UK Aspect Signals

can some tell me how far apart uk aspect signals should be on branchline wheather it be 2,3,4 aspect colour light signal

thanks

Hi There. The answer to you question is dependant mostly on line speed. Any train travelling at it's maximum permitted speed for that line must be able to stop before a red signal after receiving a cautionary aspect using a normal brake application (i.e. not needing to resort to emergency or even a full service brake application). So a line where high speeds are permitted will have vastly greater distances between a signal able to show a caution and the next signal capable of showing a danger signal than the kind of line you describe. Gradient and local variables will also be factored in of course so that these distances will vary somewhat. If you run a few tests braking various train types from their max. permitted speeds as you pass your caution signals you'll get a fairly clear idea of what feels comfortable and this will be fairly prototypical.

I drive trains in central Scotland and on the Cobinshaw or the West Coast Mainline we run at 90 or 100mph for miles without seeing a signal ...but then as you approach urban areas or areas with junctions the signalling is much more dense as the line speeds are so much lower. It's really all about being able to stop inside your red signal safely.

Hope that helps.

Define branch line! If it is a single track branch or secondary line then signalling will be provided at and on the approach to crossing loops or junctions. You would not usually find intermediate signals mid-section, unlike other parts of the world. A simple single track branch line might not have any signalling at all beyond its junction point, if one train working is in operation, other than a fixed distant approaching the terminus. Other secondary lines operate under remote arrangements, with points indicators and stop boards with the driver required to obtain a token or staff from a machine and permission to proceed. In some locations RETB (radio tokens) are used and the Cambrian Lines in Wales now use the sophisticated ERTMS signalling system to control train movement.

Cheripok has given good insight into colour light signals. Broadly speaking on (say) a 100 MPH main line under 4 aspect signalling these will be spaced around 1200 yards or 3/4 mile apart. That gives a braking distance of around a mile and a half from sighting the double yellow, to coming to a stand at the red. However in more lightly trafficked areas, colour light signals were simply installed to approximate where old manual signalboxes were taken out (the Devon banks between Tavistock Jn and Totnes is an example of this) and the block sections are several miles long. In this case you would get a colour light distant signal at sufficient braking distance from the next "home" or stop colour light signal.