The signal prior to a red, will it always be yellow? Or is it possible to have a green and then have the very next signal be a red?
“Always” is a dangerous word on the railroad. But generally, yes, any red signal should have an approach leading up to it. There are exceptions, covered by various timetables and the like, hence my first sentence.
Couldn’t a clear slgnal go red at any time for a variety of reasons that might take effect after a train has passed the previous clear signal?
First: red…next yellow…next could be yellow over green or green if automatic territory next would probably be green. Special rules, interlocking, or other circumstances could be different.
Second, Bucyrus…any signal could go red at any time, but once a route is set and the signal cleared it should stay cleared when a train is in the block and approaching the signa. Any shunting of the next block will set the signal at red or, if an interlocking signal, it can be taken away but with a penalty: a timer will lock the interlocking for a specified time in hopes that all traffic will stop and cool heads recompose. In automatic territory a clear signal can be passed with the next signal green but another block a head a signal can be changed to red so the approaching signal will drop to yellow, not red. Again, distant signals, home approach signals and home signals are all defined in timetables and rule books according to railroad beyond NORAC rules.
Maybe a rail break? Thinking that would be a corner case, at least maybe in winter?
Sure, but for normal operations with nothing going wrong, you should not have a stop without an approach. But yeah, if a condition happens that fouls the circuit, then you could have a stop (or restricting/stop-and-proceed/restricted proceed) pop up without prior warning. There are rules to address that.
PS. Amazing how some simp feels the need to rate these posts with one star…
[:-^] That is right Mr. Train~~~ still water does run deep.
Cannonball
Never assume anything. Years ago on my territory we had a crew running on clear signals. Came around a curve and just beyond the next clear signal was the bottom of a train. They hit the standing train, and by miracle no one was killed. Some bad injuries though. A signal malfunction was blamed.
Not a matter of assumption - but the fact that we run on signal indication. Only alternative is to always run at restricted speed…
If you can’t trust the signal indications, then us engineers become nervous wrecks, signals can always fail of course, but that is more of a hiccup in the journey than dangerous, known as an infastucture SPAD where I come from.
Actually try having the auto-pilot land a commercial airliner in ZERO visibility conditions - had to do that once when I was an airline pilot. You want to talk about trusting the instrumentation and having a freaky feeling? Literally we felt the “thump” of the wheels and the brakes automatically engage before we even saw anything outside our cockpit…
On the CN where I am the signals go from Clear (solid green), Advance Approach (flashing yellow), Approach (solid yellow), Restricting (flashing red) to Stop (solid red)
Last month in a heavy rain there was one southbound train following roughly a block behind the one ahead of it. The hogger of #2 had things timed out pretty well as the CTC signals would go from “Advance Approach”/flashing yellow to “Clear”/green about 15 seconds ahead of the lead loco. After he approached a CP the next signal was approach lit (wouldn’t light unless a train was between two points) and still dark. The second he crossed the CP and the intermediate light came on it was red. I heard the dynamics and airbrakes getting kicked on. He did manage to stop short of the signal and they had the RTC dialed up before they stopped moving. The fact that there was a speed restriction and the train wasn’t at full track speed probably helped keep the stopping distance short enough.
Great question! and all great answers. Alot of accidents occur on the approach(yellow) signal. The Approach rule is simple: Proceed prepared to stop at the next signal.
The ‘dark’ signal - which should have been illuminated - by itself should have been a warning that something wasn’t right. That may be why they were already slowing down, per the rule that is along these lines: “If a signal is imperfectly displayed, then treat that signal as displaying the most restrictive indication that it could.”
- Paul North.
Recently we have had a new Control Point installed on my territory. The new Control Point exists only on one track in multiple track CTC territory and is only 1100 feet from a previously existing Control Point.
We had occasion recently where a train had the signal lined at the previously existing Control Point, but the New Control point was at STOP account of a Code Line failure. The train had a Approach at the previously existing Control Point, which authorizes 30 MPH prepared to stop at the next signal…1100 feet is not braking distance for any freight train at 30 MPH - fortunately the train involved was leaving a Yard Track and was not doing 30 MPH and was able to get stopped…but the designers of the New Control Point have designed in a accident waiting to happen…it will be interesting to see how the company responds.
I understand there are two general philosophies in designing signal systems. One is “route signals”, where the signals display the route. It is then the responsibility of the train crew to control the train speed appropriately. The example above seems to indicate a weakness of this method.
The second is “speed signals” where the signal indication specifies the allowable speed, generally slow (15), medium (30) or unrestricted. (A fourth is a restricting signal, which is prepared to stop in half the range of vision.) The rules specify the speed at the signal itself, and the speed at the signal ahead. This can be a more complex system, particularly where the block distances are less than braking distances and require three heads on a signal mast to cover all the possibilities.
John
I believe the New Control Point was installed by the Chinese Menu method…Pick 1 from column A and this was done without considering the real consequences of the situation. At the present time, the New Control Point is nothing more than a power switch feeding a industrial spur normally serviced by the once a day local freight…it may become a more significant facility in the future. Situation probably would not have come to light without the incidence of Code Line failure, as the normal practice is to line signals through the New Control Point to the following Control Point.
I suspect that the company will change the indication at the Previously Existing Control Point to indicate a ‘Slow Approach’ when the signal at the New Control Point is not lined. This would convey Slow speed over the Previously Existing Control Point prepared to STOP at the next signal…to date no changes have been made.
[quote user=“cx500”]
BaltACD:
Recently we have had a new Control Point installed on my territory. The new Control Point exists only on one track in multiple track CTC territory and is only 1100 feet from a previously existing Control Point.
We had occasion recently where a train had the signal lined at the previously existing Control Point, but the New Control point was at STOP account of a Code Line failure. The train had a Approach at the previously existing Control Point, which authorizes 30 MPH prepared to stop at the next signal…1100 feet is not braking distance for any freight train at 30 MPH - fortunately the train involved was leaving a Yard Track and was not doing 30 MPH and was able to get stopped…bu
Re-reading Dan’s post, I don’t think that there was anything wrong about the signal being dark. It being approach-lit, it wouldn’t light up until the train entered (occupied) the block beyond the CP that was ahead of the intermediate in question. I think maybe the way Dan worded it, it gives the impression that the signal should’ve been illuminated before it was.
We have some longer blocks where the next signal doesn’t light up until you’re about half way thru the current block. I’ve always thought it would be nice if approach-lit systems turned on the next two blocks.
Dan, what kind of signal was the intermediate? An old searchlight perhaps? The reason I ask is that we had one
Jeff is right-it was my wording of the sentence. The light in question is a tri-light & bi-directional at MP 183.2 on the Neenah Sub. It does not light until a train passes SOUTH DIXIE (south of the signal) or CP SOUTH NEENAH (north of the signal). I’ve made it a practice to check the signals when trackside to confirm what I’ve heard or presumed about the train’s path down t
Signals are separated by blocks. Blocks are separated by insulated rail joiners. Within each block a small amount of electricity travels on the rails. Any time something shorts the block, such as a railroad wheel then that block shows up as occupied. Control Point (CP) Signals are controlled by the dispatcher. They are normally located at the entrance and exits of sidings or crossovers while in double track. Intermediate signals (with either offset signal heads and/or displaying a milepost number) are Automatic Block Signals (ABS) and are not controlled by the dispatcher. ABS signals are often located between two CP Signals. Typically, at least one block must be unoccupied to display a clear signal, however when blocks are short an Advanced Approach, Approach Restricted or Diverging Approach Restricted will sometimes proceed an Approach Signal.
Whenever you have a clear signal followed by a stop signal something has triggered a block light to come on in the next block after the train passed the clear signal. This could be a lowboy tractor trailer hung up on a crossing or some type of event mistakenly caused by a railroad employee. Although these things can happen they are rare. In the event this occurs, my job as an engineer is to safely bring the train to a stop even if it means passing the stop signal. At that point we would immediately contact the dispatcher and the conductor may have to run ahead of the train and provide flag protection if necessary.
One red signal you are allowed to pass is a Restricting Signal ABS signal. Trains passing a restricting signal must proceed at restricted speed, looking out for obstructions and able to stop within half the range of vision.
Hope this helps!
Tim