Paul Scott wrote on 28 October 2009
10:14:47 ...
D7666 wrote:

I would have thought the most significant length constraint would be
Willesden Junction (for LO trains obviously not SN). To extend that to
8-car would involve bridging WCML and that would not come cheap. As
there would be no benefit to LO in 8car trains if Willesden Junycion
were never done, the entire cost of 8car works on WLL would be born by
the SN operation.

I expect WJ (HL) won't be anything like as difficult to extend to 8 car
length once the current 4 car extension is completed. Getting across the LL
tracks, which is underway now, is the main problem to solve.

On the current track alignment, an extension to 8 cars would have a very
narrow platform at the eastern end. You'd have to move the tracks
further apart, and there could be problems with adjacent lines and the
curvature at that point.

Having said that - I'm not too sure where the new reversing siding is going
with respect to the new platform ends - that could prove a limiting factor in the
eastward direction as well...

The siding will almost certainly go in the space between the NLL tracks
between the Harrow Road bridge and Kensal Green junction. There's
certainly room for a 6-car siding there, possibly longer. In fact there
used to be a siding there, the remains of which are still visible.
--
Richard J.
(to email me, swap 'uk' and 'yon' in address)