On Sun, 14 May 2006 19:00 +0100 (BST), Colin Rosenstiel wrote:

When the designed the A stock, they built prototypes to try out new
ideas. The coaches before A stock were compartments and the A stock
was a kind of compromise between a normal underground carriage and a
compartment stock coach.

Not exactly. They converted parts of compartment stock vehicles for
trials but they weren't very close to the eventual A stock design I
don't think.

Why "S" for the new stock? The last surface` stock was "D".

I don't think it's supposed to be an alphabetical progression -
there's no B Stock. I've always thought (someone correct me if I'm
wrong) that A is for Amersham, C is for Circle, and D is for District.

The new stock will be common to the whole subsurface network - hence S
Stock.

Returning to the topic of interiors, there are good reasons why Met
trains have 60 seats per carriage while Circle trains have 32 (in
carriages of the same length) - Circle trains are less frequent and
more crowded, and mostly used only for short journeys, while the
average journey length on the Met is a *lot* longer. To me it seems
like madness that the new stock might all be fitted with a common
"compromise" interior that suits neither line well. From my
(admittedly armchair) point of view, it would be much better to
semi-permanently fit the stock for each line with an interior similar
to the current ones (or at least using them as a starting point). This
would require the stock to be long-term allocated to a particular
line, but I don't see why that would be a big problem, with the siting
of depots already suited to this arrangement. Short-term transfers of
stock between lines would still be possible - it would just mean the
odd train running around with an unsuited interior (rather than every
train on the Met/Circle). Long-term transfers would require an
interior refit, however.