Amtrak THORN Tower to Close Aug 8, 2026

For over a year I have been tracking the slow motion closure of Amtrak's THORN interlocking tower. located on the old PRR Main Line in Thorndale, PA Opened in 1938 as part of the PRR's electrification project to Harrisburg, THORN was equipped with a state of the art CTC unit lever console controlling  4 remote interlockings in addition to the local 6(!) track full crossover. THORN's extended territory, including FRAZER interlocking which was commissioned in 1994, is what has allowed for the prolonged multi-year closure, which will take place just shy of the tower's 90th year in continuous operation.

Since the first part of THORN's territory, CALN interlocking, was chipped away back in 2020, the local 6-track crossover was rationalized and then turned over to CTEC control while the THORN operator continued to handle SEPTA movements in and out of Frazer yard as well as the daily NS freight entering the line at GLEN. More recently DOWNS interlocking was prepared for complete removal, its signals left standing as the change point between CTEC and THORN's control.  In the final act, kicking off in early 2026, GLEN and FRAZER interlockings were reconstructed with the goal of a Rule 562 cutover once all of the work had been completed. 

THORN interlocking as rationalized in 2023

The closure will bring full bi-directional operation between THORN and PAOLI, with the segment between FRAZER and PAOLI remaining outside the Rule 562 zone for now. The much diminished PAOLI tower is likely next on the list for closure before the heavy lift of installing Rule 562 on the core of the old 4-track "Main Line" begins. One loss that's easy to overlook is the now vestigial limited speed triangle at DOWNS interlocking with those at BRYN MAWR likely the only set remaining outside of Canada.

Another loss will be the intermediate signals at Exton, which were easily accessible from the SEPTA parking lot and well positioned for photography. 

For persons desiring photos of these, the Milepost 29 signals or what's left of DOWNS, you probably have until August 7th assuming transition operations will take place overnight. At 1:30pm on August 8th, THORN's final staffed shift will end. The tower is directly adjacent to the Happy Day's Diner for anyone looking to mark the event.