Bryn666 wrote: ↑Tue Oct 13, 2020 13:47
But this is still not apples with apples is it - railway engineering is completely different to road engineering in terms of materials and structural content.
Yes and no. In other threads you have been keen to make out there is some sort of absolute separation between the disciplines when the reality is somewhat different.
There is 'railway engineering' as in things like track, traction power and signalling systems and there is 'railway engineering' as in things like bridges, embankments, tunnels, drainage, etc
Basically when it comes to the underlying groundworks, things like embankments, cuttings, draingae need to be built to the same standards regardless of whether you are building a motorway or a railway. The tragic derailment at Stonehaven shows what happens if you try and economise (as the Victorians did) in a time with ever more frequent storms / extreme rainfall events.
Also because it is now a requirement to have decent track side access paths (so as staff are not forced to walk on the tracks for fear of falling down a steep embankment for example), plus wider track spacing to ease the aerodynamic issues at higher speeds etc, your average new build double track railway now needs the same footprint as a S2 road.
Consequently until it comes to lay the track, HS2 is basically being built in the same way as a high quality S2 road and thus no more expensive or technically challenging than any other new build road project would be (assuming that NIMBYS demanded said road be put in lots of long tunnels so it doesn't lower their house price)
Thus the main difference between road and rail construction is simply the volume of work - i.e. because a dual carriageway is wider than a railway more earth needs to be moved, bridges need to be wider, etc.
Now I know it could be said that earthworks / bridgeworks etc are actually civil engineering rather than specifically road or railway engineering disciplines, but its interesting to consider how as the roads are getting more congested, several principles (if not the technology as such) that started out on the railways have migrated over to the road network.
For example a 'Smart' motorway requires hundreds of vehicle sensors (think track circuits on railways) to help the system determine what speeds need to be set. You have MS4s (think signals on the railways) at frequent intervals to set speed limits, Cameras to enforce them (think TPWS on railways). You have a network of emergency phones (think signal post / level crossing phones) linked to a 24/7 control room (think signal box on the railway). Finally you have the Highways agencies looking at developing stalled vehicle technology for its ALR motorway schemes (think obstacle detection at level crossings on the railways).