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Discussion Starter #1
Hi,

I don't know much about prototype rail operation. (please be nice..)

When reading about signals -
I see signals for occupied blocks and routes. (Mast signals, and dwarf signals) Are there any signals for turnout position?
The only thing I have seen is what looks like a dwarf signal, but instead of lights- they have painted metal tabs.

On model layouts - most seem to use software or fascia-mounted LEDs to indicate turnout position.

Do we use anything beside the actual turnouts on the layout? (that looks prototypical)
Also - what would be the prototypical placement of these in relation to the switch - right at the throwbar?

How do prototype trains know what position an upcoming turnout is set to, and how far in advance of the turnout do they know? (1950s to 1970s era...)
 

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mainline turnouts are aligned for the train by a tower or dispatcher (e.g. CTC). The signal indicates indicates Stop or the speed to proceed at. The signal needs to be positioned far enough ahead of the turnout for the train to stop

manually operated spur switches may have mechanically turned colored plates to indicate turnout position
 

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Discussion Starter #3
So for switches that don't have the colored plates, the engineer is just trusting dispatch, or someone on the ground?

Sent from my LM-V450 using Tapatalk
 

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outside of a terminal, there may be pad locks on the switches or electrically operated locks controlled by the dispatcher (CTC).

there can be a locked manually operated turnout on the mainline. It's not possible for the engineer to see the position of the turnout and stop the train in time if it were incorrect.
 

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outside of a terminal, there may be pad locks on the switches or electrically operated locks controlled by the dispatcher (CTC).

there can be a locked manually operated turnout on the mainline. It's not possible for the engineer to see the position of the turnout and stop the train in time if it were incorrect.
Greg

Wouldn't a turnout on a main line with points set to divert activate the
signal system. Would that not be a warning to oncoming trains?

Don
 

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Don
My understanding is there is no need for a manually operated turnout on the mainline to be tied into the signal system because the block could be blocked by the dispatcher while the crew is given time to switch the spur and no trains should be scheduled on that route at that time

if the turnout is electrically locked, my guess is the fact that it is unlocked, could cause the signal to be set.
 

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Don
My understanding is there is no need for a manually operated turnout on the mainline to be tied into the signal system because the block could be blocked by the dispatcher while the crew is given time to switch the spur and no trains should be scheduled on that route at that time

if the turnout is electrically locked, my guess is the fact that it is unlocked, could cause the signal to be set.
Some what pertinent, you recall, last year, or year before, there was a disasterous
Amtrak/CSX crash because a switch crew had failed to throw the points on a main
turnout and the signal system had been deactivated for some sort of work. With
no warning track side signal, the Amtrak crashed head on into the standing freight
at full speed.

Don
 

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Don't forget that there is verbal radio communication to-from cabs, towers and stations. In the old days a message to an engineer was telegraphed from a tower to next station or tower that train will be stopping at...Or, the train was actually flagged down in dark territory (unsignaled trackage) or with lanterns or flares at night. (4-4-0 and 4-6-0) engines ran way way slower in those times, and had only 7-8 short, wooden cars, and so could hunker down in time for the flag/lantern man ( with orders for train to go no further due to say, a washed out bridge ahead or an avalanche)...
As gregc says, the switches with metal tabs are thrown by hand in yards or at spur tracks.. I believe many passing sidings are manual as well..But many are for high speed passenger lines and aligned remotely by a tower or by Central Traffic Control (CTC)....
 

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Hi,

I don't know much about prototype rail operation. (please be nice..)

When reading about signals -
I see signals for occupied blocks and routes. (Mast signals, and dwarf signals) Are there any signals for turnout position?
The only thing I have seen is what looks like a dwarf signal, but instead of lights- they have painted metal tabs.
Switches that are hand-thrown by a train crew have a coloured metal target attached to the switch stand that rotates along with the control mechanism. This will show a red or yellow (depending on whether it's a main track or other track switch) at right angles to the track when "reversed" and this target will be parallel to the track when the switch is in "normal" (straight-through) position. A lot of switches may also have a small green target that shows at right angles to the track in "normal" position as well.

A collection of sample switch stands from Google image search:



A train crew travelling down a track will be able to see these targets very clearly since they're aligned down the track. Since the mechanism is attached to the throw bar of the switch, that's where the indicator targets are.

Any switches on signalled tracks will also influence the signal system.

If a switch is remotely controlled by tower operator or CTC dispatcher, then it will be part of an interlocking or control point and protected by signals. The signals don't just tell you the position of the switch(es) per se, but that does factor in. Generally speaking, there two approaches to railroad signalling in North America - "route signalling" and "speed signalling". Different railroads have their own rulebooks of what the different combinations of signal lights mean, but there are a few "universal" rules:
  • signals are located at the exact point where they apply (i.e. before the point where a train would need to safely stop for a "Stop" signal).
  • each signal applies only to one track
  • each signal is read as a whole, with the specific combination of lights giving the meaning. Do NOT believe anyone that says "the top light applies to the main track, the bottom light for the siding".... while in many situations it may appear to work out, that's an over simplification that is not actually accurate.
"Route" signalling is a bit simpler, where different signal indications will either give you "Clear" (straight through) or "Diverging" (obvious) indications, to indicate whether a train is to take a diverging route. Speed through turnouts is dictated by local knowledge of the timetable and physical speed restrictions.

"Speed" signalling used on many railroads gives different indications for "Clear" and specific speeds - "Slow" (15 MPH), "Medium" (30 MPH), "Limited" (45 MPH). The signal system will be designed to give the proper speed indication to match the design rating of the turnouts.

In the case of a simple passing siding, the signal indication will make it very obvious which track you're going into. In the case of much more complicated junctions and crossovers between multiple tracks, there could be many different routes that would all get the same speed indication, but that's all the crew really needs. (The whole set of signals and switches will be interlocked together so only safe movements can be made.)

Signals basically take into account three pieces of information:
  • position of any switches
  • occupancy of the block ahead
  • indication of the next signal (some simplified explanations will say "the next two blocks" but that's not really accurate, since the next signal could be "Stop" at an interlocking with no other trains occupying track, or you could be getting something like an "Approach Slow" telling you that you'll need to pass the next signal at Slow speed through diverging turnouts.
You don't generally have separate signals for blocks and switches - all of this information is actually tied into the signal system.

This obviously only skims the surface; signal system logic is a whole topic and field to itself.

On model layouts - most seem to use software or fascia-mounted LEDs to indicate turnout position.

Do we use anything beside the actual turnouts on the layout? (that looks prototypical)
Also - what would be the prototypical placement of these in relation to the switch - right at the throwbar?
Some people have done:
  • nothing, just view the points
  • for switches with manual throws put a dab of green/red/yellow paint on the handle to make it clear which way its thrown (like this Caboose Industries throw https://users.frii.com/gbooth/Trains/GreatWestern/TipsAndTricks/EasyGroundThrows/nail.jpg)
  • actual model rotating switch stand targets (fine detail, can be finicky to install) linked to the turnout throw bar
  • indicator lights on a fascia panel
  • signals on the layout that simply indicate the turnout's position (not really prototypical signals)
  • full realistic CTC or ABS type signalling that takes block occupancy and turnout positions into account
How do prototype trains know what position an upcoming turnout is set to, and how far in advance of the turnout do they know? (1950s to 1970s era...)
See above.

For hand-thrown turnouts on non-signalled tracks, it'll be when the switch stand target comes into view.

For signalled tracks, the block signals will give advance warning of the next signal down. e.g. let's say you're on single track coming up to a split into two tracks. At the split, the signal is showing something like "Slow Clear" (in many rulebooks this would be a Red over Green), indicating a reduced speed move through diverging switches. The last block signal a mile or two in advanced of the split would show an indication that means "Approach Slow" (Yellow over Yellow in some rulebooks) telling you the next signal has a "Slow" indication. If movement at the split was lined for the straight track, both signals would be showing "Clear" (Green over Red).
 

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We lived in Fostoria, near where the NKP and B&O tracks crossed and it was not unusual for track torpedos to sound at night. Just another sound one could model!
 

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@cv_acr -- I'm curious about the yellow flag signal in your google pic. Does anyone know a time period for this type (it looks like it might fit in a late 1800's layout)? I assume the flag goes up when the turnout is thrown in the diverging position?

From cv_acr's answer above, here's my own build of a working signal in HO scale. It's pretty solid, but yeah it was a pain to make.
539933


The actual mechanism is just a rotating tab with some wire through it. The distance between the two holes in the tab are the same as the distance traveled by the points between positions, which works out to give me a 90-degree rotation of the flag.
539934
 

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@cv_acr -- I'm curious about the yellow flag signal in your google pic. Does anyone know a time period for this type (it looks like it might fit in a late 1800's layout)? I assume the flag goes up when the turnout is thrown in the diverging position?
I've never actually seen one like that before. It's probably older, and probably unique to a particular railroad.

Since it seems to replicate a small semaphore signal, and semaphore blades were usually straight up for "clear" and horizontal for "stop" i'd guess that it would be down when the switch is in the diverging position.

But I've never seen one like it and not sure what railroad it's from.
 
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