On 16 Dec, 23:31, 1506 wrote:
On Dec 16, 2:27*pm, (John S.Robinson) wrote:

On Dec 14, 10:11=A0am, (Neil Williams)
wrote:

Not sure, but I noticed new track on the Met at Euston Square last
week, and was astonished to note that it was of the jointed, bullhead
variety.
When are LUL going to enter the 21st century and move to CWR like the
mainline did years ago?

There are two separate and distinct questions he

1. Fishplated v. welded rail: as others have remarked the Underground
has been using welded rails for many, many years. However, the Civil
Engineers always used to complain that the long rails they laid were
then cut into shorter lengths again by the Signal Engineers for
blockjoints. Because of the intense service traditional L.T.
signalling has many more signals per mile, and hence many more track
circuits, than most Network Rail lines.

2. Bullhead v. flat-bottomed rail: Flat-bottomed rail is now being
installed, even in tube tunnels, but this is comparatively recent.
Previously, the B.R. form of flat-bottomed rail installation gave a
greater sleeper-to-railhead distance than bullhead by an amount that
was significant in the close confines of a tube tunnel. There were
also questions about the having to redesign switch and crossing work
for flat-bottomed rail. I'm not sufficiently in touch to know the
details of how these problems were solved.

Thank you. *That is very informative.

Ditto, thanks. There's almost always good explanation for things being
done the way they are (or were), at least in the field of engineering,