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. 

Art's LIRR Archives Online...For Now

 Word on the street is that the street is that the person behind Art's LIRR Archives, Art Huneke, has recently passed away. While not quite the #1 source on LIRR tower information, Art's wonderfully Web 1.0 Archive contains a huge amount of primary source material on the evolution of the LIRR in the 19th and early 20th centuries. While the tower and signaling information is scattered throughout the site, it does reward those who take the time to find it. Special attention is given to the older generation of LIRR towers and cabins that were closed in the mid-20th century modernization projects. The page has a wide collection of diagrams and bulletin order scans to track the life and death of these less well known LIRR towers as the rail road evolved into its present form. 

For example Art has extensive coverage of the LIRR's Bay Ridge Branch towers, like NO above, that were opened with the 1928 electrification only to be closed by 1932. In turn we see a photo of the tower that remained open, FN aka FREEMONT, with a Conrail era blue station sign. Other Bay Ridge towers include NU, KN, MJ and of course POND.

At this point there is no word on what will happen to the website so I urge all of you to check it out. Because its all Web 1.0, it is pretty easy to create local copies of the content via the "Save Webpage Complete" function in your browser. Other major signaling content includes:

• B TOWER at Bethpage Jct
• RJ Tower at Rockaway Jct
• R Tower at Richmond Hill
• J/JAY interlocking Construction
• MP/DUNTON Towers 
• WL/LEAD Tower
• BLISS tower
• DB Dutch Kills Draw Cabin 
• PD Tower 
• MV and OLIVET towers
• M Cabin
• D Cabin

Yes, US&S Made Handguns

In the past I have spoken to the importance of looking for the Union Switch and Signal label when purchasing your next M3 switch machine. However, you might also consider looking for the US&S logo when in the market for a M1911A1 .45 caliber handgun. Not only was US&S one of several non-traditional manufacturing concerns drafted into weapons production during World War 2, they were one of the few to affix their corporate trademark to the finished product. Recently Ian at Forgotten Weapons finally got around to covering the US&S M1911 in what might be his only firearm/railfan crossover video

Although they ended up being the second smallest manufacturer of M1911A1 pistols during WW2, this still amounted to over 55,000 units. Anyone familiar with the parts and pieces in a Model 14 interlocking machine can see that making firearms components would be in their wheelhouse. It's unfortunate that Hitatchi has been sidelining the US&S brand after their takeover of the previous parent, Ansaldo. 

Caught on Camera: Track Circuits and Electrification Current

In a previous post covering the phenomena of a "bobbing" track signal that cycles intermittently between one or more states. I mostly covered the spectacle of a particularly egregious example on SEPTA's former Reading Main Line. Here I will cover two additional examples that are a bit more tame, but sheds some light into some operational side effects that come with railroad electrification. 

PATCO FERRY interlocking with an eastbound train on the troublesone WF2 track circuit.

The first example was caught on the PATCO Speedline and involves the cab signal bobbing between 30mph (Approach) to 65 mph (Clear) immediately after a westbound train crossed over to the eastbound track just past the Ferry Avenue interlocking. Was this cased by standing water or a lose wire? Apparently this bobbing signal is a known issue that occurs when the operator or ATO system selects the P4 power setting after exiting the turnout.  The current draw causes the WF2 track circuit relay at West Ferry interlocking to drop.  With the WF2 and NJ67 track circuits both occupied, the signaling system thinks that the train is still on the 30mph switch at West Ferry and drops the cab signal from Clear to Approach.  The train cuts power, the WF2 relay picks up, the signaling system "sees" the train off the 30mph switch and upgrades the cab signal to Clear again.  The process continues until the train passes the next code change point.

As I explained in my post regarding impedance bonds, the rails serve double duty as both a path for traction return current and the track circuit. Because of this a mis-calibrated signaling component can be affected by the acceleration state of nearby trains.    A "safe" failure of this type is less likely to be tested for upon installation or fixed quickly once identifies.  A good example of this is the southern segment of Amtrak's Northeast Corridor that still utilizes relay--based signaling hardware from the early 1980's.

Like with the PATCO example I have been told that the interaction between the signaling system and electrification can be to blame, especially from trains traveling on adjacent tracks. The first example was located at the northbound Milepost 69 intermediate signal near Aberdeen on the less frequently utilized center track #2. The signal can be seen slowly cycling between Clear and Approach, potentially due to an electric train movement on one of the outer "through "tracks". 

Here we see a slightly more extreme example as the southbound Milepost 103 intermediate signal on track #2 at Halethorpe rapidly flickers between Approach and Clear. It might look like Advance Approach is trying to display, but the signal blocks ahead are of usual length and the flicker interval is not uniform. This was noticed after the passage of a southbound Amtrak electric train on track #1. This instance of signal bobbing would also be likely to avoid rapid resolution as track #2 is less frequently used than tracks 1 and 3 and for at least half the day traffic is set in the opposite direction. 

Milepost 103 signal location with track #2 set northbound

Years ago when I had access to Amtrak NEC reports, there would be bobbing signal issues that would persist indefinitely. When the cause is an intermediate side effect of the electric traction system, these problems can become very difficult to troubleshoot as they might require a train running at some specific power load/speed to trigger the problem. A big reason central European countries are so enamoured with axle counters is that many electrified before installing automatic signaling. Counters solve both the problems associated with impedance bonds, but also problems like bobbing signals. 

MARC's Empty ACSES Bracket

In 2020 MARC moved to switch from Amtrak's ACSES transponder based PTC system to the ETMS system used by freight railroads that is more reliant on GPS and data radios. Using two different head units was likely more costly in both equipment and training and dual-equipping rail lines for both ETMA and ACSES has become fashionable over the past decade.  

When I first reported on this move, the ACSES transponder antenna was located in a fairly prominent location behind the fuel tank on MARC's MP36PH-3C locomotives. Since that time the bracket has remained, but the antenna has been stripped off with the cable left dangling.  

I guess MARC is happy with its decision as removing the antenna would make it harder to switch back.

WigWags in Captivity

While the last main line WigWag grade crossing device was removed back in 2021, a few persist on industrial spurs and occasionally on tourist railroads. Most tourist lines have at least one private crossing they can "protect" with a salvaged WigWag, however the method this protection takes can vary and I wanted to show examples of two different ways this plays out.

The first is at the Conway Scenic Railroad in North Conway, NH. There they have paired a pendulum style "[stop] look and listen" wigwag with a manually operated crank style level crossing gate. During operations a railway volunteer is stationed at the crossing to work the manual gate and trigger the Wigwag, much to the delight of the tourists. Of course being a manual operation the crossing protections are non-functional when the crossing is unattended so the wigwag, which was designed as a "magnetic flagman", is not being utilized in a historically accurate manner to replace a flagman.  

The other example involves the Reading and Northern's which has installed a pair of Autoflag #5 "center harp" wigwag signals on  the driveway to the Pittston Regional Transportation Centre. Unlike Conway Scenic, these are activated by track occupancy and will even see activation by freight movements which take place on a more frequent basis than passenger excursions. While they are still unnecessary performance items, the Pittston wigwags still operate in their intended manner even if tourists are not present. 

So although wigwags weren't much of a thing on the old Reading System, I have to give the R&N credit for "importing" some and using them in service. This practice is similar to the R&N obtaining old searchlights and Reading  used bracket masts for their CTC main line.  

Twilight of ATS on the Raton Pass Route

It wasn't long after ETMS PTC systems had been commissioned that the railroads using the older IIATS system went on a tear to decommission the old upside-down canoes. Most notably affected were the CNW-North and Northwest commuter lines operated by METRA, large parts of the ATSF Transcon in Arizona and Missouri and the Amtrak Surfliner route between Fullerton and San Diego. Apart of the NJT RiverLINE, which uses the IIATS shoes as a magnetic trip stop, the last main line use of IIATS is on Amtrak's Southwest Chief route between Albuquerque, NM and La Junta, CO. 

Since BNSF yeeted IIATS off its main lines in 2021, the status of ATS on the Raton Pass route has been somewhat "indeterminate". IIATS had been in service on New Mexico Passenger Rail Authority owned track between Albuquerque and Lamy, NM and as of 2025 the shoes were still in place minus some contraction at the southern end of the territory. Fixed IIATS shoes were also present on the BNSF owned Glorieta Sub to protect specific curves with full ATS territory present on the Raton Sub between Trinidad and La Junta, CO. Imagery shows that the BNSF territory IIATS shoes were also still in place as of 2025.

One might recognize the Raton Pass route as hosting the dwindling number of main line semaphore signals as well as the last main line Wig Wag. That is because the only regular traffic on this stretch of track is Amtrak's daily Sunset passenger train. As a result the route is both PTC exempt and at the absolute bottom of BNSF's priority for capital improvements or even basic maintenance. So while the ATS inductors were still in place it was plausible that the requirement for its operation had been removed along with the rest of the Chief route. Fast forward to 2026 when I noticed this Amtrak delay report for May 12th's westbound Southwest Chief.

3(12) with engines 167 and 14 with 225 customers onboard was delayed departing Chicago Union Station account mechanical was working on loading issues with engine 14. 3 departed Chicago 17 minutes late at 14:42. 3 was further delayed account being stuck in penalty on M1 at CP Roosevelt just outside the station. Mechanical responded to the train, the train maintained HEP. Mechanical initially resolved the issue and the train departed but was soon stopped again in penalty. Mechanical then bad ordered engine 167 and instructed the train to shove back to Union Station. Mechanical responded to the station to replace the ATS shoe on engine 167. The train departed Chicago a 2nd time after an additional 1 hour and 57 minute delay. 

So yes, IIATS is still in service on the Raton Pass route and leading locomotives on Amtrak's Trains 3 and 4 are required to have ATS equipment. A quick check has shown that the new ALC-42 Chargers do not lead on the Chief for this very reason (they were not built with such an old school protection system). Unfortunately Amtrak has filed a petition with the FRA to discontinue the system at least on the BNSF Subdivisions. The reason cited is a lack of 90mph running as opposed to the more typical PTC replacement excuse.

Even when the petition is granted it is unclear if BNSF will bother removing the inductors or clipping wires in the signal cabinets since they don't really get in the way. It is also unclear if the NMPRA (RailRunner) will retire its ATS system at the same time or if that system is even used by anything other than Amtrak trains 3 and 4. 

One final mystery is what happened to the IIATS system on the Raton and La Junta subs in the mid 2000's. In that time speeds on both subdivisions dropped from 90mph to 79mph (the non-ATS equipped national rail speed limit). However all or part of that ATS territory was still in place up to and including the present day (2026). If the track class was downgraded from 5 to 4, it's plausible that use of 79mph instead of 80mph is just a reflexive tic for the BNSF rules department. However I had also been informed that ATS had been "taken out of service" on these line segments despite the fact the timetables had ATS in service. If anyone knows please leave a comment, but if I had to guess BNSF may have started skipping some testing requirement necessary for the speeds greater than 80.