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.
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| Amtrak CLEARFIELD interlocking crossovers looking westbound. |
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.
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| 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.
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| 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.
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| 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.
With this context in mind, join me next time as we head into NORTH PHILADELPHIA tower before its closure for a look at the interlocking machine and related equipment.
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