With the idea of “line lit” signals in mind…I’ve been trying to figure out the new system installed by NS between Johnson City, NY and at least Owego with the changeover to single track. East from end of double track/siding at Hicories park there are two six aspect signal on masts for respective track. About a mile and a half east there is a signal mast with a three aspect color light eastbound and a six aspect colorlight aspect automatic signals westbound.;another mile and a half and there is a three aspect signal in both directions. At the first automatic signal eastbound it is usually clear (green) and the wesbound would show a yellow on the top signal and red on the bottom (meaning the next signal is an interlocing signal and is red). When the interlocking signal in advance is cleared, this westbound signal will alter to reflect green over red (when route through interlocking is clear with a green over red; I have not viewed other aspects as yet). The other westbound signal (further east) will show a flashing yellow when the signal in advance shows yellow over red as described above).
My question is: is there always clear, approach, or restircted signal indications in opposing directions until the dispatcher sets a route for a movement at which time signals opposing the move all are red?
Also I note that these signals are green atop, yellow middle, and red at the bottom. This is contrary to most systems (and the highway system) of red on top, yellow in the middle and green on the bottom. Comments please.
Henry: For reasons unknown to me, roadway traffic signals, which were developed several decades after railways began building wayside signaling and interlocking systems, arrange the lights backward.
Absolute signals are generally designed to be at stop when in the “at rest” condition. When the dispatcher requests a direction of movement, the absolute signals will check to see if it is safe to grant that direction of movement, and if so, will change to proceed in the requested direction, and remain at stop in the opposing direction. After the train passes the absolute signal, it will drop to stop and remain there until the dispatcher again requests a proceed indication. Absolute signals are granting authority, so you definitely do not want a signal system to default to a condition where it is granting authority if you don’t actually need it to grant authority. You want the system to default to stop.
The intermediate signals in effect “look” to the absolute signals to see what to do. If, for example, a westward intermediate signals looks at an adjacent absolute signal, and that signal is at proceed, and there is nothing between the two signals, the intermediate signal will also improve to proceed. So, if the dispatcher has not lined up anything, the intermediate signals will look in each direction to the nearest absolute, which is at red, and choose the appropriate aspect depending upon how many blocks from the absolute signal they might be. If you lit up everything, and supposing you had nothing lined up, the first intermediate approaching the absolute would be yellow, the next flashing yellow, and the next green, assuming a four-aspect system.
And this would be true in both directions simultaneously?
I’m not sure I follow your explanation of highway vs rail signals. On the DL&W and elsewhere as I remember, red was always on top, yellow in the middle and green on the bottom just like highway traffic signals. More involved (signals above singnals and interlocking) signals on the Erie and NYC also were red down to green but you could have a red over green over red, etc. depending on the situation.
But, RWM, I really appreciate your taking the time to explain.
Your systems are different than ours. If everything is lined up for us, we’d get all greens… (with maybe an approach medium/limited, then a limited/medium clear if lined to cross over)
For us, a flashing yellow is an advance approach. Proceed prepared to stop at the second signal…
Many absolute signals are approach lit. The cost savings is too much to ignore. Same holds true for changing locomotive and crossing gate lamps from incandescent to LED. As UP replaced signal systems on the Spine, most became approach lit. Even CNW converted the interlocking at Albert Lea, before the UP merger.
There is no reason to have a signal lit if there is no trains in the area. And there is no reason in GCOR that require it to be lit all the time. if you arrive, and it is dark, you follow rules.
I think I must not have been very clear – I was discussing what the status of the signals would be if nothing was lined and no trains were on the main track. Also, I am only describing only the aspects of a basic 4-aspect signaling system (single head), not the names of the signals or the indications. Railroads differ considerably on signal names and indications, whereas aspect logic is very similar among railroads.
I’m not aware of any significant cost savings for an approach-lit signal. The energy requirement for the signal lamps is a rounding error compared to the energy requirement for the instrument house HVAC system, battery charger, track circuit leakage, and vital circuits.
The reason that crossing signal system lamps changed from incandescent to LED was driven by safety first, and cost only if one considers the potential avoided cost of a grade-crossing collision. The LED lamps are quite a bit more expensive than an incandescent lamp. The electric current draw of the LED lamp vs. the incandescent lamp is again a rounding error.