NS Files to Replace Cab Signals with Back Door CBTC

It was no secret that Union Pacific was planning to dismantle Norfolk Southern's significant cab signal territory that was inherited from Conrail after it was absorbed in 1999. While 91% of NS locomotives are cab signal equipped, few if any UP locomotives are after they dropped their own cab signal system around 2022 and a cab signal requirement would hinder creating a nation-wide pool of yellow locomotives. Well it seems that NS has decided to go ahead and file for discontinuance of the legacy Conrail cab signal system notwithstanding the results of the merger decision and what is perhaps even more interesting/alarming is the proposed replacement. 

Unlike CSX or Union Pacific, NS had made significant investments in cab signal territory that lacks fixed wayside signals (what NORAC refers to as Rule 562). While both CSX and UP disposed of their former cab signal territory by just turning it off in favor of existing waysides, UP-NS would have to replacement the wayside capability on hundreds of miles of high density main lines. On CSX's sole Rule 562 route, the former Conrail Boston Line, the solution has been to run trains under Rule 280a "Clear to Next Interlocking" and petition the state for money to restore the wayside block signals. Something similar was my expectation since the UP-NS was announced with UP installing its flavor of wayside block signals from Perryville, MD to Cleveland, OH.

Well, it seems that NS's plan is to implement a PTC based Rule 562 with the PTC system transmitting track authority based on track conditions. While this is pretty much a statement on how ETMS PTC works, the sea change is that everywhere else PTC is still subordinate to good old fashioned wayside signal indications. This removes a sizable chunk of safety and security burden from the system under the concept of "PTC can make you stop, but it can't make you go."  NS's request to the FRA would take ETMS as a safety overlay change it into a bonafide communications based train control system, possibly without any additional modifications. 

Like with CSX, the NS plan would remove the cab signal codes as a source of movement authority which requires the installation of ETMS wayside interfaces at every track circuit block point and hand operated switch. Unlike CSX, wayside signals would only be present at control points with Rule 280a "Clear to Next Interlocking" being the available for various PTC failures. 

The roots of this plan might lay with a trial "Rule 562" system Union Pacific installed on the Hiawatha Sub in Kansas. Since UP discontinued its Automatic Cab Signal system in 2022, the Hiawatha Sub did not gain wayside signals, just PTC antennas at the old Signal Indication Points. Since nothing bad seemed to happen on this low density main line on the prairie, UP might be looking to bring the concept to populated areas regardless of how secure ETMS really is. This might even be the camel's nose for what PTC proponents had envisioned, nationwide moving block signaling.

It's not entirely clear if the FRA will bite, but public comments would certainly help make them aware of the stakes.  Coded track circuits are a secure and reliable way of transmitting movement authority that cannot be easily hacked by AI agents or whatever. Wide area ETMS outages are not uncommon because the system is effectively running on servers in some back office. Of course when these occur its mostly the passenger operations that get canceled because that's where the liability is.  The real shame is that even if the locomotives are no longer responsible for picking up the codes, they will likely exist in the rails transmitting block state for decades to come.

Amtrak Zephyr Trip Report: The More Things Stay The Same

The last time I rode Amtrak's California Zephyr route was in 2017 just after there had been massive re-signaling over the Donner Pass, Utah and the Moffat Tunnel route compared to my previous trip in 2014.  Well 9 years later and surprisingly not much has changed, including the remaining instances of vintage signaling still on the route. 

Starting off with what has changed, UP completed re-signaling efforts over the Donner Pass including the few remaining signals around NORDEN. The SP vintage interlockings around Truckee have also been replaced, However most of the old SP era signal gantries remain standing and along with some of the now turned ABS signal masts on the west slope. Elsewhere on the Capitol Corridor some SP target signals may have been replaced by vertical color lights, but most are still intact. 

The "what stayed the same" list is much longer. First off is DAVIS interlocking which is still equipped with searchlights and a trackside pole line. Relay logic and a US&S unit lever local control power are likely still in the old interlocking tower. Unfortunately I didn't get any photos so here's stuff from 2017. 

In Nevada the SP re-signaled territory west of Winnemucca has been largely unchanged. 

Likewise the classic DRG&W signaling has been largely left in place between Helper and Grand Junction due to the lack of through traffic and the resulting PTC exemption. A few interlockings and ABS signal locations have been replaced and most still featured "turned" replacements, however little replacement progress has been made since 2017. 

BOND interlocking at the junction of the Moffat and  XXXX subs has retained its DRG&W signaling despite being in the PTC zone.  

Also on the approach to Denver Union Station UTAH JCT and FOX JCT are both intact with their original DRGW relay logic and searchlight signals.  

Like everything with signaling, the situation can change without warning so if you are road tripping through any of these areas plan on some side trips to visit these locations.  

Amtrak Electrification Primer

While this blog is dedicated to railroad signaling, I occasionally veer into the command and control of railroad traction power systems because not only does electric power have to be switched and dispatched, but historically it has used much of the same technology used for both railroad telecommunications and railroad signaling. 

Anyway I was recently informed that some documentation regarding Amtrak's present day electric power operation has made it onto the Internet Archive and its definitely worth a read because the documents cover all three of its electrified "zones" (PRR, Hellgate and "Boston") and contain all sorts of easy to read diagrams and photos. It also covers details about the "100hz" signaling power supply including its generation and control which absolutely puts this in the railroad signaling wheelhouse.

How To Be an Amtrak Power Director (2021)

Amtrak Electric Operating Rules and Instructions (2026)

I 'C' You - Caltrain Adopts SP Commuter Plates?

In the bi-polar mess that are Union Pacific Signal rules, an often overlooked feature are the < C > plates that upgrade Advance Approach and Diverging Advance Approach to Advance Approach [Commuter] and Diverging Advance Approach [Commuter]. These modifiers came about in association with the Caltrans funded Capitol Corridor service between Sacramento and San Jose and upgrade the speed restriction associated with an Advance Approach signal indication to 60mph from 40mph.While this falls way short of the 90-110mph operation and 60-80mph high speed turnouts the line should have, its at least a step to improve performance. 

SP vintage mast signals displaying Advance Approach with a < C > Modifier

Anyway, at some point between 2023 and 2024, [ C ] markers appeared on virtually all signals on the Caltrain main line. At first glance it appears that Caltrain was trying to take full advantage out of the performance of its new electric trains  boost the speed of following movements from 50 to 60mph where an unrestricted speed if normally 80mph. 

However a helpful reader left a comment that the new [ C ] plates are simply to mark the signals as displaying Caltrain's speed signaling aspects. In the route signaled area an [ R ] plate is used. I'm not exactly sure which problem Caltrain thinks they are solving, maybe the new MU service involved the hiring of many new operators, but [ C ] and [ R ] are not the best choices for a letter plate. [ C ] for the aforementioned < C > "commuter" tag and [ R ] for the common "permissive" modifier. 

Milepost 25.4 signal before modification. 

Of course there wouldn't be much stopping Caltrain from re-purposing the [ C ] plates to refer to 60mph Advance Approach via a rulebook change if the "speed signal rules" reminder tunes out to be unnecessary.  Just sayin. 

 

NS Re-Signaling Old NKP West of Cleveland

Although far less significant than recent re-signaling in core N&W territory, NS is currently going after routes that were last modernized in the 1980's when the N&W / Southern union was still being figured out. This generation of "NS" signaling was exemplified by Safetran SL-20 modules in a vertical configuration with a simple obround backing, along with mast poles with low cost strap on rungs. Recent photos from 2026 show that a resignaling project is underway on the former NKP main line east of Cleveland. 

Replacements will be of the standard NS type and will add more capabilities for Restricting indications in both a R/Y and R/R/Y form. It is unclear if tubular cantilevers and gantries of 1980's vintage will be retained or replaced. 

Protecting Sharp Curves Before PTC

Located at Milepost 90.3 on the former Rio Grande Moffat Tunnel route is a wonderfully analog system to help prevent inattentive train crews from derailing eastbound trains on an especially sharp 20mph curve. Despite the later deployment of ETMS PTC on the territory this holdover from the days of yore has remained in place and is observable by persons traveling on Amtrak California Zephyr Train 6. 

The Colorado Rockies have a geologic feature known as a mountain "park" which are wide flat valleys surrounded by generically mountainous terrain. The west slope of the DRGW Moffat Tunnel route alternates between impossibly tight canyons with a line speed of 25mph and these wide flat parks with long stretches of 60+ mph running. The mountain park near Kremmling, CO allows for 60+mph speeds between mileposts 82.2 and 86.2 on track that is close to tangent. At milepost 86.6 this abruptly ends in a wheel squealing 20mph curve as the line turns into Byres Canyon.  

To mitigate the risk of an inattentive crew hitting this curve at full speed a radio warning was installed at the milepost 90 automatic signal location. When an eastbound train is detected an audio message about the upcoming 20mph track is broadcast 4 times over the road channel. The distance between the warning and the curve is close to 3 miles and is more than sufficient for the engineer to control the train's speed.

The milepost 90 signal was replaced around 2015 when ETMS PTC was added to the line, however the radio message was left in place and today it serves as reminder of the sort of analog innovation that took place in the analog era like the timer based cab signal drops that were installed at similar high risk locations on the NEC in the 1980's. 

Position Lights Replaced at QUEENS Interlocking

 In 2005 the future looked somewhat bright at QUEENS Interlocking. Although the US&S Model 14 interlocking machine has been taken out of service, the extra long interlocking plant had been rebuilt with brand new PRR style amber position light signals that were set to last 40 years or more. Well changes in LIRR operations that ultimately closed the tower in 2020 have now come for the position lights. LIRR's new "Reduced Aspect Signals" began to appear at the eastern end of QUEENS in 2023 and it was reported that the west end had had its position lights replaced. 

QUEENS East End RAS dwarfs in 2023

QUEENS eastbound PLs on the final day of service.

If there is a silver lining the classic eastbound PRR style signal bridge was retained for the new RAS dwarfs. It is also not entirely clear about what if anything replaced the intermediate PRR PL cantilevers. Or if their conversion is to occur at a later date. 

QUEENS intermediate PL cantilevers in the Winter of 2025/2026.

QUEENS was subjected to numerous re-configurations over the past 20 years as the Main Line 3rd Track project progressed and a new infill station was built at Elmont. When first rebuilt in 2005 QUEENS has 4 PL signal locations dividing the interlocking into 3 logical zones. From west to east this consisted of the original PRR PL gantry, Medium Speed crossovers, modern PL cantilevers, the 80mph high speed crossovers, a modern PL gantry, an unused portion and finally a PL "gantrylever".

Westbound PRR PL "gantrylever" protecting the future 80mph crossover location in 2015.

Original post-2005 configuration of QUEENS high speed turnouts. 

In 2023 the 3rd track project and Elmont station projects added crossovers into the east end, however instead of using the 2005 infrastructure that intended to support this very move, the LIRR depopulated the signal gantries in favor of RAS dwarfs and temporary PRR pedestal signals. 

It was unclear exactly what motivated this change, but the process now appears to be complete. This unfortunately represents a major loss of classic PRR amber position lights on modern 4-track structures.

Reading and Northern's Flexible CTC

From loose car switching to running coal fired steam excursions at main line track speeds, the Reading and Northern has a thing those traditional operating methods that other railroads have shunned out of cost and liability concerns. Based on recent observations this also applies to signaling under degraded conditions, which is a real breath of fresh air compared to public transport agencies that are more comfortable canceling service than working around failure. 

RBMN Pittston train having passed Lehigh Line Signal 148S under normal operation

RBMN Pittston train passing Lehigh Line Signal 148N under normal operation

If you recall my post on Lehigh Line signaling locations, the milepost 148 intermediate signals are located on the former Central RR of NJ part of the line and date from that road's ownership in the 1960's. The signals use a route based approach lighting system where the signals are normally dark unless a route is set in the direction they govern. (Opposing signals remain dark unless the track circuit in front of them is occupied.) The CTC is based on pulse code transmission through the rails and the signal logic also dates from the CNJ era. According to locals the section of CNJ era signaling is not the most reliable.

Signal 148N remaining lit after the passage of the #2102 excursion.

Signal 148N at Approach for UP #4014 following the passage of #2102

The situation I am about to describe was a downstream outcome of a minor derailment of the train used for the Reading and Northern's regular weekend excursion service between Pittston and Mach Chunk through the Lehigh Gorge.  This damaged 3 of the 4 cars regularly used in the consist and because the RBMN was hosting both a Reading #2102 and a Union Pacific #4014 steam excursion the next day, it seemed likely that the "regular" Pittston to Mach Chunk train would be annulled. Sure enough, upon arrival at the Milepost 148 location a route had already been established in the northbound direction for #2102 instead of southbound for the Lehigh Gorge train. Upon passage of said #2102 excursion the 148N signal remained lit and then progressed to Clear for what would be the following UP #4014 movement.  

Single car Pittston to Mach Chunk excursion train passing 148N at Clear for UP #4014

However after about 15 minutes the 148N dropped first to Approach and then to Stop and Proceed. It turned out that even with just a single car available, the Reading and Northern was still going to run the "regular" Lehigh Gorge train. However RBMN management was not too keen on a signaling failure for the "celebrity" #4014 train and instead chose to run against an established CTC route. What I observed was the  gorge train roll past the 148N signal and towards the dark 148S signal at around 20mph. Upon entering the overlap circuit between 148N and 148S, the 148S illuminated to display Stop and Proceed. The Gorge train maintained its speed past the 148S and disappeared out of view around a curve.

#2023 and the single Pittston car approaching 148S at Stop and Proceed against the current of traffic.

Because I didn't have a scanner on me I didn't hear the exact details of what was going on, but there are several valid options. The first would be a permission past the stop signal at CP-CRESTWOOD followed by Restricted speed operation to CP-WHITE HAVEN, likely with additional Form D Line 2 authority. However the even speed of the train around curves and no attempt to stop at the Stop and Proceed intermediate signal implied that the Gorge train was moving under Line 6, "non-signaled DCS rules in effect", with an additional Line 2 movement authority. This method removes the need to stop within half vision and obey intermediate signal indications. 

While this method of degraded mode operation is available to all passenger railroads there is a reluctance to use it during signal failures because the crews have very little experience with moving against the current of traffic and track warrants in general. A few extra minutes delay or bustitution is considered preferable to some sort of accident, which of course makes the "lack of practice" issue even worse. 

Automatic Signals To Be Axed From NY Penn Station Lines 1 and 2

Amtrak is currently halfway through a project to rehabilitate its East River Tunnels that were damaged during Hurricane Sandy way back in 2012. Lines 1 and 2, the southern pair of tunnels between Manhattan and Queens, were subjected to significant salt water intrusion and although this water was removed in short order, the salt created long term reliability problems. The solution has been a three year project to completely gut the tunnels to the 1910 iron rings and then rebuild them with a new concrete liner and a no ballast trackway. As of now the project is half way complete with Line 2 rebuilt and ready for service.  

Unfortunately Amtrak has also taken the opportunity to remove the automatic block wayside signaling within the tunnel. A total of 13 automatic block signals, some dating all the way back to 1910, were removed from the 2.75 mile long Line 2 tunnel. The 5 eastbound and 6 westbound and 2 westbound repeater signals were replaced by Rule 562 cab signaling without fixed wayside signals.  Rule 280a "C" lamps were added to the 708WA and 704W signals in F interlocking along with a new 580E signal at JO interlocking at the western Line 2 tunnel portal replacing the 1E02 automatic. Similar to CP-MID in the North River tunnels between Penn Station and New Jersey, a new controlled point, CP-LOW, was installed 1000 feet east of the 1st Ave shaft for westbound movements. This creates two Rule 280a "super blocks" within the tunnel in case of cab signal failure. 

Existing ABS configuration for Lines 1 and 2 west 

Existing ABS configuration for Lines 1, 2, 3 and 4 east

In a similar fashion to Grand Central and the defunct Cleveland Union Terminal, Penn Station used a unique style of color light signal as the technology of high intensity, long life electric bubs was still relativity new with semaphores being the then state of the art. ABS signals in the East River tubes were of the "frog eye" variety to create an "offset head" appearance that was customary for automatic signals. The upper "head" had the typical R/Y/G lamps with G/Y on the lower. This allowed for a 4 or 5 block progression for trains approaching the slow speed Penn Station complex, Clear -> Approach Medium -> Approach Slow -> Restricting. As signals at Penn Station can only display slow speed indications at best, the two western ABS locations would best display Approach Medium -> Approach Slow. It is unclear how many cab signal blocks have replaced the 5-6 wayside blocks, but CP-LOW's ability to display Cab Speed (60mph) implies that it matches the high density cab signaling installed on the Jersey approaches. 

"Frog Eye' type NY Penn automatic signal pressed into absolute service.

At this point the adjacent Line 1 will be shut down and reconstructed in a similar fashion over the next 18 months. Fortunately Lines 3 and 4, primarily used by the LIRR, were not damaged in the storm and will be left in their original condition for the foreseeable future. As I mentioned before the North River tunnels were already re-signaled in the late 1990's and will be fully rebuilt after the opening of the new Gateway tunnels in the 2030's.

Decoding Transit Signal Labels

 As I have been covering for some time, North American railroad interlocking stations are generally well labeled. However rail transit is quite a different beast and although some systems have adopted railroad practices, the majority have settles on a pair of labeling schemes that at first may look impenetrable, but are actually pretty straightforward. To avoid burying the lead these schemes are:

• Sequential - Interlockings are numbered, often by line.
• Prefix - The interlockings have names, but a prefix is used for observable signage.
• Milepost - The interlockings may have names, but all signals show a generic milepost.

Of the three systems, sequential and prefix are easiest to decode as it is clear what is the interlocking name and what is a signal designation. Milepost is often unhelpful at identifying the real signal number and the real interlocking designation. Even within these broad bins there is aa bit of variation so here are some examples to help with the lesson.

The WMATA DC Metro is one of the more involved sequential systems. Each line segment is given a letter and interlockings are then numbered sequentially from one end of the line to another with any infill interlockings going on top of that.  Above we see the 08 signal of interlocking 03 on the "G" line at Morgan Blvd. 

The MBTA also uses a sequential system for signal markings and formal documents, although human relatable names also seem to exist. Here we see the 1N signal at interlocking #7, aka Park. Both the DC Metro and MBTA have to ensure that a signal number is not mistaken for an interlocking number so in the case of DC the interlocking has a letter prefix while the MBTA uses a directional letter suffix after the signal number.

MATRA also uses a system with somewhat sequential numbers in addition to a line prefix. These are combined with a 3 digit plus alpha signal ID that consists of a track number followed by some sort of two digit configuration or frog type (seems to be 20, 30 or 40) followed by a signal specific letter.  The signal above would be Line "S" (South), interlocking #225, track #2, type 40, signal G.

The second popular system is to use a letter prefix in front of a signal number. The prefix is usually short for a more human relatable name and can usually be decoded by lay observers.  For example the Pittsburgh Light Rail interlocking on the old PRR Panhandle Bridge station is prefixed by FS.

St. Louis Metrolink uses literally signal number prefixes on the same typographic line. This can cause some confusion for visiting observers when prefix like "S" matches a common direction prefix.

Milepost labeling is the least helpful at providing observers with hints as to the proper way to identify interlockings or other railway locations. In this example from the Denver RTD light rail we can see that interlocking signals have the exact same number plate as automatics. This consists of an S prefix for "Signal" a milepost and a line suffix like PR, CC or SW. The lack of information is somewhat mitigated by the provision of switch identification boards which provide both "lever" number and the switch specific letter suffix for paired turnouts.

The San Jose VTA light rail uses a line prefix letter followed by a milepost-y number and then a modifier like A/B or R (for reverse direction).

There are of course many light rail and transit systems all with their own variations or exceptions, like San Diego still using the L/R system found on US&S CTC consoles, but these examples should get the novice most of the way to decoding transit signal labeling. 

Caught on Camera: Clear to Next Interlocking for UP #4014

For much of the Union Pacific Big Boy 2026 Coast to Coast excursion tour, #4014 was able to operate like any other Class 1 main line locomotive with an ETMS PTC box in the cab allowing the engine to operate in the leading position. However the former Pennsylvania Railroad Main Line between Harrisburg and Rochester, Pennsylvania not only remains cab signal equipped, but was converted to operation without wayside intermediate signals in 2018. Until recently Union Pacific was also a major user of continuous cab signals, however in 2022 they chose to scrap their system due to legacy design considerations that created a lack of synergy with ETMS. While it would have certainly been possible to reactivate the cab signals on #4014 and integrate them with ETMS, the increasingly popular solution to run the movement under Rule 280a, Clear to Next Interlocking, was chosen. I was able to catch this procedure at CP-ROCKVILLE on July 7th, 2026.

Here we can see the westbound track 2 signal at CP-ROCKVILLE displaying Slow Approach, R/R/*Y*, with the "C" lamp illuminated for a stop signal at CP-MARY about 5000 feet to the west on track #1. When the dispatcher lines a route between CP-MARY and CP-BANKS, the signal at CP-ROCKVILLE upgrades to R/Y/R Medium Approach with the "C" lamp lit. The plan for #4014 was to proceed past the far end of CP-MARY and then reverse into Enola Yard to spend the night. Note that the Slow Approach and "C" lamps are flashing with the  same cadence. This indicates that the interlocking has a single source for pulsed lamp current that is then directed to the lamps that require it.

LIRR Greenport PTC - Much Ado About Nothing

We have another data point regarding the FRA's PTC paranoia, this time regarding the Long Island Rail Road's Greenport Branch waiver. Although I missed it at the time, in 2021 LIRR Today published a comprehensive article about the LIRR's efforts to get a PTC waiver for the lightly used Greenport Branch (aka North Fork Branch). Previously one of two regularly served lines to still be operating under a form of the PRR's Manual Block System, in late 2017 the LIRR activated CTC and cab signaling over the entire length of the Montauk Branch, leaving the 46-mile long Greenport Branch as the only US commuter rail service running on "dark" main track territory. What followed next was a lengthy pas de deux between the MTA, which really doesn't want to operate the Greenport service and the FRA, which really doesn't want commuter rail services operating under non-signaled (TWC/DCS/Manual Block, etc) rules.

Until fairly recently non-signaled main track operation could be found on Metro-North, the LIRR and METRA. Although the PTC mandate does not require block signaling and CTC, all three quickly caved in and carried out signaling projects (one might also include South Shore which eliminated its APB territory). The only holdout appears to be the Greenport Branch where, for reasons best explained by The LIRR Today, the MTA is highly reluctant to invest capital resources. No matter, although the ACSES PTC system is intended to work with continuous cab signaling, it does not require functional CSS except for following movements between controlled points.

Let's review how ACESS works.

1. Cab signals codes provide movement authority.
2. Fixed beacons between the rails inform trains of permanent speed restrictions.
3. A data radio system informs trains of temporary speed restrictions and track posessions.
4. The data radio can also provide movement authority when cab signal codes are not present.

With these ingredients you can build a dark territory PTC system. ACSES beacons provide the same civil speed enforcement and the data radio provides movement authority between block limits either using the "Clear To Next Interlocking" functionality or by manipulating track possessions (aka 0mph Temporary Speed Restrictions). Remember ACSES does not replace the LIRR Manual Block Rules, it just stops trains if they exceed their movement authority.

 

This is not the solution that was decided upon. The MTA wanted to install the ACSES track speed beacons and keep sing MBS, after all 4 daily round trips are on par with Amtrak's PTC exempt Valley flyer and Downeaster routes. The FRA wanted temporal separation with 1 passenger train on the entire 46 mile branch. Eventually a compromise was reached with 1 train per MBS block with empty buffer blocks between different passenger trains and passenger trans and freight. To be clear the normal mode of Greenport Branch operation is 1 passenger train on the 46 mile  line, but there are edge cases where this would cause problems.

So why did both parties seem to pass on the opportunity to innovate with the technical capabilities of ACSES? A generous answer could be the chance it would have required software changes on the dispatcher's end to give trains dark territory movement authorities as opposed to the dispatcher setting up and releasing possessions. A more cynical take is that the FRA  wants all regularly scheduled commuter/transit services to be operating under automatic block signaling. The deeper issue is that the FRA considers legacy operating methods as unsafe as opposed to PTC being a nice-to-have overlay on an already safe system. The LIRR has safely operated trains under Manual Block rules for decades, just like Metro North and Metra, but apparently they were all jut lucky that tens or hundreds of passengers weren't horribly killed. 🙄 This catastrophizing is what leads to an inflexibility that cancels service, raises costs and pushes more people onto the highways. 

 

BTW, please check out The LIRR Today blog. It has a major discoverability problem on Google so I want to raise some awareness.