Mixed Signals

Trains Magazine General Discussion
1

I have a signal related question this morning.

Below I have drawn a theoretical track arrangement with numbered boxes where I would think signals would go for this track arrangement.

My questions are:

  1. I think that signals 1 & 2 would face RR East. 3, 4, & 5 would face RR West. Is that correct?

  2. Would the signal at 3 be one lens, either red or green (is that an ‘absolute’?) and ‘always’ red unless access to mainline is granted?

  3. Where would the crossover from the “1 & 5” main to the “2 & 6” main have it’s signal?

  4. Would the crossover signals (for both mains & directions) be two triple-headed signals (G/Y/R)? If so, would the top ‘head’ of the signal control the non-diverging track and the bottom head the diverging track?

  5. Have I missed anything?

Thanks in advance to anyone kind enough to reply.

2

There would be no signal at 4.

1, 2, face east.

3, 5, 6 face west.

All signals are absolute.

2, 5, 6 likely to have two heads.

1 likely to have three heads.

3 could be a dwarf signal or a three head high.

Nick

3

I’ll try this one for you, Dan; I have most of the morning… First of all, this is only a theoretical exercise, because railroad rules vary, and some of the railroads in the real world would have noting to do with, for example, lunar white lights. Your main lines also have to be signaled beyond this interlocking–in other words, this network of signals will not exist in isolation from the rest of the railroad. There will be distant signals a block away in either direction on the main lines.

First of all, Signal 4 is unnecessary.

Signals 1, 2, 5, and 6 will each have three heads, the top two of which will be capable of displaying red, yellow, and green, and the bottom one red and probably lunar white. Everything would face away from the switches, to “protect” them.

Signal 3 would be a two-headed signal. The top head will always be red, the bottom will be capable of displaying green, yellow, red, or lunar white.

All of these signals would be absolute signals, so no number plates should be in evidence.

Your question 1: Correct, except that 4 won’t exist; 3, 5, and 6 will face RR West.

Your question 2: Both heads of Signal 3 would be red most of the time. When your train is lined up to leave the siding, you could get a green (track clear beyond the signal), yellow (next signal will be red), or lunar (block ahead has train, engine, or broken rail).

Your questions 3 and 4: Signal 1 would govern everything for trains coming from that direction. On Signal 1, a yellow or green on the top head would indicate a routing through to 5; a yellow or green on the middle head would be a lineup to 6 (in both cases, dependent on conditions in the block beyond the next signal down the line), and a lunar on the lower head would indicate a route from 1 to 3, assuming your siding is not protected by the signal system.

Your question 4: For Signals 1, 2, 5, and 6, the middle head will govern the crossovers, telling the train to proceed through the crossover at th

4

GCOR rules, CTC.

Signal 4 wouldn’t be there.

Signals 1-2-5-6 would have two heads. All 4 signals would face away from the crossovers. All 4 signals would display diverging signals.

Signal 3 would be a single head dwarf or high mast signal and would face away from the switch.

All signals would display stop (absolute signals).

5

So it should look like below?

On the 3 headed signal (#1) top signal controls the ‘main’…would the 2nd one control the siding or the crossover?

6

It looks like a sort of compromise between Dave’s ideas and mine (mine has more lights, hence more possibilities). But now you have the signals in the right places and facing properly.

7

Might I suggest taking what has been put forth so far and comparing it to this, which is the CNW signal aspects from the CORA book (at least that’s what the website says).

8

I think I like not having the lunar aspect…and for the area I have in mind…the crews could just as easily call the dispatcher to ask for the light they need…I think lol.

9

Very interesting perusing, and thanks!

10

That looks a lot like the west end of Framingham Yard on the old Boston & Albany, except they’ve got another siding on the other side of the main.

11

Most GCOR roads have changed “Restricting” to a flashing red instead of lunar.

Signal #1 to answer your question. If the speed thru the crossover turnouts or into siding were the same (siding would further have to be signaled) you could use the middle head for both. If the siding turnout speed is slower, then the bottom head would be used. If siding is unsignaled then the bottom head would be a “Restricting” indication of your choice.

12

We still have a few lunars but I keep hearing how they are going away.But your set up looks right to me.

13

(bold emphasis mine)
That was my thought: slower speed into the siding than the crossover. Thanks for that!

I know some have stated that the default display for these lights would be ‘stop’. Would there be any situation or reason the default display would be ‘clear’ or any other indication?

14

OK–using flashing red would probably reduce the number of heads on the mainline signals from three to two. If you want, we can go over the possibilities signal by signal sometime.

IMHO, you’d also be best served by two heads at Signal 3. A Restricting signal would get you out of the siding, but then (absent cab signals) you’d be stuck at restricted speed until the next signal. A Diverging Clear would allow you to speed up as soon as you cleared the switch if your train was short–or, if a long train caused “Delayed in block” to come into play, it would allow you to speed up when you saw a clear route up to the next clear signal.

One thing about a Restricting indication–it usually is not an automatic thing. It has to be intentionally granted by the control operator (dispatcher, tower operator, whatever).

I mention this in connection with your question about default indications. It’s almost always stop–that’s fail-safe. However, I recall a time when the clerks struck the CNW (and every other railroad as well), back in the early 1970s. I happened to be driving in Des Plaines that day, and saw that the home signal for Deval Tower was set at Restricting (lunar white) for the westbound main track (something I’d never seen on that signal before). The operator may have been instructed to do that to allow CNW’s commuter trains to keep running.

15

Your ways work but with a twist things can change, in a traffic controll area this would be all absolutes but if it was hand throw switches then things change signal 1 and 3 are absolutes signal 4 would move east to protect trains on the main from trains out of siding and would be directly across from dwarf signal in siding. Signals 2-5-6 all would be 2 headed signals with number plates. the key is that the 2nd way is in a abs and tc controlled area, there is many ways to protect moves with out stopping trains and diverting trains also.

16

Ok, I’ve drawn the whole ‘block’. I have included what I would have guessed as the signals in the area. RR East of the block there is a diamond (2 blocks away) and RR West of the block is double track for a while (many blocks).

17

If the tracks are bidirectional, seems to me there should be a signal between 4 and 7 facing ‘east’.

Art

18

Art’s right about that.

I also have a problem with “advance approach” being a default indication for anything here. These are all absolute signals at control points, hence the default is “Stop”. I’d need more information about the surrounding signals (blocks away) to know why “Advance Approach” is needed at all.

If you have an entire block between the end points of the siding, you’d probably also want block signals on the other track, even if there are no switches involving that track.

19

Yeah, Art’s right. You need an east facing signal between 4 and 7. The default indication of any controlled signal is STOP.

Advance Approach is used where the blocks are short, and you need more warning time before encountering a STOP. It should be noted that not all roads use Advance Approach, instead preferring to use two Approaches.

Carl’s got a point too. Depending on the distance between 4 and 7, there may be one or more Automatic Block signals between them. In this instance, the siding is probably not signaled other then the entrance and exit signals.

Nick

20

None of the heads “control” a particular track, other than they all “control” whatever track is beyond the signal.

The combinations of signals form an aspect and the different aspects have indications, which are the instructions for what that combination tells you to do.

So if the siding is bonded and the signal displays red over yellow you could be either going through the crossover or going into the siding. The non-red signal not being at the top indicates a diverging signal, not which track. If it was tied to which track then at every crossover on a 4 track main you would need 4 heads.