PaulG wrote:According to British Rail GEOGIS Users Guide for 1992:
"A bridge is a structure of any dimensions that enables a railway or road or watercourse to pass over or under another railway or road or watercourse. Normally, its length will be less than 50m. If greater than 50m it will usually be entered as a tunnel.
A bridge span of less than 2m will be defined as a culvert
A bridge span of less than 0.9m will be a pipe.
A bridge of 5 spans or more will be defined as a viaduct."
Regards
Paul
Well that's quite interesting Paul : Thank you.
Noting the the '50' that you've quoted is metres, I wonder this has grown from the convenience of rounding figures, because the conversations with C.Eng'g types which left me with the (verbal) info. about the bridge/tunnel distinction boundary of '50' was long enough ago that it must have been 50 yards (45.72 metres).
Note that that description is taken from a Guide.
(I have inputted data many times onto that system over the years.)
GEOGIS only tells you what is in place on the ground.
The earlier definition of a Bridge or Tunnel will still be down to the name it is given in the Sectional Appendix and as such will actually be down to what the inputter on the day wants to call it, whatever the structure might actually be.
