Tuesday, January 08, 2008

Railroad Signal Lights

From: "Steve Jutras" sjutras2003@yahoo.com

I live near a railway and wondered what the lights mean on the poles; sometimes we see different patterns and wondered what they signified. It's the one with three lights on it. They can be all Red or mixed with Green, Yellow. Could you tell us how to read them?


Anonymous Anonymous said...


This is a subject of a book or two.

Signal aspects, names and indications, although pretty much standard these days, can vary somewhat from road to road. You will find signal aspect are listed in Special Instructions that are included with the timetable or rule book.

I am most familiar with the ATSF signals, so what I say refers to ATSF operations and may differ from UP, NS, CSX, etc. You read a signal from top to bottom.

First you see a signal mast with 1, 2 or 3 lights. If the top light is green, that is a clear signal and means Proceed.

If it is a 2 light signal with a yellow on the top and green on the bottom, that means Approach Limited, proceed prepared to pass the next signal at the specified speed and to advance on the diverging route. (divirging route means that you are going to leave the main and head into another main or on a branch).

If the yellow light is flashing, that means that you will approach the next signal and that will be a solid yellow.

If the signal is yellow/red then you approach at medium speed and advance on a divirging route.

If the signal is yellow/lunar, then you will maintain restricted speed.

If the signal is red/green or red/red/green, then that is divirging clear, proceed on the divirging route. The red at the top means that the main route is not available and the divirging route is clear.

Now a red signal on a mast means stop. If it's an interlocking home signal, then it's an absolute stop. If there is a number plate or a G on a plate (G meaning grade) then it's a permissive stop where you can either stop and proceed at restricted speed or if you are driving a high tonnage train, then just keep going at restricted speed since it's hard to get a tonnage train going again on a grade, but notice that the block ahead may be occupied, so you need to be prepared to stop in 1/2 the distance to the obstruction.

That's basically what it's all about. If you can give me a road and what you actually see, perhaps I can help you a little.

I think that just about every road has a web site and it never hurts to ask them or see if they have posted on their site special instructions or signal aspects. Most roads are, in my experience fairly fan friendly since most of the rails I know are fans themselves.



1/14/2008 3:29 PM  
Blogger CPRR Discussion Group said...

Also see A History of Railroad Signals: The telegraph and the closed-track circuit made railroads safer.

10/22/2013 2:32 AM  

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