I train-watch at CSX’s busy double track main line just into Florida… I usually go near a spot with two crossovers and a turnout to a busy subdivision all protected by four 3-over-3 light signals, obviously under CTC and dispatcher control. Curiously, a mile down the #1 track has a simple 3-light signal which is always green. I’m pretty sure it’s still CTC territory. Is this just a simple ABS/APB signal? Can track #1 be ABS/APB under TWC while track #2 is CTC in certain spots? Does the dispatcher have control over all signals in CTC? How can I tell which signals are speed controlling and which are route controlling for RRs that use both types? I’m kinda new to this stuff…
Volumes have been written about signals, literally. Check Kalmbach or your local hobby store.
There was recently a thread about the signalling for a single passing siding. It went to three pages. You can read it here.
There are some links in the thread to other signal resources.
Can’t answer questions about CTC, etc. I don’t have a clue, either. There are those who may have specific knowledge of the area who can address your questions, though.
It’s beyond the interlocking with the crossovers, right? If so, then it is simply the automatic block signal for the next block beyond the one that starts at the exit for the interlocking. For the most part, as long as there’s not a train in the next two blocks, it’ll be green.
The dispatcher only controls the route at interlockings. Once he sets the route, he put up the signal. The local interlocking logic decides what signal to display depending on the route and the occupancy of the track ahead. Some RRs don’t indicate any speed with their signal aspects for diverging moves, relying on the timetable to tell the engineer what speed to operate if diverging. The signal indication will simply be “diverging clear”, for example. Other railroads include some speed info with the aspect, displaying “slow clear”, “medium clear” or “limited clear” depending on the turnout geometry in the route.
I’m sure that if you were specific about the lines you were looking at (where they lead to from your spot in Jacksonville), someone might be able to tell you, from a timetable or his own knowledge, which rules (Traffic Control System or Automatic Block) govern the lines or control points in question.
I had to smile at the “always green” signal. If the signal were always green for a given direction, there would be no need for said signal. I’m sure you mean that you’ve never seen it with any other aspect. If it’s on a single-track line covered by TCS (CTC on nearly every railroad except CSX), TCS would clear all of the signals in a given direction between one control point and the next (in this case, probably from the plant with the crossovers to the next controlled siding). Depending on how it’s set up, signals in the opposite direction could be either green or red (it’s been explained to me before, but I still can’t understand clear signals in both directions!).
I’m pretty sure there’s a website out there that would give you the aspects and indications you could expect to find on the control point signals governing the crossovers. My advice would be to keep watching those signals, and see how they’re lit for trains taking various routes. This will take a bit of observation, I’m sure, but you’ll soon be able to predict the route a given train will take, just by looking at the signals. Basically, that’s what railroaders do, too, or should be able to do, according to the rules.
On the signal with one head, there may be a permanent sign attached to it (you will find no such sign on the signals governing the crossovers). That will tell you a lot about the signal. If the sign displays a number, the signal is probably an intermediate signal, as Don said. If t also has a letter underneath it, it may indicate a little more about the signal itself, or conditions beyond it. For example, CSX has a letter “D” on its distant signals. If there’s a signal for the direction going toward your cross
Which control point are you refering to?
Not so amazing, actually. As I understand it, a single track, signalled in both directions but with no trains present (and not being approach lit), should show all green in both directions. Depending on how far out the signals “reach,” the signals will show and “approach” aspect, then “stop”.
An engineer who fails to reduce speed accordingly for an approach will may well overrun the next signal, which will be even ore restrictive - even stop.
Of course, the train approaching from the other direction will get the same indications.
Stalemate occurs when both are facing a stop, and each other.
This assumes that there is no other mechanism for controlling entry into said stretch of track, or that it was ignored. In reality it should never occur, since the DS would likely either hold one train until the other cleared, or would arrange a meet at a controlled (or even uncontrolled) siding.
I probably have parts of this wrong (or the whole thing…), but here’s a single track, signalled in both directions, with two trains approaching head on:
In this example, the upper head indicates the occupancy of the next block, and the lower head indicates the occupancy of the block beyond.
If there were no trains, all of those head would show green.
I usually watch in Callahan, 25 miles or so (?) from Folkston, about 1/4 mi. north of where the Baldwin sub splits off and heads SW. It’s a little closer than Folkston. I have CSX’s signal speed aspects there down pretty well… I wouldn’t know why you’d use a different system (it’s not like the engineer has a choice of which route to take), but like I said, I’m not too experienced. I didn’t even know CSX doesn’t use CTC! Anyway, it seems that in CTC territory, the dispatcher has control over remote turnouts and signal speed/route indications for those plants, and if no turnouts or other signal-controlled instructions occur in a block, a protective ABS signal can suffice… does that sound right? Then pure ABS or APB can be used where TWC or DTC is used instead of CTC… this makes sense to me, but I don’t know if it’s right. Oh, and to respond to tree68, I think that on a single track with bi-directional traffic, that stretch should have a absolute permissive block system at a minimum. Once a train enters that block, all opposing signals are turned red to prevent exactly what you are illustrating.
CTC v TCS = semantics
Different carriers refer to the same operations by different term.
CTC = Centralized Traffic Control
TCS = Traffic Control System
Part of the issue you are facing is that every railroad had and continues to have different standards as to what intermediate (aka: number-plated, ABS, Stop and Proceed) signals do in CTC/TCS territory.
On the former Northern Pacific the signals in CTC were usually lit full time. Typically they defaulted to (1) green if the block was clear and next signal was at least yellow or (2) to yellow if the next signal was red. If the dispatcher had set up the contolled signal (aka: Absolute, Stop and Stay, Home, Positive) at a control point (aka: interlocking, plant, power switch) to authorize a train coming from the opposite direction, say Westward, then Eastward intermediates would drop to red. Once that train went byand cleared the block, they would return to the default color, assuming the dispatcher did not immediately authorize a second Westward train. Thus, in the middle of a single track section, two blocks away from the control point, you could see green signals in both directions, assuming no trains in the vicinity and no trains authorized by the dispatcher.
On the former Chicago Burlington and Quincy Lincoln to Denver line the signals were also lit continuously; however, when a Westward train went past an Eastward intermediate signal, the Eastward intermediate signal stayed red. It would not go green (or yellow) until the dispatcher authorized an Eastward train from one contol point to the next. Thus when you went down the highway you would typically see green (or yellow) intermediate signals in one direction and red in the other, again, assuming no train was close by.
On the former Great Northern the intermediate signals were normally kept dark. When the dispatcher authorized an Westward train from one control point to the next, all the Westward intermediates would light up to green, or yellow. The Eastwar
Back in 1954, when I was getting into learning more about railroading (I saw my first copy of Trains in April of 1952), I had the impression that all single track signals were green in both directions, except to indicate an occupied block. That summer, my mother had to take the SAL from Camden, S. C., to Petersburg, Va., and I went down to Camden to see her off. While waiting for the Palmland, I went out and looked at the sb signal just south of the station, expecting it to indicate when the nb train was approaching. The sb signal was not lit, and I realized that the SAL did not follow what I had assumed was the standard practice, and I then had the thought that SAL signals were lit only for trains approaching them. As with nomenclature, each road had its own thoughts on signal operation. I am not sure, but I believe that the SAL main did have CTC (or TC, or TCS)
In 1951, I enjoyed a day trip from Birmingham to New Orleans on #43, standing at the rear and watching the semaphores clear for nb traffic, and dropping to Stop for following sb traffic.
Johnny
New CSX Signal installations, from my observations, are constant lit signals. The area around Callahan has had new signals installed…at least new within the last 15 years. One must remember when looking at CSX signalling that CSX has been formed from the following fallen flag properties - B&O, C&O, ACL, SAL, RFP, LN, CR (both NYC & PRR segments), CEI, MON, PLE as well as other smaller carriers such as Georgia RR and A&WP. In their day each of these carriers had their own signal systems with their own signal standards, not only that, as signal technology progressed and the head of each carriers Signal Department changed - so did the standards for each carriers signal system. All carrier wide signal systems are implemented piece meal, over a period of years or even decades as both need and capital abilities to finance the projects rise to the top of each carriers need list. In actual operation each signal installation has it’s own unique set of operating parameters.
There are multiple strategies used by Train Dispatchers when it comes to lining signals for routes, especially in the age of Computer Aided Dispatching. Some line trains signal to signal with manual dispatcher control. Some utilize the automatic lining abilities of the CADS system. Others, map out their strategy for the trains they have on their territory, setting up meets and passes and manually lining the signals using a ‘stack’ feature of the CADS system to line and reline signals for the next proper route each time the signal is used by a train. In some cases signals can be lined for a train that is 100 miles from the location of the signal. Without knowing the detailed condition of the Train Dispatchers territ
Go to www.alcrughomepage.com. He has some interesting info on signaling.
Justin
Justin, the link doesn’t/didn’t work for me. I suspect it may be due to a typo…maybe a K in exchange for the C? A google search produces Al Krug’s Home Page.
-Crandell
CSX installed new TCS on the A&WP sub from Palmetto south starting 2 years ago. The CPs are constantly lit both directions. All intermediate signals are only lit when either side of the intermediate is occupied with both directions lit Opposing red and traveling is whatever is allowed from farther down track.