On Tue, 26 Apr 2011 11:22:27 +0100
Roland Perry wrote:
I don't know. What I do know is that modern road bridges and viaducts to me
seem to be very over engineered given the total weight they'd ever be expected
to carry. Eg , that M1 viaduct that had a fire underneath.

That's built to carry three lanes of 40 ton HGVs.

Even 3 HGVs only weigh the same as a single locomotive. A rail bridge may have
to carry 2 locomotives plus their trains at the same time.

Rail bridges OTOH seem to be somewhat slender in comparison.

The busway bridge is pretty slender too. Here's someone's picture of it
under construction.

http://mw2.google.com/mw-panoramio/p...m/12999233.jpg

It would be interesting to see how slender it looks with a few hundred tons
of concrete busway on top of it.

coupled with the fact that it would have provided a useful diversion
route for the ECML.

Single track and non-electrified (ignoring the reverse at Huntingdon for
a moment) does not make a very useful diversion.

If the line had been re-opened electrifying it would have been the only
sensible option unless DMUs were to be run all the way from london or have a
DMU shuttle service from cambridge.

B2003