Passenger Trains > CN / IC signal question

Living not far away, I often bike over to CN/IC to watch Amtrak trains go through Matteson.  Usually I will go up to the Matteson Metra platform to view northbounds and to the 211th St.platform for southbounds.  I usually have my eye on the signal for track 1 by the crossover to track 2 for the EJ&E junction, north of the Matteson platform for northbounds and the southbound one is visible looking south from 211.  (Supplemented by ATCS monitor running on a remote PC I can connect to.)

So this afternoon I get up to 211th awaiting 393 the Illini.  Looking south the the crossover signal and expecting green over red instead it was yellow over flashing red.  I've never seen that before.  Had I just missed a freight that used the crossover which was not yet re-aligned?  Anyway, it changed to flashing yellow over solid red and finally clear (green over red).

Please enlighten.

Yellow over Flashing Red is "Approach Restricting" in the CN rulebook. The next signal would be Restricting which is (basically) cleared by the dispatcher (if the next signal was a CP) but the track ahead of that second signal would be blocked or have a switch open or broken rail or other reason why the train would need to travel under a Restricting aspect (most likely just occupied).

Once the train two blocks ahead cleared that signal would change and the signal you saw would no longer be Approach Restricting. The Flashing Yellow over Red aspect is Advance Approach which means the second signal should then be Approach (yellow over red).

Thanks, Lurker. But does “ahead” change with the switch setting? Just wondering if I was seeing it before the switch was realigned and it was showing me the condition of the diverging route. The switch beyond the signal crosses SB’s over to 2 and just beyond that is a switch to the EJ&E connector. A few hundred feet further is a crossover between the two connectors. Stay the course to go east; cross over to go west.

filmteknik Wrote:
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> Thanks, Lurker. But does “ahead” change with
> the switch setting? Just wondering if I was seeing
> it before the switch was realigned and it was
> showing me the condition of the diverging route.
> The switch beyond the signal crosses SB’s over
> to 2 and just beyond that is a switch to the EJ&E
> connector. A few hundred feet further is a
> crossover between the two connectors. Stay the
> course to go east; cross over to go west.

Both trains and other track conditions will affect signal indications....but signals will only reflect absolute conditions....the track immediately ahead is unavailable for any speed (you get Stop or Restricting) but the signal itself doesn't say WHY you cannot proceed....it's probably the train ahead but it may also be the switch ahead is not ready....or both....if the track is not available two blocks ahead you get a more permissive signal such as Advanced Approach, or Approach Medium....or something....but again the exact reason the track is unavailable two blocks ahead is not directly determined by signal indication. You just take it for what indicates and you comply....and if you are aware of what's going on around you, you may make educated guesses of what's going on ahead...but you do not self dispatch....you just comply with what you see with your eyes. What does ahead mean? It depends on what is is......

In my opinion, "Approach Restricting" is a very dangerous indication and sets a trap for the locomotive engineer.  The definition of Restricted Speed includes the requirement to be able to stop within half the range of vision.  A DS or operator could cause a Restricting indication to be displayed without knowing there was a broken rail, washout, or other impediment five feet beyond the signal.  Approach requires being prepared to stop at the next signal, not to be required to stop if the next signal displays other than Stop or Stop and Proceed.  I don't see how a locomotive engineer, complying fully with the rules, will handle his/her train any differently having passed a flat Approach indication than having passed an Approach Restricting -- the difference is only whether you have to be prepared to stop in front of the signal or immediately past it.

I'd really be interested in hearing from some of the hoggers out there.

Gordon



Edited 1 time(s). Last edit at 07/10/20 16:42 by gbmott.

gbmott Wrote:
-------------------------------------------------------
> In my opinion, "Approach Restricting" is a very
> dangerous indication and sets a trap for the
> locomotive engineer.  The definition of
> Restricted Speed includes the requirement to be
> able to stop within half the range of vision.  A
> DS or operator could cause a Restricting
> indication to be displayed without knowing there
> was a broken rail, washout, or other impediment
> five feet beyond the signal.  Approach requires
> being prepared to stop at the next signal, not to
> be required to stop if the next signal displays
> other than Stop or Stop and Proceed.  I don't see
> how a locomotive engineer, complying full with the
> rules, will handle his/her train any differently
> having passed a flat Approach indication than
> having passed an Approach Restricting -- the
> difference is only whether you have to be prepared
> to stop in front of the signal or immediately past
> it.
>
> I'd really be interested in hearing from some of
> the hoggers out there.
>
> Gordon

You do take Approach Restricting prepared to Stop at the NEXT signal....if upon reaching the next signal you find that a Restricted route is available and you can see ahead far enough to move ahead you do so....but always ready to stop in HALF the range of vision...or less distance if you can...the actual conditions determining your handling. But no you cannot trap a competent engineer in any way shape or form....he ALWAYS knows when the conditions may require a stop and he is ready for it ALWAYS......this is not just a matter of pride...it's life and death and requires our respect, and we give it. 

filmteknik Wrote:
-------------------------------------------------------
> Thanks, Lurker. But does “ahead” change with the switch setting?

Yes, as the others mentioned. The signal displayed will be based on the combination of track conditions and dispatcher cleared signals.

> Just wondering if I was seeing it before the switch was realigned and it was showing me the condition of the diverging route.
> The switch beyond the signal crosses SB’s over to 2 and just beyond that is a switch to the EJ&E connector.

The Approach Restricting would reflect the next signal down the track being restricting. The dispatcher would not be able to change the switch at the interlocking if he has a signal cleared through that switch. The signal at the interlocking would need to change to stop and have a time out run before the dispacher would be able to change the switch and clear a new route. That is not the sequence you reported.

I will try to clarify my question about what does ahead mean.

If there is a switch and it’s lined to a route where there is something up ahead, the signal before that switch is going to show something less than clear, whether approach or restricting or even stop, or whatever, depending on how many blocks ahead the occupied block is.

The dispatcher realigns the switch.

This other route is devoid of any trains (or errant switches or broken rails). Does the signal immediately go to clear? As well as prior signals.

If the dispatcher changes their mind and moves the switch back, I presume the signal goes back to indicating conditions ahead on that route. So we’re always being alerted to what’s ahead even as “ahead” changes.

And in that case I presume it would also reflect subsequent switch alignments. Whatever route a train will take the signals is warning of conditions on that route.

So in the case I asked about there could be 4 possible “what’s ahead” scenarios for a SB on track 1.

1. Stay on 1.
2. Cross over to 2 and stay on 2.
3. Cross over to 2 then branch onto the J connector. End up EB on the J.
4. Cross over to 2, branch onto J connector, go thru crossover to other J connector. End up WB on the J.

I’m guessing the route straight south on 1 was clear but the signal was still showing conditions ahead for the route (2 or 3 or 4) taken by a freight.

There is something else I've been wondering about in this area, if anyone knows the explanation. North of Homewood, there is very little traffic on the double track main, particularly with one of the Amtrak round trips cut. If a freight is running from 16th St. To Matteson, it often is the only train. At 16th St. It has to be on Main 1, and it'll often be lined on Main 1 at Matteson. Traffic is also frequently parked on Main 2 at Homewood, so it has to be Main 1 past there. Yet nearly everytime, it is lined onto Main 2 between Cermak and Kensington or thereabouts, which adds in a slower speed crossover, depending on which is used. This is so frequent that it's as if there is a rule that a freight has to run in Main 2. Yet, to be clear, there is almost never any opposing move that would prompt that, when it could just use Main 1. Does anyone know why that is?

justalurker66 Wrote:
-------------------------------------------------------
> The Approach Restricting would reflect the next
> signal down the track being restricting. The
> dispatcher would not be able to change the switch
> at the interlocking if he has a signal cleared
> through that switch. The signal at the
> interlocking would need to change to Stop and have
> a time out run before the dispacher would be able
> to change the switch and clear a new route. That
> is not the sequence you reported.

Bingo.

The scenario discussed here is the first time I've ever heard of Approach Restricting as a mainline signal aspect. Its purpose seems to be to tell an engineer, "You have a route at the home signal you will see next, but for now it's at Restricted speed." In that regard it's slightly more favorable than Approach - but only slightly, because the granted route could be occupied just beyond interlocking limits.

In the NORAC rules that I grew up with, Approach Restricting was the fixed yellow in dark territory indicating a signal somewhere beyond it that could be displaying Stop. But this would not be the first example I've heard about with CN having unique aspects on its former U.S. lines that strongly resemble longer-standing Canadian signal rules.

Edited to add after some brief research: Illinois Central used to use lunar white for Restricting, but several decades ago started replacing that with flashing red at many locations, so R/>R< or R/R/>R< became Restricting. After CN took over, it went one step further and introduced this Y/>R< aspect as basically a distant signal for a Restricting, along with replacing all of the lunar white that IC hadn't gotten to yet at home signals.

 



Edited 1 time(s). Last edit at 07/11/20 10:32 by toledopatch.

filmteknik Wrote:
-------------------------------------------------------
> If there is a switch and it’s lined to a route where there is something up ahead, the signal before
> that switch is going to show something less than clear, whether approach or restricting or even
> stop, or whatever, depending on how many blocks ahead the occupied block is.

Are you referring to the signal AT the switch (entering the interlocking plant where the switch and signal exists)?

In general the signal at the interlocking will show:
* STOP if the dispatcher has not cleared a route for the track controlled by the signal.
* STOP if the path through the interlocking is not clear (sense occupied).
* RESTRICTING if the dispatcher has cleared a path but the track beyond the interlocking is not clear.
* APPROACH if the dispatcher has cleared a path, the track between the interlocking and the next signal is clear but the track beyond the next signal is not clear (or the next signal is an interlocking that is not clear).
Approach can have several variations, such as the "Approach Restricting" you saw or "Approach Medium" or "Approach Diverging" etc. The concept is to tell the train crew what the next signal will be.
* ADVANCE APPROACH is offered on some railroads if the next two signal blocks are clear (but the third isn't). I think of it as an "approach approach" since it tells the crew they are approaching an approach signal. Calling it an Approach Approach is not accurate.
* CLEAR if the dispatcher has cleared a path and there is no occupancy or other reason to slow down detected within the next two blocks (next three if Advance Approach is used).

Adding confusion, the signaling system will also look at the switches and display different signals depending on how those signals are set.

On a "speed signaled" railroad the signaling system will reflect a reduced speed if a train will be taking a diverging route through a turnout. Moving from track 1 to track 2 in most cases will present a "Medium" speed signal (Medium Clear, Medium Approach, etc) in a speed signal railroad. Medium is a speed limit of 30 MPH until the entire train clears the turnout. If the railroad has put in a slow speed turnout a "Slow" speed signal will be presented (15 MPH). If the railroad has put in a 45 MPH turnout a "Limited" speed signal will be presented. The speed limit applies until the tail end of the train passes the interlocking.

On a "route signaled" railroad the signaling system will reflect the route the train will be taking (without suggesting a speed limit) through a turnout. Moving from track 1 to track 2 will present a "Diverging" route signal (Diverging Clear, Diverging Approach, etc) on a route signaled railroad. Without a speed reflected the crew needs to know their crossover speed limits. (Not that all crews should not already know every crossover and speed limit, but the signals do not present a reminder. Diverging Clear just means that the train is routed to another track - not what the speed limit is while crossing over. The speed based signals give a speed not a route.)

If I recall correctly, CN-IC is route based ... so you would see an Approach Diverging signal (yellow over yellow) one signal before a Diverging signal.

> The dispatcher realigns the switch.
> This other route is devoid of any trains (or errant switches or broken rails). Does the signal immediately go to clear?

You are missing the step where the dispatcher has to take away the path through the switch. The dispatcher cannot realign a switch when a path is cleared through.

> If the dispatcher changes their mind and moves the switch back, I presume the signal goes back to indicating
> conditions ahead on that route. So we’re always being alerted to what’s ahead even as “ahead” changes.

True. But that important step where the signal goes back to STOP when a dispatcher changes their mind cannot be ignored or forgotten.
The signal you saw would need to change to STOP before the route was changed at the interlocking that signal protects.
The signal you saw would have changed to APPROACH (from approach restricting) if the dispatcher took away the next signal to make changes there.
What you saw was track occupancy changing.



Edited 1 time(s). Last edit at 07/11/20 22:19 by justalurker66.

toledopatch Wrote:
-------------------------------------------------------
> Illinois Central used to use lunar white for Restricting,

CN-IC used route based signaling ... diverging signals for changing tracks. With a complicated plant displaying all of the routes could get complicated so the signal displays were simplified. An interlocking with two diverging routes would normally have three heads to reflect the three options. But the IC had the habit of using Lunar for anything that they didn't want to add a head for or if they ran out of heads.

The nominal use of the top head was for trains not changing tracks (clear, approach), the second head for trains changing tracks (diverging clear, diverging approach) and a third head for trains taking another route (still called diverging clear and diverging approach but the third head being an indication to the crew that the route was not the same as the second head). The use of Lunar would allow the train to pass through the interlocking to some route without a dedicated signal pattern (perhaps to run against the current of traffic back when there was one).

If I recall correctly IC used Lunar for the CSS&SB trains southbound at Kensington ... clearance to move but watch to make sure all the switches are where you want to go.
Lunar was also used as a "call on" signal (basically Restricting in modern terms) where a train can pull up and stop behind a train occupying the track ahead.
 

In the real railroad world an Approach signal will often
cause the engineer to stop the train hundreds if not thousands
of feet before the next signal if the next signal is an absolute signal.

Not required to stop there by operating rules but to keep from blocking
grade crossings.  

Normally a Restricting is the most favorable signal that can be displayed at a control point
when the route is lined into a track outside the signal system such as a yard
track, running track or non-bonded siding.

Where preview of the CP signal is hidden by curvature, grade, etc, an Approach
Restricting on the signal prior to the CP gives the engineer the info that he/she is
lined up at the CP.  The engineer then knows to continue towards the CP, contacting
the yardmaster for instructions, etc 

Without the Approach Restricting the engineer would be engaged in the often
fruitless task of toning up the DS to find out what is going on.  The train would probably
be stopped short of the road crossings before the DS ever answered. 

gbmott Wrote:
-------------------------------------------------------
> In my opinion, "Approach Restricting" is a very
> dangerous indication and sets a trap for the
> locomotive engineer.  The definition of
> Restricted Speed includes the requirement to be
> able to stop within half the range of vision.  A
> DS or operator could cause a Restricting
> indication to be displayed without knowing there
> was a broken rail, washout, or other impediment
> five feet beyond the signal.  Approach requires
> being prepared to stop at the next signal, not to
> be required to stop if the next signal displays
> other than Stop or Stop and Proceed.  I don't see
> how a locomotive engineer, complying fully with
> the rules, will handle his/her train any
> differently having passed a flat Approach
> indication than having passed an Approach
> Restricting -- the difference is only whether you
> have to be prepared to stop in front of the signal
> or immediately past it.
>
> I'd really be interested in hearing from some of
> the hoggers out there.
>
> Gordon

gbmott Wrote:
-------------------------------------------------------
>  A DS or operator could cause a Restricting indication to be displayed without knowing
> there was a broken rail, washout, or other impediment five feet beyond the signal.

A dispatcher/operator does not set aspects. They set routes and clear signals to follow the routes. The signaling system determines the aspect displayed based on track conditions (including the dispatcher's cleared route). (A cleared route is not the same as a "CLEAR" indication. It is a way to refer to a route where the dispatcher has given their permission for a train to move, not the aspect displayed.)

Dispatchers set routes in to occupied track daily and often throghout the day. There is a "fleet" function that can be used to automatically set a signal to clear as soon as a train has passed.
It is up to the signaling system to detect occupancy and track problems and determine what aspects are displayed.

I took a closer look at the track layout -
The signal in question is Track 1 at CP Swede. There is a left hand crossover from Track 1 to (per timetable) Track 3 then a left hand turnout to the connector track outside loop on Track 3. (A trailing right hand turnout connects the inside loop connector track to Track 3 and thus ends Swede on the CN-IC. There is also a right hand crossover between the outside and inside loop which would allow a southbound train to head west on the EJ&E. CP Lowe is the EJ&E end of the loop and would be the next interlocking for trains routed on the connector tracks.)

Track 1 continues south to CP 67th St (Stuenkel) where the CN-IC becomes single track.
There is an intermediate signal (not dispatcher controlled) between the two interlockings.

Approach Restricting in this case would reflect the intermediate signal ahead displaying Restricting (an intermediate signal's most restrictive aspect).
One would see the Approach Restricting aspect on Track 1 southbound at Swede if the intermediate signal was "Restricting" (generally, a train south of the intermediate).
The intermediate signal would change to approach when the train cleared Stuenkel and the signal at Swede would change to Advance Approach, as observed.