12-28-2011, 03:21 PM
torikoos Wrote:Which of the signal heads would be for the right hand track , the top or the bottom?
Sorry I missed this part. All signal heads, or lights, on a single mast (pole) govern the same track. Each track has it's own signal head or heads on it's own mast. In the examples above, even though the left signal has 2 sets of lights, top and bottom, this is ONE signal ASPECT that INDICATES what a train is allowed to do. If the top has a green light, and the bottom a red light, the ASPECT is CLEAR, the INDICATION is PROCEED.
If the top was yellow and the bottom red, the ASPECT is APPROACH, the INDICATION is PROCEED PREPARED TO STOP SHORT OF NEXT SIGNAL.
If the top was red and the bottom green, the ASPECT would be MEDIUM CLEAR, the INDICATION would be PROCEED, NOT EXCEEDING MEDIUM SPEED THOUGH INTERLOCKINGS AND SWITCHES AND THEN PROCEED AT MAXIMUM PERMITTED SPEED.
The ASPECT is what the signal shows you, the INDICATION is what the aspect tells you how the train is to proceed (or not proceed as the case may be)
Typically, on the eastern railroads I worked on, intermediate (or permissive) signals were located between interlockings where there are no switches or diverging routes (not including industries) and had only 1 head. Signals 1 block away from an interlocking had 2 heads, and interlocking or absolute signals had 3 heads. An example of a 3 head signal would be red over yellow over green. The ASPECT is MEDIUM APPROACH SLOW, the INDICATION is PROCEED NOT EXCEEDING MEDIUM SPEED THROUGH SWITCHES AND INTERLOCKINGS AND THEN PROCEED APPROACHING NEXT SIGNAL NOT EXCEEDING SLOW SPEED.
It gets pretty complicated after awhile. I know I was long winded, sorry about that. These are, of course, railroad specific and are the rules I knew 10 years ago. They may be different on western railroads.
-Dave