"Tom Anderson" a écrit dans le message de
h.li...
On Fri, 19 Aug 2005, Alan (in Brussels) wrote:

"Nigel Pendse" a écrit dans le message de
...
"Ian Jelf" wrote in message

In message , Tom
Anderson writes

Conversely, London never had the el-to-subway transition that built a
lot of the NYC system (there are one or two examples of this
happening in London, though).

I'll probably kick myself when you answer this.......but where are
there any examples of this happening in London?

How about where the District and Picc climb out of their subsurface and
deep level tunnels at Earl's Court to just below ground level at
Hammersmith and then up a steep gradient on to the viaduct by
Ravenscourt Park? Or where the Wimbledon Line climbs on to a quite
high viaduct in Fulham? And the Central west of White City?

Yes and no, because although those are indeed examples of what the OP of
the text

Is that me?

meant, what he actually wrote (as he clarified subsequently) referred to
the construction of tunnels *to replace* surface or elevated lines.

That's exactly what i meant - tearing down elevated lines and digging
tunnels along the route.

OK. Let's try again.
a) It was indeed the message by Tom Anderson that included:

The biggest physical difference between the networks is that London's
lines are mostly in deep tunnels - 'tubes' - in the clay layer (or
something) ~20 metres below the surface; only a few lines (the Circle
line, the lines coming off it at tangents, and the East London line) are
built at shallow depth using cut-and-cover. AIUI, New York's lines are all
shallow (except for PATH and such). This means that stations are rather
different in structure, and the tunnels, and thus the trains, are smaller
(i assume because digging wide deep tunnels was ruinously expensive).
Conversely, London never had the el-to-subway transition that built a lot
of the NYC system (there are one or two examples of this happening in
London, though).

that raised this issue. Another poster then asked for specific "examples of
this happening in London", on the assumption that Tom was referring to
"el-to-subway transition" in the sense of "tearing down elevated lines and
digging tunnels along the route", as he wasn't aware of any. Then a third
contributor offered examples of places where a UndergrounD train runs out of
a tunnel and onto a viaduct (or vice versa), and I intervened to try to
clarify the situation by giving examples of where a surface rail line in
London (whether on a viaduct, embankment or not) has been *replaced* by one
in a tunnel (see text extracts above).

b) Careful examination of the last sentence of the last quoted paragraph
above reveals that strictly speaking the last part is incompatible with the
first part (if "London never had..." there can't be "one or two examples of
this happening in London"), hence the confusion.

ISTM that this aspect of the comparison has now been exhausted.

Regards,

- Alan (in Brussels)