Railroad signaling is one of my favorite aspects of railroading, but I’m having trouble understanding how cab signals operate. For those who don’t know (but want to follow along), these are indications in the locomotive cab that augment or replace fixed wayside signals.
My question relates to typical US pulse-code signals, developed by the PRR and now the de facto standard in the country. Several of my local railroad lines use NORAC Rule 562, with wayside signals at interlockings only – all intermediate automatics are cab-only.
I understand that this style of cab signal is continuous and signals can upgrade or downgrade at any time…but how do signal blocks work between interlockings? Are there specific blocks that are controlled by cab signals, exactly like a standard signal installation, but without the physical waysides? How are they marked?
I consider myself very signal-savvy, I’m just having trouble wrapping my head around this one. Any insight would be appreciated! Thanks!
In the pre-CSX days on the RF&P, we had non-wayside blocks between interlockings if we ran the lefthand main. (3 track north or 2 south). The exception being the intermediate immediately preceding each interlocking. Block limits were designated by number plates on the backside of the intermediates faced for normal, righthand operation. So, yes, there were specific blocks, as in wayside. I’m pretty sure other carriers systems were set up the same way.
There are many different ways of doing this, and I do not know all of the details.
LIRR used the PRR system, Metro North uses a different system, I do not know what AMTK or NJT uses, but when running on MNCR tracks, AMTK needs to use the Metro North system, when running in New Jersey it likely uses the old PRR system, unless that has been replaced. LION does not know. LIONS worry about wildebeests, let others worry about interlocking.
But like ewe, LION likes signals and interlockings. This is what him built for his own railroad…
Actually the locomotive cab signal displays the condition of the block you are in. There is never a display of the next signal ahead. As you mentioned, Conrail practice (and maybe PRR?) was to install a “cut section” which would drop the cab signal to restricting part way through the block, approaching a stop indication. CSX has adopted this practice on the RF&P sub at some, but not all home signals. All signal modifications seem to be randomly applied, which is very frustrating when operating over the territory!
Don, your explanation was perfect. Thanks for taking the time to write that all out – that was exactly what I needed for my understanding to click into place.
Two more questions:
To add to that, how does it work when a train is switching within a block?
On lines without fixed wayside signals (NORAC 562 or equivalent), how are the block divisions marked?
That is the best way to put it. Cab signals display the condition of the block you are in, wayside signals display the condition of the block you are about to enter.
Before the UP added wayside signals to the former CNW’s ATC, there was no formal marking of block boundaries at most of those locations. There were insulated joints and a relay house. As you became familiar with the territory, you started to know where they were and an idea of where a preceding train was when you got train control. The ATC is a two aspect, clear or restricting form of cab signal.
Now that UP has added wayside signals to the ATC territory, you can get a restricting cab signal at a wayside displaying an advance approach.
Wow! Two aspect, clear and restricting? Must be a nightmare for train handling! We have four aspects, clear with freight overspeed set at 60.4mph on the newer power, approach-medium/limited set at 45mph, approach set at 25mph and restricting, which also will allow 25 though the rule limits you to a maximum of 15 (and you had better be prepared to stop within one-half your range of vision). Is there an overspeed setting on the former C&NW territory, or do you simply acknowledge the downgrade and use your best judgment?
The overspeed setting (freight service) for ATC is 73 mph. When you get a restricting cab signal over 40 mph, the high speed setting, you have 6 seconds to get below 40 (not an option unless you’re right on the bubble) or go to suppression to avoid the penalty brake application. Get a restricting cab below 40, you have 70 seconds to get below 23 mph, the slow speed setting. Between 22 and 17 mph there is a continuous audible warning, so on a restricting cab top speed (conditions permitting, remember it is Restricted speed and that rule applies) is 17 mph. About every 90 seconds when on a restricting cab, the ATC needs to be acknowledged, like an alerter.
The UP also has 4 aspect coded cab signals on the original UP side, but there is no overspeed setting for the indications. You only need to acknowledge the aspect change, there’s nothing that forces you (other than following the rules) to actually slow down to the corresponding indication.
The details are beyond me on this one. Might involve magic. I might need another night in a Holiday Inn Express.
But, there is some sort of circuitry that knows what the direction of travel is set for when the route is set and the signal is put up at the upstream interlocking. It tumbles down through the blocks, setting all the opposing signals to stop and toggles the block signals to work in that direction.
I know that once you have passed a control point and entered a track segment with the traffic set opposite your direction of travel (signal problems, talked by the red,etc.) your not going to get a more favorable (than restricting) aspect until reaching the next control point (interlocking, generally) . Tis indeed dark magic!
For the record, Jeff, it’s 100 seconds between buzzers when you’re in Restricting, starting any time you release the brake (I had nothing better to do once, and timed it…it was consistent). Of course, that was 40 years ago.
Jeff, of course, we know that Carl was relegated to the yard for who knows how long; have there been such changes since he was allowed out on the road?[:)]
As to the number of aspects for cab signals, the Southern rule book of about 1940 showed, as I recall, three: clear, approach, and stop. Does anyone know if the Southern ever used cab signals, and , if so, where? Sad to say, I did not find my copy of that rule book when I moved this past March; I hope it did not absolutely disappear during the thirty-eight and a half years that I lived in one place. I did find some treasures that had put themselves into places that were difficult to find.
I considered myself fortunate to have obtained that rule book. Not long after I started to college, the agent who had been in my home town for several years and was patient with me was moved to Forest City, N.C., which was on my hitch-hiking way to and from college. Once when I stopped to see him, he had just received the new rule book, and I asked him if I could have the old one; he was not certain if he had to turn it in, and told me to wait a while. The next time I stopped to see him, he gave the book to me.
ATC pretty much works the same as when Carl went out on the road. Only real difference is in the equipment and how it works. Just like everything else, more electronics and computerization of components.
Are you saying that the Southern used cab signals in conjunction with ATS? I know that the Southern had ATS on many of its lines: Bristol-Memphis, Chattanooga-New Orleans, Cincinnati-Chattanooga, Salisbury-Morristown, Biltmore-Hayne, (Alexandria?)Monroe-Birmingham, Haleyville-Jasper, Ala., some others–and all of these had ABS. I was unaware that the ATS also used cab signals; indeed, the two times that I rode a Southern passenger engine (in 1969) I did not notice cab signals. Would not the presence of cab signals also have been mentioned in the ETT, as the presence of ABS and ATS was?
Thank Goodness for electronics in connection with these cab-signal installations! I well remember that when new units would arrive on the railroad, they had to remove the cab-signal equipment from older power to equip the new ones (I was really shocked to see some SD40-2s that no longer had cab signals because of the SD50s and SD60s). Once UP came on the scene, a whole lot more units had the potential to come over our main line, so you needed units that can read both types.
I always thought it would be smart for CNW to convert the line to UP’s cab signals and retire its archaic system. I guess that’s all moot now, with ATCS coming down the road–they can get rid of everything else.
