I was touring the CP/Soo Line Tomah Sub (formerly the MILW La Crosse Division) and came across some signals that I don't understand. Mostly I saw lots of three light signals which I assume are Red / Yellow / Green much like regular traffic lights - Red is stop - Yellow is a restricted speed and Green is Go. What I didn't understand were the four light signals. These were around the start of passing sidings and I remember some near a junction at Tunnel City. Anyway a photo is worth a thousand words: My question - how does this work? What sort of signals would an engineer see and what would they mean? I found some stuff on the net but they all dealt with one, two and three light signals. BTW - this is the 'normal' three light signal I was seeing all over the Sub If these don't show R-Y-G please clue me in on how they work to
Rob I am not familiar with the SOO but some railroads use a Lunar Aspect which could be the 4th light unit. I will have to do a little checking to see what I can find and get back with you.
Rob - I did some checking but did not find any signal aspects for the Soo but did find in the General Code of Operating Rules that several railroads used a Lunar aspect as a Restricting indication. In such a case the Green would be Clear, Yellow is Approach, Red is Stop, and Lunar is Restricting. I can not quite tell from the photo if it is a power switch or a spring switch but if the siding was unsiganaled, meaning no track circuit to indicate it was occupied, the proper aspect to an unsignaled siding would be Restricting. This would allow the train to proceed at not exceeding restricted speed prepared to stop short of an train or obstruction within one half the sight distance. It the switch is powered it is probably cTc territory and the aspect for a route lined to the siding would be Restricting. If it is a spring switch the train would have to stop and line the switch and then the signal would display a Restricting signal to indicate the route was lined for the siding. If anyone has the Signal Aspects for the SOO let me know if they do show a Restricting aspect.
It is CTC. The two signals in the distance (facing the other way) also have 4 heads. The switch is powered. (I have heaps of pictures of the whole area.) I don't understand what you mean by lunar - is it a particular colour? I did find some stuff about interlocking signals and was thinking that the fourth head was to indicate for the siding, but I thought interlocking signals were always two seperate heads. I have a CP/Soo timetable for this sub, but could not find any info on the signals - I'll look again.
That was my first thought, that it gave an aspect for the routing as well, but then why would the signals for exiting the siding have the extra light as well? They have no routing options? Four aspect signals like that are very common in the UK, but have a totally different context unfortunately, so likely have no bearing on this.
Arn't 'dummy' heads used in interlockings to clearly identify them as non-permissive stops? But then I thought stops in CTC were never permissive unless a sign identified them as - like on a grade. I did find the signal pages in my timetable but it is from 1995 so may not help in this case - I say this because it only shows three head signals - no four head signals. Lunar is shown. The different aspects for RESTRICTING are: One head: Lunar Two head - top to bottom: Lunar - Red Two head - top to bottom: Red - Lunar Two head - top to bottom: Red - Flashing Red Three head - top to bottom: Red - Red - Lunar Three head - top to bottom: Red - Lunar - Red One to Three heads all Red with number plate. Is "Lunar" a white or blue light? I still don't get the term. I don't know how this all relates - what seems most likely to me is that this is an interlocking signal and the top three are for the pimary route and the bottom light is for the diverging route.
A lunar is a yellowish white aspect! If you think this is confusing ,on the monon or wabash or some road back in steam days a lunar was a proceed, a blue was resticting and of course red was stop! I have an old magazine here some where, I'll try and find it an get a clarification
The lunar signal is a blue white color. Go to this site and way at the bottom it shows a dwarf signal with red, lunar and yellew colors. The site is at http://www.emdx.org/rail/signaux/SignalNain/ The signal you took the photo of would only have one color at a time lighted so it would be a one head signal. A two or three head signal has a space of 3 to 5 feet between the heads. This signal is a color light type that can display 4 aspects. The opposing signals which also have 4 aspects would use the lunar/restricting aspect as a return to train signal. As an example if a train stopped and went into the siding to set off cars at an industry whan they returned they could get a restricting aspect to return to their train. The restricting aspect would indicate that the route was properly lined and locked over the power switch. Hope this helps.
Yes Gil you have helped heaps. I think I can make heads and tails of the rules now - the key information is that this is a one head signal that can display 4 aspects. Thanks!
Happy to be able to help with signal questions. I don't have all the answers but do know where to go to find the answers and still have many friends in the business.
On the issue of signal colors, many southern railroads back in the 1920s and 30s used lunar/white for clear indications, green for approach and red for stop.
The style you asked about is usually arranged to show from top to bottom Red, Yellow, Green & Lunar. The other type of color light arranged in an inverted V Yellow O O Green Red . . .O Either type can be modified to the customers specs.
An interesting topic one that is of great interest to me and Gil of course . Here in Sydney Australia our indications are green at top and read at bottom. Signal indications are changing as trains increase in speed and acceleration. We have introduced turnout repeaters that indicate to a driver that he is apporaching a turnout and must reduce speeds. this signal may be protecting the effected turnout or may be 2 signals in advance of the junction. The reason for these advanced turnout repeaters is due to a derailment that occurred when a driver missed a medium indication (green over yellow) which has 2 definitions. 1. The next signal is at caution (Green over red) 2. Signal is set for tunrout (Yellow over yellow) The driver assumed the next signal was a medium and not a turnout signal and the train went thruogh the points at 100 km/h rather than 25km/h what resulted was a passenger train in the front yard of a hose and spilled al across the road. Thankfully the train was empty at the time and there were no injuries. I will post some pics of the turnout repeater when I can take some shots.
I think that it is pretty common for light signals to have the green aspect on the top, amber in the middle and red on the bottom. Often, operator refer to "pulling" a signal up or a signal being "knocked down", even though the signals are now computer controlled. That refers to the old interlocking machines and the semaphore signals To clear a signal, the operator would have to pull the switches or levers to set the signal and the signal would be "pulled" up. When a train passed a cleared signal, it would trip the release mechanism and the counterweight on the semaphore would cause it to fall back to the stop aspect. Thus as the signal becomes more restrictive, the signal "drops". Also, an operator could knock down a signal by resetting it to stop after the mechanical timer had run, allowing the operator to line another route up and clear or pull up the corresponding signals.
Paul - Is the 1993 "Interim Safeworking Signals Booklet" still in effect or has it been revised. In that there was a combination of route and speed signaling as you told the driver both route and maximum speed authorized. Is that still the case?
