- MP 000 -> MP 067 - Pennsylvania Railroad - Relay + Electromechanical - 1940s
- MP 067 -> MP 104 - Amtrak - Solid State - 2008
- MP 105 -> MP 231 - Conrail - Solid State (GE Series 6) + Relay - 1990
- MP 231 -> MP 237 - Pennsylvania Railroad - Relay (US&S 504 CTC) + Electromechanical - 1950s
- MP 237 -> MP 265 - Conrail - Solid State (GE Series 6) + Relay - 1994
- MP 265 -> MP 274 - Norfolk Southern - Solid State - 2000
- MP 274 -> MP 290 - Conrail - Relay (no interlockings) - 1990
- MP 290 -> MP 353 - Conrail - Relay(? Listed as D601 system) - 1980
Not sure what conclusions can really be drawn here, but as we pass Johnstown we enter into the earliest of the re-signaling projects that was intended to replace the original PRR signaling. The Pittsburgh Division interlocking charts indexed at Multimodal Ways list the interlocking system used in this section as D601 (details of which I was unable to locate) and the interlocking sheets are the last series of which were hand drafted. I suspect this is a late model of all-relay based CTC technology that first became popular in the 1950's and was eventually supplanted by the new SSI systems in the 1980's.
One side effect of being an early adopter was that none of the PRR signal bridges were replaced with Position Light mast signals. In 1980 railroads still had many first generation road switchers in service and they were designed to run long-hood forward so signals still had to be mounted to the right of the track (Engineer's Side). This meant either gantries or tall bracket masts were needed on double track CTC lines. The downside of this is that between MP 290 and MP 353 there has been significant attrition of position lights because by the time the gantries finally became life expired Conrail has stopped installing position light mast signals to replace gantries like they had between MP 105 and MP 231.
We begin our journey at Johnstown on a new track diagram, but still in three track territory.
Past CP-C we come to CP-JW, which used to be remote C tower with direct wire control from C's Model 14 machine. CP-JW was re-signaled when C tower was closed and had all new signals installed. Like CP-AO, CP-JW is on track 1 only and provides access to the Johnstown yard and helper base from the west. As such there is a power split point derail on the yard track. The signal on the main track is an innovative model that allows the whole signal head unit to be cranked down to ground level for servicing. While this saves on maintainers having to climb the ladder, it requires that the signal be taken out of service, a complicated process that involves the dispatcher and transmitting paperwork to trains. Simply working on a traditional signal will simply result in a dark head, which is covered by standard rules. The yard track has a simple 3-stack Safetran modular dwarf signal that can display 1 or 2 lamp combinations.
I should mention here that when Conrail re-signaled the lines it was more likely to connect the existing interlocking appliances and signals to the new vital logic controllers. Today most railroads prefer to install brand new signals and get all the testing out of the way before taking the old signals out of service and placing the new ones in service in one go. In a literal cut-over the interlocking would have extended downtime to test all of the splices were done properly. CP-C and CP-JW were both re-signaled in this new fashion.
The new relay hut was placed directly adjacent to the old one. It looks like in 2003 someone was still producing new Conrail style ID boards.
A traditional mast signal was erected at the west end of the interlocking in the new NS "tombstone" variety. The switch at CP-JW leads to unsignaled territory, but CP-JW is also the track 1 distant to CP-C and grants a lower head green lamp for Approach Medium aspects.
Just past the Johnstown Amtrak station we pass the 2752E signal mounted on a late model PRR gantry. The position light signals on this bridge apply to track 2 only and it is the eastbound distant to CP-C on track 2. This section of the line had its block signals refreshed by Conrail in the 1990's so their style of re-numbering applies. I should also point out that while this looks like a normal three track line, track three on the left is not like the others. It will diverge from tracks 1 and 2 and cross the Conemaugh River to run down the other side to CP-CONPIT. Singles lines with tracks that take different paths from point A to point B is not a unique occurrence and such routes are often called Slow Routes or Turkey Paths. In this case the time penalty for a track 3 routing is 15 minutes and every so often this train suffers the hit then tracks 1 and 2 develop blockages.
Also note where the second island platform for the Johnstown station used to sit.
The MP 277 automatic is a Conrail install consisting of a Cantilever covering tracks 1 and 2 and a mast for track 3. This is the distant for CP-C on track 3 so track 3 has one less block in this segment than 1 and 2 do. From the footings these signals replaced a PRR signal bridge at the same location which used to be part of SG tower which provided the final decision point for movements into t3k or the Sang Hollow Extension as it was known at the time.
After several additional floods in the 20th Century the Army Corps of Engineers decided to pot an end to the problem by applying appropriate protections to the riverbank .
We are once again treated to position light masts installed in the 1990 refresh for the MP 280 automatic.
More PLs at MP 283. The rail line is now traversing the Conemaugh River gap through a thick mountain ridge and there are no adjacent road lines or settlements.
The MP 286 automatics are co-located with an AEI tag reader and the "New Florance" Hotbox/Dragging Equipment detector. This is the westbound distant to CP-CONPIT
CP-CONPIT is an important junction between the Pittsburgh Line and the Conemaugh Line (hence the name). The Conemaugh Line is a low-grade route that follows the Conemaugh River to the Allegheny River and then down into Pittsburgh. The Pittsburgh Line will cut overland to Pittsburgh directly. The westbound mast signals on tracks 1 and 2 are Position Light and mount early examples of the 'C' Board you might remember from Amtrak's re-signaled Harrisburg Line. The Conemaugh Line was the PRR's experimental installation of cab-signal only operation in the late 1940's between here and CP-KISKI where the line reaches the Allegheny River. It took another 4 decades for cab signal only operation to be expanded my Conrail to some of the PRR's other former routes.
Also notice that a new EMD SD70M-2 is waiting on track 3 with a mixed freight train.
Here is the replacement mast wb color light mast signal on Pittsburgh Line tk3, which replaced a 1970's era single track position light gantry. The 17 switch along with an air compressor and air line are visible on the left.
This interlocking exists from PRR Days when tk3 was known as the Sang Hollow Extension, only back then the interlocking was called JD and was quite a bit more complex. Today CP-CONPIT resembles a typical 3-track full crossover, only with the turnouts to the 3rd track being comically long, however switch and signal numbers that reach the high double digits hint at its previous complexity. Here we see the 15 switch after the long crossover from the 17 switch.
The 11 switch is regular size. I suspect that the first wave of re-signaling on the Main Line occurred on the Middle Division between MP 105 and MP 231. This is where the tracks were reduced from 3 and 4 with the center track being bi-directional with towers staying open and would have taken place in the early or mid 1970's. By 1980 the technology and political will had developed to take the plunge into CTC replacing the entire PRR block system between here and Pittsburgh. 10 years later the same was carried out on the Middle Division with updated technology.
A radio base station sits in the middle of the interlocking while the unpainted Aluminum relay hut on the right provides further evidence that the signaling in this interlocking is not like the others we have come to know with their Corten steel shacks. Here we see the 9 and 7 switches and no that cooling tower is only for a coal power plant.
This interlocking is a bit of an Even Steven as tracks 1 and 2 are position light westbound and color light eastbound while track 3 is the opposite.
The 1970's slab steel gantry over the Conemaugh Line track was clearly built for 2 tracks, but today only has one. I believe a matching gantry was on the east end over track 3, but was replaced by the color light mast. Note the MP 0 sign marking the start of the Conemaugh Line.
Here is a fun long shot of the eastbound signals at CP-CONPIT with several powerplant stacks in the background. There is a bit of traffic congestion in evidence as you can see the train on track 3 waiting and my train just passed through, but there is another train lined on track 1 and not yet apparent is a 4th train eastbound on the single track Conemaugh Line. When it rains it pours on North American railroads and mile long freight trains take a while to clear your interlocking plant.
Note the sign promoting the change in safety district.
Here is the 2928 automatic with that eb stack train on track 1 that I mentioned. Note that we are now back in to traditional PRR signal numbering. You might have noticed that between MP 105 and MP 231 all of the relay cabinets at block signals were Corten steel huts dating from the 1990 re-signaling. As between MP 237 and MP 265 we have returned to the mild steel cabinets, which means that the block signaling logic is still as it was back in PRR times.
Oh, here's that 4th train I mentioned inbound on the Conemaugh Line. I did not know how the dispatcher was going to sort this all out.
Automatic 2946. Like I said no PL masts in this segment. As the PRR gantries gave out in the 90's they were replaced with color lights.
Automatic 2964. More color lights, but the cabinets are original.
Automatic 2982. These were installed in the early NS era c.2000 where the local C&S department were still committed to target style color lights instead of traffic lights used elsewhere on NS. Still they had to buy from the corporate Safetran catalogue tho as you can tell by the layout of the lamps. This is the wb distant to CP-PACK and they have Conrail style numbers.
Westbound Position Light mast signals at CP-PACK. This is just a basic crossover that was installed with the CTC project to replace DR interlocking a few miles down the line in Derry, PA to provide even 10 mile spacing between crossovers.
Again we see the aluminum relay shacks and yes, its a pneumatic plant.
The westbound signal bridge originally mounted the MP 300 automatic signals. The "SP" (Slide Protection) signs indicate the signals are protecting a slide fence and and trains passing a Restricting indication must proceed prepared to stop short of a rockslide.
3024 automatic, finally a PRR bridge that hasn't been replaced! This is e/b distant to CP-PACK.
Back to color lights at the 3044 automatic. Co-located with the "Hillisde" HDB-DED.
3074 automatic in Derry, PA. This PRR signal bridge would have been part of that DR tower I was talking about. The flat straight track looks like a good place for an interlocking.
The 3102 automatic is a very recent casualty with the PRR signal bridge falling within the last year or two. Still, the new signals were hooked to the old relay logic indicating a problem with the gantry structure. Hmmm, look like NS had to go to Home Depot to get some of those number plates This is distant to CP-TROBE.
Latrobe, PA is home to Arnold Palmer, Mister Rodgers, Rolling Rock Beer and CP-TROBE, seen here. Formerly known as KR interlocking, CP-TROBE is located just west of the Amtrak station. KR used to have an east end that allowed trains on the middle tracks to access the station's side platforms, but since the main line is now only 2 tracks, it's just a single location. The 3rd track is a local branch line joining the main. Here we see a late model PRR gantry supporting three signals, the rightmost only having Medium Speed routes.
At some point since 2006 CP-TROBE lost its pneumatic point machines. Again another silver relay hot housing the D601 control equipment, whatever that is.
Very Health and Safety friendly PRR signal bridge on the west end of the interlocking. The 3rd track has a pot signal for movements entering from this direction.
Far view of the same showing the tk1 signal cleared for another train.
The 3152 automatic and distant to CP-TROBE, more color lights it seems.
The 3184 automatic with that stack train cleared through at CP-TROBE. The right footing of this PRR gantry disappears into the trees.
The 3218 automatic is well known by railfans as it forms the backdrop for photographs from a tall road bridge. It is also a slab steel 70's design that replaced a failed PRR bridge. 15 years later changes in cab design would bring the side mounted mast signal to prominence.
Close shot of the heads with the tk1 signal still at Approach.
Long shot with the signal at Clear...look at that gradient. This location used to be the site of the highly complex SW interlocking (built 1890) that even had a Duckunder track. Today nothing remains. This signal is distant to CP-RADE.
This signal is just short of the Greensburg Station where I caught some local trainspotters hanging out. The two island platforms now only serve what used to be the center tracks.
I am going to wrap things up for now here at Greensburg as my wrists are starting to hurt. The next part will be the finale as we cover the final 30 miles into Pittsburgh.