Kensington Signalling Question (Metra Electric)

I have a question about the signals southbound out of Kensington 115th St station. The photo below is a NICTD South Shore train with clearance to cross the ladder track from track 1 to the South Shore Line. Note the top targets are red and the bottom target has four bulbs - the lower right being green.


Would I be right in assuming that the top target would be green for a train cleared to continue south toward University Park on track one and the center target would be green for a train crossing over to track 2? What about the third target? is the lower left light green for a Blue Island train? Or is this used for signaling a train entering the yard south of Kensington? (Or both?)

What are the patterns used here?

The fourth lens on the bottom signal head is lunar white, in order to give a "restricting" indication.

Ah ... a "go really slow" light.

Would that bottom green light be used for BI and yard trains as well? (Did I at least get the use of the top two lights right?)

justalurker66 wrote:Ah ... a "go really slow" light.

Would that bottom green light be used for BI and yard trains as well? (Did I at least get the use of the top two lights right?)

Yes you did, according to my copy of CORA (Chicago Operating Rules Association). The signal indication shown above is known as a "diverging clear", which means trains are cleared to proceed on diverging route at prescribed speed through turnout, both South Shore and Blue Island branch trains will receive this signal on track 1 at Kensington. The lunar aspect is likely for moves into Kensington yard (track becomes yard limits south of the junction to BI, and restricted speeds are in effect), but couldn't confirm that with CORA...

The signal would show a restricting indication for movement into Kensington Yard and also when the tower operator manually requests it (this is called a "call-on") in order to allow a train to follow another train that has not yet cleared the block ahead.

It should be noted that the Metra section of CORA does not apply to the Metra Electric. I've never paid much attention to the signal system on the Electric, but this discussion had gotten me thinking it is probably a "speed" signal system rather than a "route" signal system. If that is the case, red-over-red-over-green would indicate "slow clear," meaning proceed not exceeding "slow" speed through turnouts or interlocking limits. Red-over-green-over-red would indicate "medium clear," meaning proceed not exceeding "medium" speed through turnouts or interlocking limits. (The exact speeds of "slow" and "medium" are defined by operating rules and timetable instructions.) Green-over-red-over-red and red-over-red-over-lunar would still be "clear" and "restricting" respectively. Of course, there are many other aspects possible that are beyond the scope of this discussion.

There are not enough light bulbs to show routing ... so I assume they are using speed based signaling, and the same speed could be called for in the case of several destinations.

Generally speaking, trains staying on the same track with no obstruction should receive a "clear" signal (G R R).
Trains changing tracks through turnouts that can handle "medium speed" (such as high speed crossovers and diverging routes) would receive the "medium clear" signal (R G R).
Trains passing through turnouts that cannot handle "medium speed" would receive a "slow clear" signal (R R G) similar to my photograph above.
Trains allowed to move forward at restricting speed (until next signal) would receive a "restricting" signal (R R W) that I had not considered in my thread starting post.

At this particular signal (end of track 1 southbound at Kensington station) "clear" (G R R) is remaining on track 1 southbound toward University Park (no diverging before next signal). "Medium clear" (R G R) would be used for crossing over to track 2 or the Blue Island / yard lead track (most likely the BI / yard lead). "Slow clear" as photographed is used for crossing over to the ladder track that crosses the CN lines and leads to the South Shore and "upon further review" probably wouldn't be needed for anything else (unless the track 1 to track 2 crossover south of Kensington's platform requires "slow" speed). "Restricting" would be used for the "call on" Mike mentioned, on any track ... most likely clearing the station platform for the next train and stacking trains up on the BI / yard lead. The next signal where the BI diverges from the yard lead (and a train could cross over from any track to BI or the yard) would clear the restriction if it were not itself "restricting".

Or at least that's my thought. Not knowing about existence of the lunar white bulb (dark bulbs are hard to see the color of) threw in the confusion.

BTW: It is interesting to note that southbound to the South Shore gets (R R G) slow clear while northbound from the same track gets (R G R) medium clear (although southbound trains would generally be on track 1 and northbound trains would generally take track 2 missing the crossover south of the platform). The rare northbound to track 1 may get (R R G) slow clear but I have not witnessed it. I expect northbound to the CN freight lines will get the "slow clear" aspect, if not restricting.

Of course, this will change later this year when the second ladder is built to connect the South Shore to track 4 north of Kensington. A big change since CN's track 1 is in the way of such a connection. It will be interesting to see how that will be laid out.

justalurker66 wrote:There are not enough light bulbs to show routing

Everything you wrote makes sense to me except this. If a route-based signal system were in effect, fewer lights would be required here ... green/yellow/red over green/yellow/red/lunar would suffice. Interlockings on route-based signal systems often show the same "diverging clear" indication for multiple routes. One that comes readily to mind is Rondout on the CP/Metra Milwaukee North Line, where westbound trains receive the same red-over-green-over-red aspect when crossing over from one track to the other on the C&M Sub, and when diverging onto the Fox Lake Sub. (The only reason the signals at Rondout have three heads is that the old searchlight mechanisms are limited to three colors each, so the bottom head, with red and lunar lenses, is required for the restricting indication.)

MikeF wrote:

justalurker66 wrote:There are not enough light bulbs to show routing

Everything you wrote makes sense to me except this. If a route-based signal system were in effect, fewer lights would be required here ... green/yellow/red over green/yellow/red/lunar would suffice. Interlockings on route-based signal systems often show the same "diverging clear" indication for multiple routes.

That is where out opinions diverge ... my statement is based on showing EVERY routing without showing the same indication for two routes ... although looking at a track diagram they are pretty limited until the next signal.

A train passing under the signal in the photograph could go five places.
1) Lead track to Blue Island and the yard - next signal is at the turnout that sends trains to the yard or Blue Island
2) Track 1 toward University Park - next signal is at a turnout that could take the train to the yard or Blue Island
3) Track 2 toward University Park - next signal is at a turnout that could take the train back to track 1 (then to the yard or Blue Island)
4) NICTD ladder track to South Shore - Track 1 is normally set as eastbound
5) NICTD ladder track to South Shore - Track 2 (the normal westbound track can be used for eastbounds too)
The sixth destination (the yard) is decided at the next signal down the line.

With green flashing lights I could see how it could be done on three targets, although it might get confusing.
Reusing indications for more than one route would make it easier.

Which brings us to the question ... do Blue Island lead trains get the same "R R G" indication that South Shore trains get or do they get "R G R"? Do trains crossing over from track 1 to track 2 get the expected "R G R" or do they get the South Shore's "R R G" indication (perhaps due to the condition of the crossover). It should be a given that a train remaining on track 1 would get "G R R". The condition of the next signal changing the "G" to "Y" as needed and red-red-lunar white used for all "call-on" requests.

I don't know if the system is the same, but an article was written about the signalling of this junction in the 1950's in F&F a few years back. One of my favorite articles.

http://www.shore-line.org/_pdfs/kensing ... 06_F&F.pdf

That article brings up a good point that relates to justalurker66's statement that in a route-based signal system, each route should have a unique signal aspect: At complex interlockings where it is not possible to display a unique aspect for each route, it is common for the signals to simply show a restricting indication for the more complex routes. (This, of course, places the responsibility on the train crew to observe that the switches are indeed lined for the proper route.)

NICTD uses route based signals (or at least has them in the CORA book). On their two head system diverging or non-diverging routes are easy to note (similar to Metra's CORA listed signals). On the single track section it gets odd as one track approaching the merge "diverts" and the other doesn't. An eastbound train on track 1 can "divert" to the single track (CP 58.1) then "divert" back to track 1 at the next double track segment (CP 54.0). Westbound trains on single track also "divert" to track 2 (the normal westbound track) from single track at CP 47.5 and CP 37.9 (although 37.9 is a passing track where a westbound could stay on track 1 as long as nothing was conflicting). It looks like whomever set up the route assumed there was a second track for the entire length.

Where it gets challenging is when there is more than one diversion route. NICTD has a "Diverging Clear Approach Diverging" (Red over flashing green) that would allow for a second diverging route before the next signal. Metra has their "Diverging Approach Diverging" (R Y Y) but that expect the second diverging at the next signal. The challenge of having a separate "diverge left" or "diverge right" isn't met without the third head. But combining NICTD's flashing green with a third head could open up extra possibilities (R G R, R fG R, R R G, R R fG) --- but as noted it could get confusing.

I think you're confused on the meaning of NICTD's "diverging clear approach diverging." It carries exactly the same indication as Metra's "diverging approach diverging" -- "Proceed on diverging route at prescribed speed through turnout prepared to proceed on diverging route at next signal at prescribed speed through turnout."

I can't say I've ever seen a signal system with "diverge left" and "diverge right" indications. Can you cite an example?

MikeF wrote:I think you're confused on the meaning of NICTD's "diverging clear approach diverging." It carries exactly the same indication as Metra's "diverging approach diverging" -- "Proceed on diverging route at prescribed speed through turnout prepared to proceed on diverging route at next signal at prescribed speed through turnout."

Oops ... I misread that. Going back to the source (for me, Oct 2007 CORA) you are correct.

I can't say I've ever seen a signal system with "diverge left" and "diverge right" indications. Can you cite an example?

Not specifically ... I reckon that on a three headed system the second head is for diverging onto the second main (crossing over) and the third head is for going somewhere else (either across the second main to a siding or to a siding on the opposite side of the main the train is on). In essence, at Kensington track 1 the second head could indicate "diverge left" to track 2 with the third head being "diverge right" to the BI/yard lead. (Although at Kensington "diverge far left" uses that third head.) Still following the idea of 1=go straight 2=go to other main 3=go elsewhere with all the elsewhere's sharing.

Although it apparently isn't set up this way, it wouldn't be a big deal for SS trains go get a Restricting to go to the SS line. Said line has an "entrance" signal immediately east/south of the plant. This way, the third signal head could be reserved for BI branch trains. (But then, is the BI branch even signaled, or does it just run by timetable authority/train orders? This is kind of how the Rondout-Fox Lake line works.)

My only experiences with Kensington have been with with CNIC mains #1 and 2, running on Amtrak CHI-CDL corridor. The whole place is quite a quagmire and apart from those two tracks I really have no idea how the rest of the signals are set up.

I prefer the idea of using Restricting only for "call-on" or other truly restricting needs. I could see using Restricting on a regular basis for a yard entrance but not for a main or branch line (although it seems that it is used that way in other Metra places).

It is probably good enough that the South Shore and Blue Island trains share the "R R G" aspect. Engineers just have to trust the interlocking operator not to send a train the wrong way. Fortunately if they do both lines are electrified and can handle the train sizes used so once the train cleared the interlocking in could be brought back to Kensington and routed properly. It is also pretty clear looking at the first switch south of the platform if the train is going "left" to the South Shore or straight to the next switch in the interlocking where it would go "right" to Blue Island. If route based signals were shared between "cross to track 2" and "South Shore" the engineer wouldn't know until they saw the second switch on track 2 if they were going the right place (a switch that I believe cannot be seen from the platform stop location before the signal).

Flashing the third head would be the only way I could see making a three head signal 99% effective in giving the route (100% would not be gained unless there was a signal difference between "go to NICTD track 1" and "go to NICTD track 2" ... but "go to NICTD" is good enough since no train would take track 2 unless there was an emergency or track maintenance reason). The "entrance" signal is only on track 1 (full CTC signal). Track 2 has an out of service dwarf signal and is ABS until the next CP. Generally, only freights would take track 2, coming from the CN.

FYI: Blue Island is signaled.
BTW: There are changes coming by the end of the year at Kensington Interlocking that should be interesting. I have not seen the plan but NICTD is reporting that an agreement has been reached between Metra, CN and NICTD to build a second connection across the CN that would connect directly to Metra's track 4 north of Kensington station. With no space between CN's track 1 and Metra's track 2 at Kensington station this should be an interesting connection. I'm looking forward to seeing a diagram and (more importantly) seeing it in action.