A blog devoted to explaining the ins and outs of North American railroad signaling, past, present and future. This blog seeks to preserve through photo documentation the great diversity and technical ingenuity of 20th century signaling and interlocking hardware and technology. Related topics cover interlocking towers and railroad communications infrastructure.
Note, due to a web hosting failure some of the photos and links may be unavailable.
The SEPTA Broad Street Line is notable for being one of the best examples of pneumatically powered signaling appliances in the form of point machines and trip stops. The whole line is equipped with such devices except for the Fern Rock shop and yard complex, which was subjected to a re-signaling project around 2005. Well I just caught word that due to a long term plan to rebuild the City Hall station, SEPTA will be installing bi-directional signaling between the line's WALNUT and FAIRMOUNT interlockings.
Single direction signaling at WALNUT interlocking.
Since it was constructed in the late 1928 it has operated almost entirely with single direction ABS with a few isolated segments of bi-directional signaling within interlocking limits. SEPTA's plans to rebuild City Hall will take entire platforms out of service so the usual practice of closing either the local or express track will not be an option. As a result SEPTA is looking to install some bi-directional capability so the normally 4-track railroad can operate as a two track railroad between Walnut Locust and Girard stations.
It will be interesting to see what brand of signaling equipment SEPTA decides to go with and if they stick with pneumatic trip stops or convert to electric. After the MFL was re-signaled around 2000, SEPTA was able to bank a large amount of 1980's vintage pneumatic trips and A-10 point machines that have been slowly appearing on the BSL so there might be enough in stock to supply the project. Since the wayside signal system is likely to be replaced around when new rolling stock is purchased, this would save money on an ultimately short term change. On the other hand if someone else is paying, SEPTA could decide to rid themselves of a "troublesome" technology. There could also be a mix with the existing equipment left alone and only the new reverse direction signals getting electric. Regardless, I think I might take the time to get photos of whatever is currently in place.
On November 6th, 1984 the last train departed the historic Reading Terminal in center city Philadelphia 4 days after the completion of the Center City Commuter Connection tunnel that allowed through running between the former Pennsylvania and Reading electrified commuter rail systems. Immediately after crews began to rip up the tracks as the tunnel had rendered both Reading Terminal and about 2 miles of elevated main line redundant. This also marked the end of RACE STREET as an active interlocking station and its task of signaling trains in and out of the 13 track station complex from the 4-track Reading Viaduct. Built in 1930 in conjunction of the Reading's own suburban electrification project to replace the previous interlocking from the 1890's, RACE STREET, or "RA" as it was known in the days of the telegraph, would fall to the wreckers ball as the viaduct between Arch and Vine streets was turned into a mix of event space and parking to support the new Pennsylvania Convention Center, that would also employ the Terminal train shed as an event space.
The surprisingly modern RACE STREET ("RA") tower at left.
While the demise of a historic terminal interlocking tower is nothing new, even finding a photos of RACE STREET was devilishly hard due to its position two blocks from the end of the passenger platforms and often located behind stored MU equipment. At 111 levers, RACE STREET's US&S Model 14 machine was as
large as the one in HARRIS, but it features only 68 working levers, the same
amount as the total number of levers in CORK. In addition to fanning 4
main line tracks into 13 station tracks, it also featured a junction
with the single (originally three)
track "City Branch" freight line and two storage pockets on the tower
side of the terminal throat. The interlocking consisted of roughly 4
parts, each delineated complimentary signals. From north to south this
was the outer set of medium speed crossovers, then the City Branch
junction with a 3x4 double-slip field, the trailing point double slip
ladder and then the final terminal fan. The terminal area made liberal
use of Restricted speed routes with no signaled routes in the fan and
only a select few in the trailing ladder. Of course this is all mostly
academic as everything south of the City Branch junction was demolished
What about north of the junction?
Despite the demolition of both the tower and the core of its
interlocking plant, significant artifacts of race street remain in
roughly the condition they were left in 1984. This is because the main line viaduct north of Vine Street
was abandoned in place as an electric power right of way to reach a
rail power substation. While much of the track structure was removed,
the overhead lines and their supporting gantries were needed to feed the
electric power and attached to those gantries were RACE STREET's 1930
vintage color light signals. In 2012 the substation was replaced, ending
active use of the viaduct for rail purposes, and the viaduct became an
urban exploration hot spot with plans to eventually convert it into a
High Line style linear park.
Working northward, the first surviving signal bridge is on the curve immediately adjacent to the Callowhill 25hz railroad power substation and features northbound high signals 20L and 18L for tracks 4 and 2, in addition to southbound high signals 28R and 26R for tracks 1 and 3.
The southbound 28R and 26R signals featured a full upper head, a middle head with green and red lamps and a Reading style horizontal head with the yellow Restricting lamp. The reason for the middle Green lamp without an accompanying yellow is somewhat unclear but I suspect that R/Y/R Medium Approach was unavailable in favor of R/R/Y Restricting. The only non-restricting signal south of here is on track #2 so both Approach Medium and Medium Clear would be possible.
For northbound trains the 18L and 20L signals are protecting medium speed main line crossovers. Track 4 had no diverging routed and was only supplied with a R/*/Y below the 20L full speed head while the 18L had two regular medium speed routes over the #17 and #15 switches.
Both the 18L and 20: also feature metal ID tags on the back of the upper signal head. I'll also point out that all of the color light signal hardware is US&S style TR target (tri-light) with unitized lamp housings.
The next surviving gantry hosts the southbound 16R and 14R track 2 and 4 home signals and the southbound automatic track 3 and 1 exit signals.
The 16R and 14R are mirrors of 20L and 18L except in this case the local track gets the diverging route over the #13 switch.
The automatic exit signals are also nothing special, although the numbering system is a bit hard to figure out and apply to further automatic that are not on the diagram. It is also important to point out that tracks 1, 2 and 4 were bi-directional with the 16L signal able to display Slow Clear for straight movements, while the 14L on track #3 could only display Restricting.
A mere 800 feet down the line was the first automatic signal location with three northbound signals on tracks 1, 2 and 4, and southbound signals on all 4 tracks. The reason for the asymmetrical signaling was due to the presence of the Reading's MU storage yards on the east side of the line at North Broad. Deadhead moves heading to and from the yard would use track #4 in the shoulder peak.
Typically when one discusses a signal cutover one is cutting new signal logic over to control new or existing signals or interlocking appliances. Sometimes one will cut new signals or interlocking appliances into existing signal logic. However in 2014 when SEPTA wanted to relocate 90TH ST JCT SOUTH interlocking 2000 feet to the north to expand a Conrail SAO industrial siding they took things a step further and relocated the entire signaling bungalow.
Above is a street view of the original location in 2014. Below is the new location in 2015. SEPTA didn't even bother to clean the graffiti off the relay hut.
Part of the penny pinching shown here is due to 90TH ST JCT SOUTH being solely the domain of Conrail freight movements before they hit the SEPTA Airport Line at 90TH ST JCT NORTH. Without a Federal or State grant to pay for the capital improvement, there was no incentive to pad things out and create more jobs and with traffic being pretty minimal there wasn't a cost incentive to minimize down time due to testing. This just goes to show when the costs align, railroads will save money on signaling.
While trying to gather information for my recent SEPTA Unilens post, I discovered a newish railfan video channel with a large amount of up to date of front facing video content that can help with signaling research. Retired Railfan Horn Guy has been crisscrossing the country shooting a mix of front window and standard videos with special emphasis on SEPTA and, more recently, Caltrain. The latter is particularly useful given the impending demise of forward facing views on that line.
The guy is based on Long Island so naturally there is LIRR content, but he doesn't seem to have the same level of access as some of the other LIRR specific video channels that I suspect have insider access. Anyway, its a fantastic channel and good resource to bookmark.
In yet another chapter of the rail industry's love-hate relationship with the Safetran Unilens signal, over the last few years SEPTA has been systemically replacing its Unilens signals with L&W LED searchlights similar to those being employed by Amtrak in the Chicago, New Orleans and Albany terminal areas. Although I am in the Philly area and perform various SEPTA excursions I only just noticed the change since they were limited to the former Reading Company lines I haven't ridden lately. Below is an example of a compact Unilens "high" mast at JENKIN interlocking since 2006 that was converted from Unilens to LED searchlight at some point over the last 2 years.
Track 2 LED searchlight high dwarf at JENKIN in 2003
Track 2 LED searchlight high dwarf at JENKIN in 2010
Combing through some SEPTA territory railfan window videos I can confirm that the majority of Unilens signals have now been replaced by LED searchlights. including those at NEWTOWN JCT, TABOR JCT, the Fox Chase sidings and Norristown Elm St. Because of SEPTA's use of reduced aspect signals, new searchlights won't get much opportunity to demonstrate their full rage of colors and the clipped flashing might be a little irritating while displaying "cab speed" indications.
LED Searchlights at Albany Union Station
For those of you who might be encountering the Unilens saga for the first time, the Unilens was created as a solid state replacement for the traditional electro-mechanical searchlight. It makes use of plastic light pipes (think big fiber optics) to deliver light from up to 4 lamps to a single lens assembly. While this might sound like a great solution, apparently the product suffers from expensive propritary incandescent bulbs and degradation of the light pipe that reduces output over time as well as giving green indications a yellow cast. While some of SEPTA's Unilens dwarfs were approaching 20 years in service, some, like those at Norristown, had been installed less than 10 years ago. It's entirely possible that the long term costs of operating the type became just too much. It will be interesting to see if LED searchlight technology migrates to the Class 1's, which still seem wedded to the Unilens for restricted clearance applications.
The primary goal of the project was the allow select trains to turn back at the University City station, instead of 30th St, which required the addition of crossovers and a tail track between the old limits of ARSENAL and WALNUT interlockings. However SEPTA used the funding opportunity to renew the 12kv overhead lines and 1980's vintage ARSENAL interlocking, which unfortunately saw the demise of amber type PRR position lights, some of which were 2000's era LED upgrades.
An extension of ARSENAL southward to include a new trailing point crossover on the West Chester Line resulted in the old northbound signal bridge now serving only the NEC bound tracks. Note that the signal from the NEC can display full indications instead of SEPTA's go-no-go 562 indications.
In the other direction two new automatic exit signals have been furnished as distants to PHIL interlocking. With Approach Medium/Limited being the most favorable indication this could be seen as a downgrade for Airport Line routings that should take place over a Clear signal, however the ACSES speed enforcement doesn't make 45mph possible, let alone the actual line speed, so no big loss..
ARSENAL's southbound limits have been relocated about 900 feet to the south. This will substantially reduce transit time through the interlocking so that an NEC train can follow more closely behind a West Chester Line train .
The big surprise was the complete removal of the WALNUT crossovers in the trench leading up the tunnel approaching 30th St Station. Possibly due to maintenance issues involving water drainage or foul time associated with close clearances, the lack of WALNUT's crossover will risk snarling service if there is ever a need to single track/wrong rail through 30th St Station. Southbound wrong-railing trains at 30th St will have to travel 1.5 miles to ARSENAL whole northbound trains can benefit from the new turnback crossover for a 1.1 mile penalty. I'm not a daily rider, but hopefully I'll have a chance to pick up on how the new configuration help or hurts the user experience (as opposed to the bottom line).
Unlike previous generations of automatic train control, the on board PTC software has as much if not more to do with the operational impact of the safety system than fixed infrastructure like code rates and block length. In the case of ACSES, Amtrak's PTC implementation, track mounted transponders conveys data about upcoming civil speed limits, grades and positive stop points and it is up to the on board system to develop a braking curve. In theory this curve should represent the maximum braking effort the rail vehicle is capable of if tripped by the PTC system to prevent an unsafe level of overspeed. The concept of a penalty brake application exists for thus purpose as a full on emergency application requires some additional inspections. (Although I have been present when the "freight" ETMS PTC system threw my Amtrak train into emergency.)
Four years ago I benefited from a SEPTA training run to capture two videos of how their PTC implementation functions and the braking curve was ridiculously bad. Granted I lack similar curve information for other operators, but the SEPTA engineer could stay under the curve with a very mild brake application. I got some comments on the order of "PTC is new and SEPTA will inevitably made modifications to improve the performance." Well on my most recent winter SEPTA fan trip I lucked into another training run on the Airport Line and I can report that the system has not been changed and it still causing significant delays.
Unfortunately I was only able to capture video of the cab display unit returning from the Airport to Eastwick which had no PTC speed downgrades and therefore no demonstration of the braking curve (although I did capture a missed transponder reading). In fact my inability to get a video angle was doubly unfortunate because the braking curve is so conservative that it caused the engineer to trigger a penalty brake application just north of PHIL interlocking's southbound home signal. This is where the line speed of 45mph transitions to 30mph for the Airport Line curve just south of PHIL interlocking. (Even before ACSES this curve was protected by a 45mph Approach Medium cab signal) This meant that the on board system calculated a braking distance of about 4500 feet to slow from 45mph to 30mph.
Time for some math. The starting velocity is 66 fps and final velocity is 44fps. From my observations the braking "curve" is linear which gives us an average speed of 55fps and thus a deceleration time of 81 seconds. This lets us solve for acceleration with a solution of 1.38fps^2 or 0.9 mphps, which is an absolutely pathetic braking rate. Even if I assume I was wrong about where the speed curve kicked in and the penalty took place just after the limits of PHIL interlocking, 2800 feet from the restriction, the resulting deceleration rate is still 1.4 mphps, less than half of the design acceleration rate of 3 mphps.
In this example we have the two bugaboos of PTC working together to sap performance on what should be a speedy trip to the airport. The first is a stacked safety margin. The older ATC system enforced a 45mph limit on approach to and around the 30mph curve. That would have been a rough ride and close to the overturn speed, but would likely be enough to prevent a derailment without getting in the way of the engineer. Today the ACSES takes the 30mph as gospel even though that figure already accounts for human error. Next, the conservative braking curve compels a speed reduction about three times farther away than would be necessary with the full braking force available. The end result is net gain of 10 seconds to traverse the same 4500 foot distance and you can see why this is a problem. 10 seconds isn't much. It's certainly not enough for anyone to fight for or risk being blamed for if something goes wrong. unfortunately this 10 second loss happens again and again and again over the course of a run with the end result of SEPTA having to lengthen scheduled running times by an average of 4 minutes across all of its lines. Add in more small delays like low maximum speeds, long dwell times, slow terminal operations and voila, rail transport is uncompetitive with private road transport.
As you can see in the above video SEPTA cares very little about speed in general. As seen in the video about, the R1's 4-station airport terminal complex has blanked Restricted speed limit, even when approaching CP-AIRPORT JCT after passing a wayside automatic distant displaying Approach Limited. Why even bother with the wayside at that point! Prior to ACSES, SEPTA had plans to use the 4-speed cab signaling system to implement rapid transit style signaling when Rule 562 operation was installed on its Reading territory. Maybe we'll see a realization similar to NYCTA's that speed improvements, even small ones do matter. Or maybe we'll see the response to poor post-COVID ridership to be service cuts.
Light rail is currently the locus of signaling innovation in North America due to its mix of limited regulation, low budgets and legacy systems. For example I have previously written about DART's three differentsignaling methods in use on its light rail network. In Philadelphia, one such legacy system is the suburban trolley lines running out of 69th Street terminal on the western Philadelphia border. Similar to Pittsburgh's south hills light rail lines in concept, the method of operation is currently being converted from a basic trolley era ABS system, to a hybrid CBTC system. As I just managed to pick up a bunch of new photos, I figured it was a good time to cover both systems while they are still in the transition period.
Route 101/102 block signals at 69th St
The ABS system inherited by and later updated by SEPTA as necessary, was a 2-block affair with signals displaying proceed (green) or stop (red). Although there was one location, Drexel Hill Jct, that could be described as an interlocking with full signal protection and a power operated facing point switch, the entirety of the Routes 101 (Media) and 102 (Sharon Hill) were run under traditional ABS rules with hand throw crossovers and spring switches entering sections of single track.
Two aspect ABS signals at a Route 101 hand throw crossover including operator hut.
The single track segments were handled with an automatic tumbledown scheme and the one junction was fitted with a three lamp signal and a route selection punch box. Where a diverging move was encountered a yellow signal indication would be displayed. There was also no ATS or ATC enforcement of signals or speeds.
Legacy yellow diverging aspect at east end of Route 101 single track segment.
Due to the sections of street running and close spacing of stops, the Suburban trolley LRV's are considered to have sufficient braking performance to dispense with an Approach type indication. Signals are approached prepared to stop and when the next block is cleared, the following movement will get a clear signal to proceed. Not all of the route miles are protected by signal indication with the street running and other slow areas working on sight. These sections are partly defined by "end of block" signs.
Route 102 switch protection signal paired with a single track block entrance signal.
In addition to the two lamp ABS signals, there are/were switch position indicators and reverse direction protection for the single track sections and Drexel Hill Jct. When entering single track and exit signal would follow the spring switch to protect against a race condition if two opposing trolleys were to attempt to "seize" the single block at the same time.
Route 101 single track switch signal with block entrance signal in distance.
Starting in 2019 work started on a new CBTC based signal system that would also make use of sizable number of interlockings to replace hand throw crossovers and single track spring switches. As of early 2022 the CBTC system had not yet entered service so the interlockings were used to supplement the existing ABS signal system.
New SEPTA Suburban Trolley cab display unit with CBTC disengaged.
In fact on the combined section between 69th St and Drexel Hill Jct there were sufficient interlocked crossovers to supplant all of the ABS signal locations! As many of the ABS block signals have so far remained on the routes past Drexel Hill Jct during the transition period, it is anticipated that the CBTC will provide full block separation, not just a safety overlay.
New Route 101/102 combined trunk interlocked crossover and block section signal.
All in all the project involved the addition of 10(!) new interlockings, three crossovers on the combined Rt 101/102 trunk, Drexel Hill Jct, one crossover on each Rt 101/102 branch, three Route 101 single track endpoints and one Route 102 single track endpoint. In addition to these interlockings, three additional holdout signal locations were installed in proximity to an interlocking.
New interlocked holdout signal at entrance to Rt 101 single track territory to accommodate short turns
Another interesting new feature is the provision of a yellow fixed ATS transponder adjacent to each fixed absolute signal.
Yellow ATS transponder located between mast base and rail.
Although I was unable to observe every detail of the current operation it appeared that the new wayside interlocking signals were backwards compatible with the old ABS system displaying R - Stop, G - Clear, Y -Diverge. The presence of a 4th lamp hints at at the presence of a lunar white indication that will either be used for a "cab speed" (most likely) or an absolute block / restricting signal.
Same location as above prior to rebuild with spring switch and yellow "end of block" sign indicating start of line of sight operations.
Although the new CBTC/CTC system is modern and high tech, it never the less exhibits the limits of technology to deliver substantive performance gains. Ten new interlockings along with 20 or so miles of CBTC will cost more to maintain than the legacy ABS system. Furthermore, the speed control function will almost certainly decrease performance from current standards. On the other hand contingency operations will be greatly improved with track work becoming possible during operating hours and vehicle/overhead line failures now able to be worked around without the need for temporary block operators hand throwing switches. In theory the capacity of the system will improve, especially on the route 101/102 combined trunk, however the decision to run more frequent service has always been limited by the budgets and political will of both SEPTA and various levels of government. My assessment is that operations will say the same, liability will decrease along with speed and the impact/cost of contingency operations will decrease enough to offset the high cost of the new signaling system, at least until the point that the technology becomes unreliable.
Well, once again I put my hand up to do a program for an NRHS Chapter meeting and since it was for Philly Chapter instead of West Jersey I was able to partly re-cycle my 2008 presentation on Pennsylvania Railroad Interlocking towers on Amtrak's Harrisburg Line. Of course back in 2008 ZOO, OVERBROOK, PAOLI, THORN, PARK, LEAMAN, CORK and STATE was not only open, but relatively intact. Fast forward 14 years and only THORN, PAOLI, OVERBROOK and ZOO remain with the first two clearly on their way out.
My plan was to refresh the presentation with the updates and refreshed photographic content (including from my 2019 THORN visit). The reality was that the quality of my 2008-edited photos was woefully inadequate and it took me a good 5 hours to get everything up to snuff. To avoid any awkward dead air I preformed a two hour practice session on my live stream and that is what I am now able to present to you. There are a few hiccups here and there, but overall I am happy with the result.
Ironically the live chapter presentation had to be split into two parts because a number of Philly chapter members take SEPTA to the meetings which limits the duration to an hour. 🙄
This post had been planned as an update on SEPTA Signaling encountered during my SEPTA Mid-Winter fan trip, but after a couple of additional rail adventures in the December/January time period I figured I should address them in a single post.
The headline news item is that the SEPTA West Chester Line has been converted to Rule 562 operation with cab signals and no intermediate wayside signals. This is surprising as the line had already been converted to Rule 261 with cab signaling and it appears that SEPTA had to go to the trouble of removing the wayside masts, exposing themselves to all of the attendant issues with cab signal failures. The most significant loss are the distant signals that had been fitted with Reading style two lamp lozenge heads, that have not really been fitted anywhere since.
One the other hand, no changes were made to the interlockings CANE, MEDIA and NORTH/SOUTH ELWYN. They still display full indication and not just Cab Speed and Restricting. Also ARSENAL interlocking is still hanging in there with the LED position lights on the north end and full range color lights on the south end.
On the Routes 101 and 102 Suburban trolley, the long metastasizing CBTC project may or may not be in operation. What has changed is that SEPTA has added a large number of interlocked crossovers and also interlocked the ends of single track operation. This actually seems to have increased the number of wayside signals. In addition to this, the old two aspect ABS signal locations appear to be in place, making me wonder if the CBTC is not yet active or if it will be a safety overlay like in the tunnels with no increase in capacity.
On the Route 100, the passenger stop request signals at stations are still in place, but the short stretch of 3rd rail used to cancel them are now being removed.
On the Amtrak Harrisburg Line / PRR Main Line, the crossovers between #1 and #2 track at OVERBROOK interlocking (levers 13 and 15) have been converted from pneumatic to electric operation. Not sure what the plans or timeline are, but I figured that OVERBROOK would be replaced and removed, not closed, so this actually might represent a live extension.
Moving out along the PRR Main Line, the legacy signal bridges at Cove and CP-BANKS have been removed having been out of service since 2018.
Finally, no work appears to have been started on the off again, on again, NS D&H Main Line re-signaling project between Sunbury and Binghampton. I visited a number of locations including CP-DUPONT and there is absolutely no evidence of prep work. Hopefully that continues to limbo along for many years.
NORTH PHILADELPHIA is an interlocking emblematic of Philadelphia's industrial strength and the Pennsylvania Railroad's wealth and technical leadership. NORTH PHILADELPHIA is an interlocking emblematic of Philadelphia's industrial decline and Amtrak's chronic lack of funds. NORTH PHILADELPHIA is not an interlocking, and is barely a station. All of these statements were at one point true and thus track the up and down fortunes of the PRR's third great tower in the Philadelphia terminal area. Constructed in 1914 on the Connecting Railway that linked the PRR's East-West Main Line at Zoo Junction to the Philadelphia and Trenton railroad at Frankford Jct, NORTH PHILADELPHIA was a direct sibling to FAIR tower in Trenton and similar in style to UNION JCT and B&P JCT towers in Baltimore and was built to control the important North Philadelphia station complex along with the junction with the lucrative Chestnut Hill suburban branch. In this the first part of a two part series we will look at the layout and history of NORTH PHILADELPHIA interlocking before moving inside the tower in part 2.
As built in 1914, the North Philadelphia interlocking complex comprised a laundry list of "thoroughly modern" and "high tech" transportation concepts. The station featured 12-car 48" high level platforms designed to seamless transfer for passengers on long distance through trains to access downtown Philadelphia without those premier trains needing to make a costly stop at the stub end Broad Street Station. All of this was controlled by a 47-lever Union Switch and Signal Model F all-electric interlocking machine with a lighted diagram and multiple clockwork rundown timers to prevent delays. The entire 1915 rebuild project also coincided with the suburban electrification project that would bring 11kv 25hz overhead wires to Chestnut Hill.
The interlocking consisted of a trailing point ladder on the east end and a facing point ladder on the west end that doubled as a two-track into six-track flat junction for Chestnut Hill suburban trains. Between these two ladders were crossovers that allowed access to the additional station platform tracks. The tracks were arranged such that through freight trains would use center main tracks 2 and 3 unencumbered by the high level platforms, the outer passenger tracks 1 and 4 would split in to at each high level island allowing express trains to pass platformed locals and a pair of yard tracks, 0 and 5, running on each edge of the right of way to service local industry. Lever numbers ran from east to west and the facing point ladder on the west also featured a pair of double slip switches across tracks 2 and 3 as well as a diamond where the #5 freight track crossed the outbound Chestnut Hill track. Due to a tight curve on the Chestnut Hill suburban tracks, slow speed (15mph) routes for those movements was seen as acceptable.
Main Line electrification to Trenton arrived in 1930 and with it North Philadelphia saw a number of significant upgrades. Chief among these was the application of Pennsylvania Railroad position light signaling and with it the iconic 10-track signal bridge at the western end of the island platforms (although due to the use of single direction signaling only four signals were actually mounted on said gantry) along with older style dwarfs.
Switches were changed from electric to pneumatic operation and two additional crossovers were added (using spare levers #1 and #2) at the eastern end of the platforms to allow trains their choice of center or edge tracks as express passenger trains made increasing use of the center "freight" tracks. On the interlocking machine electric switch amp-meters were removed and additional rundown timers were added since this era of interlocking did not support zoned timers. On the Chestnut Hill branch a trailing point crossover was added just north of the platforms protected by a pair of signals on each track. Without room on the large Type F frame, the new crossover was accommodated on an adjacent 4-lever US&S table interlocker. Finally, some #20 (45mph) turnouts were added, but no Limited speed routes were provided for.
The post war period could likely be considered peak North Philadelphia as in the following decades industrial retreat combined with white flight turned a vibrant middle and working class community into a marquee example of urban decay on par with the Bronx and South Central. Not only did the East-West long distance trains that made North Philadelphia a vital transfer point evaporate, but the local ridership also plummeted due to the aforementioned neighborhood collapse. The freight services were also in disarray with the Penn Central imploding into Conrail and Amtrak taking charge of the Northeast Corridor route that was still configured in the manner of the combined passenger-freight operations of the PRR era. With funding from Regan's Washington in short supply the 1992 edition of NORTH PHILADELPHIA looked surprisingly like the 1972 version with only the #1, #2 and #29 station track access switches removed and the two double slips re-aligned into coventional turnouts.
Regardless it was hard to deny that NORTH PHILADELPHIA was over-built and many of the freight tracks and sidings were falling into weedy decay.
The early 1990's would see a huge push by Conrail and Amtrak to disentangle their operations on the former PRR. Via a new connection at the Reading's old Park Jct, the Conrail Trenton Line would take the place of the old #5 track through NORTH PHILADELPHIA interlocking with the deletion of the #45 and #5 switches and associated signals. Around 2000 Amtrak finally scrapped together enough funding to begin their NORTH PHILADELPHIA modernization effort.
The over the course of a couple years the entire east end of the interlocking save for the #11 and #17
crossovers was removed and reestablished as a new interlocking named
CLEARFIELD, remote to the CTEC dispatching office effective 2003.
Moreover the antiquated station track system was remedied via a wholesale track re-alignment with "Eastward Station" being through routed as Track #1, Track #2 being cut between the #47 and #17 switches, and a new Track #2 being routed along the eastbound platform. This left a rusting portion of concrete tied NEC track on the old track #2 alignment for a number of years after.
Former track #2, removed and relocated.
Finally both the Westbound Station and 0 tracks north of the westbound platform were removed at the 32R and 34R signals.
At this point NORTH PHILADELPHIA entered its most awkward phase of existence as a black hole on the dispatch board generally only able to participate in moving R8 SEPTA trains on and off the Chestnut Hill West line and trying not to delay through trains on the NEC. Perhaps the most inconvenient part from an operations point of view was NORTH PHILADELPHIA's continued configuration for single direction Rule 251 ABS operation when the NEC on either side of it had long since been upgraded to bi-directional CTC. Trains arriving on wrong-direction tracks would need to take a slow speed indication from a dwarf signal and stay at 15mph through most of the long interlocking.
Eastbound 40L and 42L home signals.
As 2005 approached Amtrak began to make the final push towards eliminating NORTH PHILADELPHIA. The pneumatic point machines were replaced by electrics, new high position light signals appeared on the westbound super-gantry and a brand new eastbound signal gantry was erected.
The track layout was predictably simplified with the 31 and 33 switches being removed along with the associated diamond and north side stub tracks. The #25 crossover was also removed limiting westbound parallel Chestnut movements to track #4. On the main ladder all the crossovers were aligned for Medium Speed (30mph) operation and the new signals were able to reflect this.
Finally the trailing crossover on the Chestnut Hill branch itself was removed shifting the division point with SEPTA to the 10-track signal bridge. However the former 50L and 52R signals remained for another decade as automatics.
Former NORTH PHILADELPHIA 50L turned automatic signal 50CH
In the summer of 2005 NORTH PHILADELPHIA tower was closed after 91 years in service with the new Chestnut Hill Branch junction being named LEHIGH after the nearby street. It's single facing point ladder complimenting the trailing point ladder at SHORE interlocking 2.6 miles to the east.
