On Apr 10, 8:53*am, D7666 wrote:
On Apr 10, 8:44*am, John B wrote:

if there are reasons 26 metre cars can't be used;

I would suggest there would be door access issues with stock longer
than 20 m.

On 20 m cars like 317/319/321 and 450/377/375 and 376 et al door
spacing is approx 1/3 and 2/3 car. A 26 m car would be more like 1/4
and 3/4 door spacing - which would lead to longer dwell times - any
more to place doors further towards the middle of a 26 m car would
have to larger a throwover at curved platforms - of which there are
too many stations to resolve.

If you take a look a 444s at Waterloo where the country end of a 10car
is on the curve its easy to see how much a 23 m car throws over. *444s
have end-ish doors so its no big deal - but imagine even 1/3 + 2/3
spacing on one of those cars leads to a big gap.


The end doors only solve the problem when the doors are on the outside
of the curve (if you see what I mean). If the platform is on the
inside of the curve, then the end doors are further away from the
platform than at the 1/3, 2/3 positions. You can see this more clearly
on some of the tightly curved platforms on the underground. At some
platforms the middle doors have the smallest gap and at other
platforms the end doors are 'best'. Best example I can think of, off
the top of my head, is Bank Central line.

I'd have thought going the other way - to *shorter* but articlulated
cars might be better.


I certain agree with this.