WSXFan said:
The work to do it would not balance out any benefit coming from the extension.
I disagree. From an operational point of view I think it would be beneficial, definitely from LU's point of view as they would be able to run the entire Central Line with just two service patterns (in theory). It would also give the Greenford branch a much higher service frequency, and better station facilities (if LU took them over).
The easiest way of doing this would be to provide LU with a separate set of tracks to the West of Ealing Broadway, but there isn't enough space for this and space probably can't be created due to the presence of people's gardens (not to mention Ealing's council offices, and a large multi-storey car park which spans the current GWML formation).
Obviously signalling would be a problem. I imagine it would be near impossible to run Central Line ATP alongside NR signalling. Perhaps the trains could be driven in manual along the stretch in question? That would solve a few problems.
The layout at Greenford would also need modification, as the current infrastructure is not designed to facilitate through running from the branch on to LUL metals.
All in all it's a good idea but would be a nightmare to implement. Although if they got it right, IMHO, the benefits to passengers would be huge.