covering a
subset of Overground services. These trains could then carry simpler
maps covering the are served.

Are the actual sub-classes split rigidly between the bits of the network
anyway? For example are there now some dual voltage units in regular use
on
the East London?

Not at all split rigidly.

As you probably know, there was originally a discrete number of DC only
units ordered, and this fleet was sized for the original ELL, ie before the
Highbury extension. All the subsequent orders (as the extensions were
approved) were for dual voltage stock, and they can and do go anywhere on
the overall electrified network.

Hence all the dual voltage units need the full map.

Paul S