whenever I am railfanning I see signals, but I haven’t a clue what they mean…
what does red, yellow and green mean?
Any Ideas???
Thanks[:D]
The colors on the signals you see are referred to as signal aspects or apperance. What the signals mean is called the indication. So when a dispatchers tells a crew signal indication, it means proceed according the inication of the signal. The different color arrangments designate speeds and diverging routes, etc. Each railroad has its own set of signal arrangements. From the dispatching office all we can do is request a signal to line up for the intended route. If the route is lined and clear of opposing movements I get a green line across my screen for that selected move; I have no idea what the crews see. It could be very restrictive or Clear, it just depends on several factors.
Dear Chris,
You are asking information on a subject which can be a lifetime pursuit of information.
In a condensed version:
Signaled lines are divided into “blocks.” Each block is governed by a signal at each end.
A green signal (called proceed) means the immediate block and the two blocks after it are clear. A yellow signal (called approach) means that the immediate block is clear but one of the two blocks after it is occupied. Red (stop) means that the immediate block is occupied. The reason two blocks will display yellow is that, if only one block did, it is conceivable that two trains heading towards each other would pass signals at the same time, and each would find itself going at full speed and come across a red. The yellow provides a “cushion;” speed after a yellow is usually 30 mph.
At a switch, the top signal is usually for the main route, the lower for the diverging route. Three head signals are rare out West, but when they are found, the middle signal is usually for the “middle” speed route.
For example, red-over-green means proceed on the diverging route, red over yellow means approach on the diverging route. Red-over-red means stop. Sometimes you will find flashing yellow or yellow-over-yellow (often away from a switch), which means the next signal is for a diverging route.
Flashing red and lunar mean the same thing–proceed at restricted speed. Generally, anything with flashing red means restricted speed, called restricting.
The Altamont Press Timetables list signal aspects and their meanings.
Sincerely,
Daniel Parks
To be clear, I was talking about Automatic Block Signals, while Nathan was talking about Centralized Traffic Control, in which the dispatcher controls train movements by changing “control” signals.
Good point trainjunky. I was about to mention that myself. There are a series of Control Points on the railroad I dispatch and inbetween are automated blocks.
On a somewhat related note, I have a question concerning the Trains webcam at Rochelle- would it be possible to add signal displays near the four corners of the webcam picture that show what the respective signals are indicating for a given frame? Would be kinda neat to have an idea where the next train is coming from. I suppose that that would violate some homeland security rule, or be too expensive to somehow sense the control lines…
green you go…
yellow you slow
red you stop
and if your not sure about the rest…you go 10mph
csx engineer
There is a second set of interpretations of the multiple head signals. In Canada and on some US roads, the signals are speed indicators. some indications only require one light, while other, more complicated ones take three. e.g. rule 417 “medium to limited” is red over green over flashing green and means “Proceed, medium speed passing signal and through turnouts, approaching next signal at medium speed”. This is a combination of a medium speed through the switches and a medium speed to the next signal. This is probably going straight through the switch while the curved route would get a “limited to medium” indication.
I see two headed signals at junctions, while the three heads come up nearer to terminals and yards. Note that these signals don’t actually give a route indication.
I thought that with yellow you are supposed to speed up to get past the signal before it turns red.
Jay
Are you able to set a control point to cycle for a certain number of trains or to automatic block mode? I realize not all systems are the same, but on Q racetrack where i watch, an absolute control point signal for some crossovers seems to have different operating modes. During rush hours and on weekends, the top signal will cycle green, red, yellow, flashing yellow, green for a series of trains coming through on the same routing. At other times during weekdays, it will display a green only when a train is about to come through. As the train passes it will go red and stay that way, often for quite a while. Later, it will go directly from red to green when the next train is imminent, I assume because the dispatcher set it. When the train passes it will go back red and stay that way.
The signals at an interlocking can also indicate route. While there are some standard aspects, there might be some unique to a specific location.
As trainjunky said, you could make a lifetime pursuit of the topic. Here’s just one site on the subject http://n6ecv.net/rrsignals.html that I found on Google. I haven’t looked through it, but saw several familiar links.
csxengineer summed it up rather nicely, though. You just have to know which stops and go’s apply to you…
A good book on the subject. “Railroad Signaling” by Brian Solomon. It is a good way to get a basic understanding of what you are looking at when you see a signal.
Here is more reading on signal aspects and rules.
The signals mean that if you don’t understand them and the rules that go with them, you do NOT belong there unless you’re with a railroad employee who DOES.[}:)][}:)][}:)]
(and railroaders can pass red signals dependent on the rulebook and signal territory which came as a shock to a highway patrolman here in CO a few years ago; the signal had a numberplate in CTC/ GCOR territory in this case)
That’s only if you’re driving a car, not a train![:D]
The variety of signal indications is really amazing – one of the things I’ve always wondered (being a lowly ground pounder type engineer, not a throttle in the hand engineer) is how one remembers them… I like CSX’s synopsis!
Sounds like there is a story behind that statement MC.[8D]
CTC systems often have a “fleet” mode which clears the same route and signals in the same direction for as long as you want and some have a 'stack" mode that allows you to program a series of different moves into the the system and then it executes each route in sequence.
Dave H.
I know what the old Pennsylvania position light signals mean:
Three lights vertical: Same as a green signal
Three lights diagonal: Same as a yellow
Three lights horizontal: Same as red.
The LIRR still uses these.
Now what do the different blades on semaphores mean?
IIRC, exactly the same thing as any other form of signal. I’m sure one of the references provided already will cover semaphores, too. The type/shape of blade does have significance in certain situations, such as home, advance, and train order. There are also upper and lower quadrant semaphores.
According to my handbook that signal means call the ib dispatcher and complain and inform him that you are on the q116 and why is he running you through the siding? Then you call all your buddies and tell them what a goof the dispatcher is. If thats not good enough you right stuff about him on the bathroom wall everywhere.