Does anyone know what the following marking means, when it is used and the date it was introduced? It is a red/white square in Chequerboard format, like the picture below (which may be the wrong way around). I have seen them many times on the walls of bridges.

 




Bob(K)

It is a limited clearance warning board.  It is used to warn trackside staff that there is insufficient space to stand clear of the line when a train passes, so bridges and tunnels are the usual locations, but any trackside structure can have one of them on if the clearance in restricted.


I will find a diagram showing the clearances so that you can see where you should position these signs.

Found it quicker than I expected!

The distance that is referred to as a place of safety varies according to the maximum permitted line speed, as shown below




If any structure falls within these distances then you need one of the previously mentioned signs.

For info, the standard track spacing is shown below

Thanks Chris. As always very full and informative advice. I don't suppose you know what date the signs were introduced? Would they be used in the steam era?

Bob(K)

Once again I've learned something.
Thank you gents!

Sorry Bob, I have no idea when they were introduced.  Certainly they have been around my whole life but that certainly does not cover the steam era!

The Blue and White sign only came in after the introduction of High Speed Trains in the late 1970s and is generally only found on routes where the linespeed is in excess of 100mph, but there will of course always be exceptions.

The circular sign with the person crossed out is much more recent, possible late 1990s onwards?  Previously there would simply be a worded sign, rectangular with a red border, which said "No safe access while trains are running".

If you are running colour light signals and have bi-directional operation you should also have a worded sign, rectangular with a red border, which says "Trains run in either direction on this line"

Chris,

Thanks again. I will leaf through my pictures and see if I can find when they were introduced. Interesting subject though and I certainly had not heard of the blue signs before. Just shows, always something to learn with this hobby.

Bob(K)

this is the frustrating area of the hobby,info,pics what have you in abundence
for loco`s, stock,stations etc, but lineside structure virtually nothing, signs and notices too.
if it wasn`t for Chris and his mine of information, thanks mate.

roll::lol::lol::cool:

Well a quick rummage through some of my reference books shows the signs widely in use in 1962. I can't find any earlier at the moment, but I suspect that all BR period eras can be safely included. Interestingly they seem to be most commonly used on goods sheds and engine sheds, where the entrances are particularly tight. There is little evidence of them being used on bridges/tunnels so far but will continue to look. It will also be interesting to see if they occurred before nationalisation.

Bob(K)