So, does that make the Forth Bridge a tunnel?
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(Trivia) When does a bridge become a tunnel?
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So, does that make the Forth Bridge a tunnel?
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Methinks, someone needs to rethink the logic of the sectional appendix, excepting the above, and decide what is the distinction between a simple add-on bridge structure and a tunnel of any sort.
alex17595
Member
Is a bridge not just a manmade structure that carries a single road/path/whatever where a tunnel goes under ground level with plants/soil above it and nothing to do with length.
In railway terms a tunnel is a tunnel when listed in the sectional appendix as a tunnel, there are different rules for tunnels than there are for bridges, all tunnels have a number as do all bridges. It has nothing to do with length, type of boring, what it is under it is all down to what it quotes in the SA. For example Gerrards Cross tunnel is under tescos and could maybe looked on as a long bridge but the SA says it's a tunnel!!!!
Peter Mugridge
Veteran Member
Wouldn't it be so much simpler to revert to the older convention that a bridge is built and a tunnel is bored?
When it comes to the application of the rules and regs, quite possibly in an emergency situation, it's far simpler and quicker to determine whether a structure is listed in the sectional appendix or not than it would be to start thinking about how long the structure is and how it was constructed - in some of the more obscure cases, I doubt ten drivers looking at the structure would be able to come up with a consistent answer by the latter methodology, let alone a signalman who can't see it. Either way, it's surely the effects of the structure on the operational railway (length, clearances, positions of safety and so on) that are the important factors to be considered, rather than the method of construction - and, after all, what's wrong with the way things are?!
cirithungol
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When you're traveling from Sweden to Denmark 
So the Metropolitan Line runs in a bridge under Euston Road?
You can as a driver only go by rules and regulations and if the SA says it's a tunnel it is and if it does not it isn't however for non railway this would be completely different. No one including myself have said that the SA is correct however the original question is on a railway forum so therefore the answer to the question in railway terns is correct.
Best answerWhen you're traveling from Sweden to Denmark
PaxVobiscum
Established Member
Joseph_Locke
Established Member
50 yards, for differentiating between how to inspect them.
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Peter Mugridge
Veteran Member
An excellent example, which I make to be around 110m 'long' - and not shown in the sectional appendix as a tunnel.
Interesting, and that certainly makes sense. Would the structure in the above link be treated as a tunnel for inspection purposes then? It's definitely still not a tunnel as far as the operation of the railway is concerned.
Again, the link above (and numerous other examples) should quickly rule that one out!
Dragons live in
http://www.railwaycodes.org.uk/tunnels/tunnels0.shtm Found a 10y !
curly42
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Was told when I started on the railway (1970) that if you could stand a standard length coach under it,and nothing poked out either end,it was a tunnel. If anything showed either end,it was a bridge.
Might not be true but it sounds good enough for me.
Might not be true but it sounds good enough for me.
CarltonA
Member
I think we can divide between what is for railway purposes defined as a tunnel and what is a tunnel as a philosophical question. The latter has been bored under undisturbed material and the former is whatever has been formally defined as such by the railway.
According to the RSSB in GC/RT5180 a Tunnel is defined as:-
Tunnel
A structure provided to allow the railway to pass under higher land, buildings
and/or water, which has been excavated without removing the surface of the
land. The term includes any associated shafts, adits and portals.
It also includes other types of construction, where in the opinion of the Structures
Manager, the structure needs to be managed as a tunnel.
--- old post above --- --- new post below ---
But then again, GC/RC 5603 states:-
Tunnel 1. A STRUCTURE provided to allow a RAILWAY to pass under higher land, buildings
and/or water, which has been excavated either without disturbing the surface of the land
or by the cut and cover method
2. An OVERBRIDGE which is in excess of 50m in length measured along the RAILWAY
Tunnel
A structure provided to allow the railway to pass under higher land, buildings
and/or water, which has been excavated without removing the surface of the
land. The term includes any associated shafts, adits and portals.
It also includes other types of construction, where in the opinion of the Structures
Manager, the structure needs to be managed as a tunnel.
--- old post above --- --- new post below ---
But then again, GC/RC 5603 states:-
Tunnel 1. A STRUCTURE provided to allow a RAILWAY to pass under higher land, buildings
and/or water, which has been excavated either without disturbing the surface of the land
or by the cut and cover method
2. An OVERBRIDGE which is in excess of 50m in length measured along the RAILWAY
Plenty of tunnels under 50m listed in the sectional appendix.
Tunnels affect the way emergency detonator protection is laid (and, to a much lesser degree, assistance protection) - overbridges don't.
How would anyone carrying out emergency protection know whether it is a tunnel or an overbridge? By their route knowledge, of which full information regarding all tunnels would have been gleaned from the sectional appendix where the length, mileage and any local instructions regarding every tunnel on the network is published.
Next point of conjecture - what is the difference between an underbridge and a viaduct...
Tunnels affect the way emergency detonator protection is laid (and, to a much lesser degree, assistance protection) - overbridges don't.
How would anyone carrying out emergency protection know whether it is a tunnel or an overbridge? By their route knowledge, of which full information regarding all tunnels would have been gleaned from the sectional appendix where the length, mileage and any local instructions regarding every tunnel on the network is published.
Next point of conjecture - what is the difference between an underbridge and a viaduct...
Peter Mugridge
Veteran Member
Using the definition above, those will presumably be ones that have been created without removing the surface. Or are there some listed as under 50m long which have been built by cut and cover methods?
That would be the Bridge over the River Kwai.
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