"Paul Corfield" wrote in message
...

AIUI the ELL is having its power supply, current rails and signalling
all changed to match National Rail standards.

On the face of it, there seems to be little reason why a power supply
upgrade can't allow for the 4th rail to remain while LU stock remains in use
on third rail power, like Putney-Wimbledon, Gunnersbury-Richmond. Isn't the
spec for the third rail position same as NR tracks, and isn't the track new
anyway, or is it only in the Thames tunnel?

The physical integration issue with other lines is different - the
northern section will be linked in on a section that is closed anyway so
no impact there. At the southern end I understand that a flyover is to
be constructed and I imagine there will not be a huge issue with linking
that in - a longish weekend possession could deal with that.

As you say, on the southern end it seems the major infrastructure works are
only on the New Cross Gate branch - so is a temporary Whitechapel - New
Cross only service really out of the question?

The bigger issues concern testing all of the signalling and control
systems and the new rolling stock and training the drivers on the larger
network.

I don't think the signalling in itself could take anything like 2 and a half
years though. The signalling complexity must compare with the current NR
resignalling scheme in the Portsmouth area, in terms of numbers of stations,
junctions, distances, and interfaces with other signalling areas. This is
requiring major closures for about 6 weeks if all goes to plan, although
preparatory work has obviously been done over normal overnight and some
weekend possessions.

Given the ability of the expanded ELL to spread delays all
over north and south London I imagine a lot of time and effort (probably
6 months if not longer) is going to be spent to try to ensure the new
line is reliable from day one. If not then TfL will be paying out a lot
of cash to FCC and Southern for delays to services between Central
London and Croydon.

Agree with this - one of the pitfalls of the line becoming so integrated
with the NR 'networks', given that ELL connects effectively seperate areas
of the NR system, to the north and south.

Paul S