On Thu, 18 Aug 2005 15:27:52 +0100, Tom Anderson
wrote:

(i assume because digging wide deep tunnels was ruinously expensive).

I suspect so. A modern equivalent, the Merseyrail Loop, is very
nearly[1] full mainline loading gauge because modern tunneling
equipment made it rather easier.

[1] PEP-derived EMUs, e.g. 508s, fit, but not the slightly larger
Mk3-derived units like 455s, as I recall. The structure gauge
difference can be seen quite nicely in those 455s that have a spare
508 car inserted. Not enough to have a major impact on passenger
comfort or internal layout, but enough to be visible.

Neil

--
Neil Williams in Milton Keynes, UK
When replying please use neil at the above domain
'wensleydale' is a spam trap and is not read.