I have a scenario that I can’t figure out.
You are on a double track mainline and approach a 3 way cross-over. The left one heads to the south track from the north track of the main, the straight obviously keeps you on the same track and the right leads you into a yard.
If this is CTC territory and has a signal, how would the engineer know the difference if he was crossing-over to the other main versus into the yard?
It all depemds on the previous signal.
For instance, if the train was to go into the yard it might receive an approach aspect on the previous signal and a restricting aspect on the signal at the switch.
If the train was to cross over to the other main, it might receive an approach diverging aspect on the preceding signal and a diverging clear or diverging approach aspect on the signal at the switch.
Once again, my favorite train-watching spot–Elmhurst, Illinois–provides the answer. Eastbound commuter trains always cross over at Park (Track 1 to Track 1, in a place where the main line narrows from three tracks to two); they get a Diverging Clear (red-over-green-over-red) if the track is clear. Trains headed into the yard off either Track 1 or Track 2 will receive a diverging approach (red-over-red-over-yellow) for the low-speed route.
Yah, like the other two said, you normally get a restricting signal when entering a yard. In Canada if the train was entering the yard it would get a Clear to Slow, (yellow-over-yellow) at the approach signal before the interlocking then a resticting, (red-over-red-over-yellow) into the yard, or get a Clear to stop, (yellow-over-red) at the approach and the restricting into the yard. If it was staying on the main but just switching tracks it would have a more favourable signal. Such as Limited to Clear, (red-over-flashing green-over red), or Medium to Clear, (red-over-green-over-red), something like that,
Carl, not to nit-pic, and perhaps I’m going by the “old” book of rules, but the aspect for a diverging approach used to be red-over-yellow-over-red; the signal you describe sounds like restricting signal. An ‘approach diverging’ signal with show the aspect of yellow-over-yellow-over-red.
It also depends on whose operating rules are being used. I have an old Southern Railway and an old Penn Central Rules for Conducting Transportation and the same aspect may have two different indications, depending on which rule book is being used.
“a diverging approach (red-over-red-over-yellow) for the low-speed route.”
That’s a restricting signal in anybodys book!!!
Jim (both of you), if you check it out, Diverging Approach (Rule 9.2.11, as shown in the CORA book) can be either red-over-yellow-over-red (as it would be along the main line if the track weren’t clear) or red-over-red-over-yellow. A restricting signal at Park (used to be HM) still involves a lunar white light in the lowest position (No possibilities for the Restricting signal on UP–Rule 9.2.13–show any yellow in them at all; they’re all lunar white and red). A lot of changes in both plant and signal indications were made at Park a couple of years ago, and what used to be logical to me was replaced by this new “logic”.
As for the signal by the gravel pit (used to be the distant signal for HM; I forgot what Mark told me to call it now), it will show either yellow-over-yellow-over red for the mainline diverging route, or yellow-over-red-over-yellow for the routes into the yard. Both are possible aspects for Approach Diverging, as shown in Rule 9.2.5.