dpeltier As recently as 12 years ago, the Norfolk Southern line through Urbana, IL had an old semaphore signal serving as a fixed distant signal for the diamond crossing with the CN mainline. Turns out semaphores can last an awfully long time if the moving parts don't ever have to move. It's probably still there today. Dan
As recently as 12 years ago, the Norfolk Southern line through Urbana, IL had an old semaphore signal serving as a fixed distant signal for the diamond crossing with the CN mainline. Turns out semaphores can last an awfully long time if the moving parts don't ever have to move. It's probably still there today.
Dan
I think there still are a few semaphores around Des Moines, also on NS lines, used as distant signals. There used to be the distinctive CNW upper quadrant semaphores used as distant signals at Webster City IA. Now I'll to make a trip up there to see if they are still there.
The nice thing about semaphores is if the light is out, if the position of the day indication (blade) can be seen it governs.
The NS signals don't have lights, the CNW/UP were lit up. Both sets permanently fixed at Distant Signal Approach.
Jeff
dpeltierNot exactly
For the record - my reference has more to do with general signalling (ABS), not special applications. This is rather like traffic lights - if the traffic light is dark, your supposed to treat it as a stop sign (although some people seem to think it's permission to blow through the intersection...).
Particularly with searchlight and tri-light signals (G, "Darth Vader), one lamp out can turn a clear to a stop, as evidenced by the story about the lightning strike.
But it's all good information that shows how signals work.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
tree68 jeffhergert Not exactly. Fair enough - thanks for the qualification. The main point is that a bulb out will foul up the works.
jeffhergert Not exactly.
Fair enough - thanks for the qualification.
The main point is that a bulb out will foul up the works.
Not exactly
This is strictly a technicality and definitely going off on a tangent, but it is possible to have a signal whose most restrictive aspect is identical to its mst favorable aspect, i.e. a signal that can only ever display one single aspect.
The FRA requires a distant signal in advance of every interlocking on every mainline route (with some exceptions). For a route that doesn't have block signals, the distant signal will usually display Approach if the signals at the interlocking are not lined up for that route, or something more favorable than that for trains that are already lined through.
If the timetable speed as you approach the interlocking is 20 MPH or less, however, FRA allows you to just display a "fixed" distant signal... i.e., a signal that always just displays an Approach indication regardless of what's happening at the interlocking. If a signal like that loses or a bulb burns out, it makes absolutely no difference in how trains operate at that signal.
ccltrains Finally we arrived in Austin four hours late. My wife met me at the station. I was all excited and wanted to tell her about the trip. Her comment was: Shut up and get in the car.
Sounds like you lucked out! My wife would have told me to get a cab or bus home.
Several years ago I had the privledge to ride in the cab of the Amtrak train between Dallas and Austin. Shortly after leaving Fort Worth we had a big electrical storm. The lightning knocked out all the signals for the rest of my trip. When we came to a dark signal we had to take the most restrictive action and stop. The engineer would call Omaha and get permission to proceed. A few miles further was another dark signal and the same procedure was repeated. Finally we arrived in Austin four hours late. My wife met me at the station. I was all excited and wanted to tell her about the trip. Her comment was: Shut up and get in the car.
... Insulated joints that no longer are (either by the endposts being crushed or the insulated "barrels" around the bolts getting worn down and causing a shunt....aka the signal maintainer got lonely and wanted some company at 2am
On the B&O CPL's a single colored bulb failure would not 'screw up the works' As the colored aspects each had two bulbs, the absence of marker lights reduced the speed to the lowest speed permitted by the colored lights.
Never too old to have a happy childhood!
jeffhergertNot exactly.
tree68 An important consideration is that a dark signal is considered to be a stop signal.
An important consideration is that a dark signal is considered to be a stop signal.
Not exactly. A signal that is imperfectly displayed, or absent (dark) where one should be displayed, is to be considered as displaying it's most restrictive indication. If it's a controlled signal, then that would be stop. If it's most restrictive indication is restricting or restricted proceed, then the train wouldn't need to stop because of the rules. Just proceed at restricted speed through the block. That still slows things down, but at least with those you don't need to wait 30 minutes for the dispatcher to answer the radio each time you encounter a bad intermediate signal.
We don't have them anymore, but a stop and proceed would only require a train to stop before proceeding at restricted speed. For those non absolute signals, no dispatcher action required.
In my experience the most common cause of 'signal failure' was God and throwing lightning bolts of hundreds of thousands if not millions of volts at 21st Century signal equipment designed to operate on millivolts - lightning protection is only so good and God can defeat it despite man's best efforts.
Now a days most (but not all) switches at remote controlled interlockings (and manned interlocking for that matter) are electrically operated 'dual control' switches. When there is a lack of electrical power, the switches can be operated by crews by using the 'hand' feature that is built into the switch machines when the crews are authorized by the Train Dispatcher (or Control Operator) to line the switches for their movement. Some pneumatic interlockings still exist - switches in these plants CAN NOT be operated by crews and trains will be delayed until the Signal Maintainer arrives and restores the plant to operation - either with the Train Dispatcher lining routes or with the Signal Maintainer lining routes at the direction of the Train Dispatcher.
tree68A failure involving a switch might make it difficult to impossible to make the necessary moves.
Any number of things could cause that to happen - loss of power, bulb or LED's out, relay or circuit board failure. The list goes on.
It's my understanding that the DS can talk trains past failed signals, but at that point s/he becomes a traffic cop, having to authorize moves that the signals would otherwise handle automatically.
A failure involving a switch might make it difficult to impossible to make the necessary moves.
Possibly not a failure but the signal indicating "Stop" to the engineer / motor-man. A signal failure could result in a deadly train collision. A common reason ( among others) is to prevent a moving train for colliding with a stalled train, or a train plunging off an open bridge. Signal systems a complex in design and operate with very complex electrical relays, and theWh tracks are seperated into "blocks". I had the good fortune to enjoy a tour on the New York City Transit System's signal training facility. A very critical signal operation because of the brief time-interval between a departing train and a arriving train. With a "green " signal the train enters a "block". Relays "detect" the train entering the block , and immediately the signal indicates "Stop". The "Stop" signal will only change to "green" until after the train has left, or "cleared" the block.Another important redundant safety is the "de-rail" feature which will de=rail the train should the "stop" signal be un-heeded.
Any usual electrical problem like stuck, dirty or otherwise defective relays or contactors, or short circuits can cause a block to appear occupied when it really isn't. So can broken rails, but they are probably less common.
Power switch machines can also break down, or fail to line because a rock or some such object has been blown into the points by a train. In this case the train crew will get written permission from the Dispatcher to pass the stop signal and manually operate the switch, they will then also have to operate at restricted speed to the next signal or "block end" sign.
We also hear the term "code line failure" on a regular basis, this is when the Dispatcher has lost communication with some outside installation(s), perhaps because of one of the above reasons. I imagine computer problems in the Dispatching centre could have a similar effect out in the field.
All the outside failures seem to occur more frequently in cold and/or rainy weather, or during heat waves.
I'm not a signal maintainer, this is how things appear from a train crew's point of view.
Greetings from Alberta
-an Articulate Malcontent
Number 22 was delayed between Austin and Taylor yesterday because of signal failure. On several occasions I have been on trains that have been stopped because of signal failure.
What are the major causes of signal failures and how often do they occur?
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