Silly question, Maybe - Maybe Not

[Anonymous]

I have always been interested in trains and model railroading. The other day I was parked by the RR tracks near my house and I was looking at the lights along side the tracks and it suddenly dawned on me, I had no idea how to "read" the lights. There are two sets of tracks running through this particular area, they are shared by CSX and SEPTA. I got to wondering how the trains know which light is for them. Theres two sets of three lights in a circle, one over top of the other. Which set of lights is for which set of rails ? Perhaps someone could post a visual aid to help ??
Thanks

[Big_Boy_4005]

A signal like that could mean a number of things depending on the track configuration and the railroad. Generally the top set of lights will tell the engineer about the track condition in the block ahead. The lower set could be the indication for a diverging route, or the block beyond the next block.

The CSX and Septa engineers follow the same rules. The signals are for all trains using that track, and mean the same thing to all engineers on that line.

Say there are no switches ahead, and the aspect is green over yellow. That would mean that there is a train 2 blocks ahead. As long as the two trains continue to progress at similar speeds, the engineer in the following train will continue to see green over yellow at signals he approaches. If the train ahead stops, as the following train closes the distance, the following train's engineer will see yellow over red. Time to slow down and be prepared to stop at the next signal.

This kind of signaling is important on lines with commuter service, because of station stops. If the schedule doesn't keep trains separated, the signals will.

This may or may not be what you are seeing. Try watching during rush hour, and see what the signals do.

[tomikawaTT]

Two signal heads one above another in commuter territory almost certainly indicates short blocks and closely-spaced trains. Since the engineer (or motorman, if running electric MU trains) needs to know how close he is to the train ahead, two signal heads can keep him informed about what to expect for the next five blocks.

Green over green - no train less than six blocks ahead. Proceed at full speed
Green over yellow - train 5 blocks ahead.
Yellow over yellow - train 4 blocks ahead.
Yellow over red - train 3 blocks ahead.
Red over yellow - train 2 blocks ahead.
Red over red - absolute stop - train in the block just beyond the signal.

An employee rule book will give you the permitted speed past each indication, and also its exact name.

The Japan National Railways achieved a very similar result with a single five-lens head.
It could not display red over red, so red alone was absolute stop. Red over yellow was slow walking speed.

[nbrodar]

Dan,
You must live up near Woodbourne and Nashamity.

Generally, trains are governed by the signal to the right of their track. There are exceptions:

Where a signal bridge exists, trains follow the signal directly over thier track.

In double track territory, it is common to place signals to the "field" side of the track.

Also in double track, where both sets of signals are mounted on a single mast: the left set governs the left track, and the right set the right track.

All signals in a vertical line govern the same track.

tomikawaTT signal indicatations are sorta right. But in reality, the signals govern permitted speed, and not actual track conditions. Track conditions, route, and trains ahead are inferred from the speed displayed.

Nick

[Anonymous]

nbrodar Actually I live in Cheltenham. The R-8 runs by my way two blocks away. Also CSX runs trains up the same line then at Cheltenham station they split R-8 Terminates at Fox Chase CSX continues up through the northeast. Whats strange is CSX trains run north on northbound Septa tracks and they also run south on them. They switch somewhere down in the Olney section of Philly I believe. Thanks for all your responses I'm going to try to check them out during the rush hour and see if that helps me.

[nbrodar]

Dan,

It's been awhile since I've run up there, but that's probably Wayne Junction. CSX only has rights on track one, so that's why the trains run north and south on the same track. It's also where CSX crosses over to SEPTA to go up to Lansdale.

Nick