Questions about the Diverging Routes

[Towerman]

Hi!

 

I am a railway dispatcher in Germany / Bavaria and visited recently NYC and its most interesting subway system. My main interests are metro and railway signalling and operation - so I try to extend my knowledge on that topic, also related to the NYC subway.

 

Firstly I hope to find an explanation about the appearance of the Route Diverging Sign. This sign, showing the letter "D" with a number, indicates the speed which applies for movements routed over switches in diverging position. These boards are installed only, if permitted speed for diverging movements is higher than 10 mph. In my (very old!) rule book and in the NYC Subway track book this sign should be white with a black inscription, but I just watched yellow signs showing with a D.

 

It there a difference between white and yellow D-boards?

 

Another subject I would like to know is the pre-signalling of home signals permitting a movement over a divering route.

 

I learned that such signals may be announced by a time controlled "D-Signal". Is it possible, that home signals showing "Proceed on divering route" are not pre-signalled at all (the signal in rear shows green), if the sighting conditions are sufficient for a reduction of speed?

 

Thank you very much for your reply.

 

Towerman

[INDman]

There is no difference between a white "D" and a yellow "D" though I think only yellow signs are used now.

 

As for giving a diverging route at an interlocking, it can only be done if there is a way to ensure that the train has slowed to the correct speed for the switch. I'd have to look for the specific rule. Now if timer signals precede the diverging route, it can be done.

[Eric B]

I wonder if the white D could have been a very old yellow that faded. Or maybe it was just before they came out with or solidified the color code.

When I came out in school car, one of the biggest anomalies was the old yellow R, on the northbound over Snediker. R's are green, since it's telling you "proceed" rather than "caution", which yellow is. This was removed when that stretch of track was demolished in the Atlantic reconfiguration.

[Towerman]

There is no difference between a white "D" and a yellow "D" though I think only yellow signs are used now.

 

As for giving a diverging route at an interlocking, it can only be done if there is a way to ensure that the train has slowed to the correct speed for the switch. I'd have to look for the specific rule. Now if timer signals precede the diverging route, it can be done.

 

 

Thank you very much for your helpful replies!

 

During watching my subway photos I remembered an arrangement of a speed sign with a T-sign. E. g. at De Kalb station on tracks A 3 and B 1. The T-sign denotes the begin of a time control.

 

Is there a difference if a Grade-Time-Control is indicated by a GT-sign or by a T-sign together with a speed sign?

[Eric B]

T with a speed sign is GT. By itself, it's usually ST.

[TheSubwayStation]

Question: are there any timers that are only in effect when a switch is set for a diverging route? I thought I heard something about this, and it seems like it would make a lot of sense to have them. These timers would protect the switch, but wouldn't unnecessarily slow down the trains if the switch isn't set for a diverging route. There are plenty of areas (e.g. n/b passing 23 st, or s/b into 36 st) where something like this would help to speed up the trains and still prevent accidents.

 

Thanks

[Eric B]

Yes, there are some, and it is a relatively newer idea. Queens Plaza is one place I can think of.

[TheSubwayStation]

Yes, there are some, and it is a relatively newer idea. Queens Plaza is one place I can think of.

 

Thanks for answering my question. Isn't there one on the passing 36 St? Any other places where this exists? It would be nice if the would put in more of these instead of the unconditional timers. I don't mind the timers that protect curves, but the ones that are there to protect rarely-used switches get kind of annoying.