Amtrak's Secaucus High Density Cab Signaling in Action

When the Secaucus transfer was being designed and built around the year 2000, Amtrak implemented a new "High Density Cab Signaling" concept with shorter blocks and additional cab signal codes in order to increase the capacity of the approach into Penn Station especially with all the NJT Corridor and Midtown Direct trains stopping at Secaucus. This would replace the PRR era Rule 261 signaling with mile long blocks. Below we see the 2E signal at ERIE interlocking cycle through its indications after an eastbound NJT push-pull takes a Clear signal upon departing the track 2 station platform. 2E was fleeted for a normal route and immediately went to Stop and Proceed, then Slow Approach, Approach, Approach Limited and  finally Cab Speed (which could represent both 60 and 80mph speed codes). The horn at the end was an approaching Amtrak Regional which ultimately took 2E at Clear (not captured on video).

Unfortunately this was just in time for NJT to lean into Push-Pull service which lacked the acceleration to and braking systems to take advantage of the rapidly changing speed codes. On push-pull sets with traditional air brakes, crews would often target one speed below the one being displayed to avoid jerky train handling and the risk of penalty brake applications in the face of frequent cab signal drops.This negated much of the intended speed benefits from the high density cab signals. For whatever reason, similar High Density Cab Signals could be found on the 2005 era western Harrisburg Line re-signaling, however due to the low traffic density, Amtrak has taken to disabling some of these extra code change points.

LINCOLN Lefty: Story of the PRR's Left Handed Dwarfs

 Anyone looking at the NORAC signal aspect charts may have noticed that the familiar PRR dwarf position lights have a curve to them (or yaw) that can go both ways. For all four dwarf indications, Slow Clear, Slow Approach, Restricting and Stop, one will see two entries on the diagram chart, one with a left hand curve and one with a right hand curve. To the uninitiated this can be dismissed as having to do with clearances or which side of the track a dwarf signal is placed, but it actually represents a fairly early change by the PRR to make a more practical signal vs a more conceptually accurate signal. 

The first PRR position light signals were designed as a replacement for semaphores. Version 1 or "tombstone" position lights (due to the shape of the backing) consisted of 4-lamp lines with an off-center pivot point that directly mirrored the shape and function of a semaphore blade. The position light dwarf signal was no different, but used two lamps to mimic the right to left sweep of a dwarf semaphore. Originally only three positions were provided, stop, low speed prepared to stop and low speed, again matching the function of the dwarf semaphore. 

Between 1918 and 1925 the three lamp system with circular mounting became standard for high signals, but the dwarfs, unable to be simplified further, retained the design aesthetic of a semaphore blade sweeping out a curve. The one major change was that someone noticed that the 4-lamp PL dwarf could display the reverse \ for free and a distinction between "proceed expecting stop" and "proceed expecting obstruction" was able to be made. The result was the left-handed dwarf position light.

Made of cast iron by Union Switch and Signal, the left hand dwarf had bulb access hatches on both the straight and curved sides. The rest was a sealed unit with a small vent on the back. 
 

This model of PL dwarf would go on to be installed at all the great PRR signaling achievements of the 1930's such as ZOO and HARRIS, however the march of progress is never satisfied and the desire to simplify the design merged with the desire to reduce confusion. The new dwarf would be reversed such that the curve would proceed in a high hand direction with the Restricting \ position being reduced in size compared to the Slow Approach / Position. The design was also changed to one with a single large rear access door, possibly enabled through advances in large gasket technology. 

The new style position light proceeded to almost entirely replace the old, especially as the staffed interlocking towers and their electro-mechanical interlocking machines were replaced by CTC starting in the 1970's. By the 21st century left handed PL dwarfs were a rare sight with most appearing at those parts of Amtrak and Conrail territory that had escaped re-signaling since the 1930's. However while out at LINCOLN interlocking on Amtrak's Northeast Corridor in Metuchen, NJ, I spotted a left handed survivor  governing movements out of the MoW yard.

Somehow escaping replacement in the early 90's when LINCOLN tower was closed and re-signaled, LINCIOLN's 5W dwarf is now one of the more accessible left-handed PL dwarfs, mounted on the side girder of the Lake St bridge for all to see.

Hopefully it will escape scrutiny and continue to perform its job for years to come. 

Amtrak's New Position Light Configuration

Following from Pennsylvania railroad practices, Amtrak used the following two configurations for all of its "complete" position color light mast signals at interlockings. They either have a lunar white Restricting \, or they don't. In both cases the single central lunar white Stop and Proceed marker has been retained.  

While most other North American railroads have shifted to using Restricted Proceed in place of Stop and Proceed, Amtrak, and the NORAC rulebook for whom Amtrak is the biggest member, have both retained the Stop and Proceed practice.  

So consider my surprise when saw the recently installed colorized position light signals at Amtrak's new LEGGETT interlocking on the Hellgate Line. The restricting \ is present, but, please correct me if I am wrong, I believe this is the first time I have seen Amtrak PL interlocking signals without a Stop and Proceed marker. 
 

Part of  the Penn Station Access Project, these colorized position lights are the first of many that will wipe out the last stretch of amber position lights on the NEC (PHIL is a point, not a stretch) and they appear to indicate a shift at Amtrak towards that all important stop before entering an occupied block.

In case your wondering the typical Amtrak signal progression is to display a Stop and Proceed if there is an obstruction within the interlocking limits and a Restricting (if available) if the interlocking is clear, but the block beyond is not. The stop certainly seems like a worthwhile safety precaution, but the distinction between it and Restricted proceed is minimal, mostly just the salience of entering a stretch of track with an obstruction or broken rail. 
 

As you can see the new signals on the replacement Portal Bridge have retained the Stop and Proceed marker, but that project was designed and specified some years before Penn Station Access. So it remains to be seen if this is the shape of things to come, or a one off trial. 

 

 

Inside the US&S A-5 Switch-Point Machine

This blog devotes a lot of coverage to the plight of the pneumatic switch-point machine and its long decline since its heyday between 1930 and 1955, but apart from the ka-chug--woosh sound, what makes them distinctive? Well its actually their simplicity compared to their electric counterparts and its that simplicity that made them so competitive with electric point machines despite the overhead of making and distributing compressed air. 

Above we see a Union Switch and Signal model A-5 pneumatic point machine. (An earlier A-1 model also existed and you can tell them in photos because the housing looks like a miniature Quonset hut.) At one end we see the double acting air piston, at the other we see a connection for the control circuits and a blind tube without an air piston, and in the middle we have a fairly plain looking box.

Next lets quickly go over a standard power operated switch layout using some casual terminology. Moving away from the camera we have a stretcher bar that provides rigidity. Next is the throw mechanism that transmits force from the point machine to the points via a rod. This uses a slack coupling so the point mechanism can begin to move and break the static friction. Finally we have the detection rods that accurately detect if the points are hard against the stock rail and communicate that state to the signaling system.

Exposed US&S A-5 pneumatic point machine.

The mechanism can be set up for operation from either side.

Here we see a naked A-5 without its cover on showing off the simplicity of the action. The air piston connects to an action bar which runs through a crank mechanism that transmits force to the point rodding and also its positional state to the circuit controller.

The crank (left) and circuit controller (right).

The coupling between the air piston and the action bar.

The air piston, these came in 3 inch and 5 inch diameter models.

The throw rod couples to the crank assembly. In the photo below this connection is the bolt hole on the stubby arm below the pivot pin. The detection rods sit under the circuit controller have the golden coated nuts on them.

The circuit controller pulls double duty, detecting both the position of the points for the signaling system and also the position of the action bar / air piston, which is sent to the style CP air value unit to cut the flow of air and dump the pressure in the piston. We can see the hind end of the action bar that is given room to push outward under the covering.

The upper two rods provide the actual point detection while I believe the lower rod that extends through the mechanism provides a physical locking function in conjunction with the action bar. When this technology was new that rod would serve the role of the familiar facing point lock.

The goal of the mechanism is to lock the switch point securely against the stock rail even when air pressure in the cylinder has been exhausted, but allow smooth movement of the action bar and points when air is admitted to move the piston. A similar concept is present in firearms where the bolt is locked against moving rearward by the force of gases in the chamber, but is able to be easily unlocked via motion in a different axis.

While I have personally captured video of an A-5 point machine performing a throw cycle, it only showed the points moving along with the admittedly cool sound. However I recently came across a different video from a UK rail museum that has their own flavor of a US&S A-series set up for live demonstrations. Still popular on the London Underground, these instances are commonly used without the protective cover which allows visitors to actually see how the mechanism functions. This flavor of Westinghouse point machine is intended to be set between the rails and has the throw rods moving through the mechanism. The extra circuit controller on the back provides feedback to the pneumatic value.

 

No Approach! The Duality of Uncommon Signals

We all learn about traffic lights in elementary school.  Red means stop, green means go and yellow means slow or caution. These are the basics of automatic block signaling that also tend to get taught in entry level railroading books. Now its pretty logical that a signal might lack the ability to display a clear indication. A permanent stop condition or the end of automatic block territory are both situations where a Clear signal would not ever apply. However there are a few situations where signals in North America can display Stop or Clear, but not Approach on the full speed head. 

The first is at interlockings outside of automatic block territory like a diamond crossing or drawbridge. The signal provides movement authority through the interlocking and without track circuits outside of the interlocking limits there is no "prepare to stop" points an Approach type signal would apply to. Trains will have their own movement authority like a track warrant so a clear signal is basically the interlocking telling the train "you do you". One might expect signals in this case to display a Restricting indication, instead of a clear, and sometimes they do, but that is going to come with a 20mph speed restriction, or less, which can be a time hit on unsignaled lines with higher track speeds. 

The next situation, Manual Block territory, would be very familiar to those in other parts of the world. Although almost extinct in the US, there remains a bit of manual block still in service on the LIRR and the way to identify a manual block signal is the lack of an approach indication. (This also applies in general to historic PRR signaling charts.) Signals will display Stop or Clear Block with any Approach functionality handled by a separate distant signal towards the end of the manual block. The PRR even went one further sometimes substituting the \ "Caution" indication in place of / Approach. 

Sometimes its really not good to have locomotives stopped and waiting at a specific signal,  Maybe there's an issue with a grade crossing, or noise, or diesel exhaust. In this case it would not be desirable for trains to approach that signal prepared to stop, so a preceding signal will either hold trains short or allow them to approach a signal with some sort of proceed indication. The most notable of these is at the entrance to Washington Union Stations 1st St tunnel that the currently diesel hauled northbound trains cannot enter without having a signal displayed further on that allows them to leave said tunnel. Another nearby signal location at CSX's LENFANT interlocking might lack southbound approach signals for a similar reason due to an overbuild.

One somewhat PRR-specific situation is where interlockings are provided with exit signals and because of the short distance between the interlocking's entrance signal and exit signal, Slow Approach is used instead of Approach. This creates an upper head that can only display --- Stop or | Clear. The C&O also made frequent use of exit signals, but seemed to keep their upper head Approach indication, although Medium Clear to exit Approach allowed the C&O to minimize the use of R/Y/Y/ Medium Clear.

A fairly new situation where Approach has been "omitted" involves high speed turnouts. At certain points on the NEC, Amtrak has decided to combine a flashing green "Cab Speed" signal indication with R/*Y* Medium Approach. At the end of a main track that converges into another via a high speed turnout, the result will be an upper head with green and red lamps/positions and no yellow lamp/position.
 

New Signals Up At THORN

 Although not much has changed regarding the ultimate fate of THORN tower, recent photos do show what the new signaling situation is going to look like. In the eastbound direction the triple signal bridge covering tracks 1, 2 and 5 Running, have gotten the Safetrain upgrade with Rule 562 'C' boards turned. Although not yet in photos, it is expected that track 4 will also be getting a PL mast signal to replace the existing reverse direction dwarf. SEPTA is tentatively resuming service to Coatesville upon the completion of new station facilities in 2025 which includes a semi-restoration of #2 track to a point just past the new station for the daily NS regional freight. 

In the westbound direction new PL masts are up on tracks 1 and 2 to replace the reverse direction dwarfs and its assumed that a new gantry mounted signal will be in store for #4 track.  The real surprise is what looked to be a new westbound full PL mast signal on what used to be the Low Grade Freight Line track. The old THORN had maintained a vestigial signal in that same location, but despite the rationalization of the former 6-track full crossover, it seems the low grade stub track has not only been retained, but is being prepared for use. What that use might be remains to be seen, but a mast capable of displaying Medium and Limited speed signals could imply SEPTA trains making some sort of switchback maneuver after discharging on Thorndale's track #4 platform or coming out of some yet to be built storage tracks on the footprint of the old PRR Thorndale facility. 

The THORN interlocking cutover is still planned for later in June with DOWNS to lose its switches before complete removal. GLEN and FRAZER will be turned over to the dispatcher by the end of 2025 closing THORN as an active interlocking station.

Harrisburg Power Office Is Now Mostly Up and Running

When we last checked in on the Harrisburg Power Director's office about a year ago in 2024, the Big Board had been fully illuminated and most of the Westinghouse "Visicode" SCADA equipment had been reactivated with the help of modern technology simulating the presence of the field equipment like substations and such. However, because the 1930's PRR electrification projects had been funded with depression era WPA loans, the PRR had to spread the wealth and about half the office used GE "Code Selector" hardware that was more complex in operation and not as well documented. 

Well between March and September 2024, members of the Harrisburg Chapter NRHS managed to locate the documentation for the GE gear (it was sitting on a storage shelf) and were then able to restore most of the GE panels to operation, which is especially useful that represents the bulk of what was still operational on the old PRR Main Line up through 2013. The GE gear brings the added fun of step switches being used to store digits instead of all-relay registers for the Westinghouse part of the office.

As if step-switches weren't enough, between September 2024 and March 2025, the team also reconnected the alarm lamps and bell which further adds to the effect.

Still to be addressed are the metering circuits along with programmed simulation elements that would allow visitors to participate in directing flows of 25hz power to virtual train movements. Still, the Harrisburg power office  is mostly complete in terms of being "a thing that functions as it once did" so watch out for planned opening dates as the chapter is still trying to figure out how to manage regular hours.

DOCK Movable Bridge to Become DOCK Bridge

In 2017 the great DOCK tower closed as a staffed interlocking station after about 80 years of service. However the imposing structure retained one last official duty beyond "employee lounge" and that was housing the controls and auxiliary equipment to work the adjacent three span vertical lift drawbridge situated between the tower and Newark Penn Station.

 

Unfortunately the Passiac River was not the industrial thoroughfare of years past and unlike the nearby PORTAL bridge whose low clearance made it subject to periodic openings for barge traffic, the height of the DOCK draws is sufficient for the dwindling commercial traffic on the waterway.  After not opening a single time in 2024, Amtrak has petitioned the Coast Guard for permission to permanently close the bridge.

While it is unlikely that anything will happen to the bridge, Amtrak will no longer have to maintain the operating equipment, interlocking logic and the mechanisms used to make and break rail and overhead wire continuity.

DOCK draw actually contains three independent movable bridge spans. A large 3-track north span for mostly westbound Amtrak and NJT trains, a 2 track span for PATH rapid transit trains and a single track span for mostly eastbound Amtrak and NJT trains. The PATH span was set at a higher clearance above the river to reduce the number of openings on what was higher frequency rapid transit line.

 

One interesting quirk was the use of standard point machines to work the rail locking mechanisms at least on the PATH tracks. 

Based on the general interlocking layout I would not expect many signals to move, although the eastbound signals on tracks 2 and 3 might be moved across the bridge to resolve possible ACSES positive stop issues.

The fate of the control equipment on the operator's level and the auxiliary equipment, like AC-DC motor-generators, on the cavernous ground floor remains to be seen, however the safe option would be to leave it in place just in case. Numerous lift bridge have been converted to a fixed status with the counterweights left to dangle for many decades with little thought.

The petition requires a 120 day trial period of being "closed" at which point it will be approved or denied. After that there would be no set timeline for Amtrak to make changes so if a signal move looks likely I'll keep you informed.

Cleveland Line Autos Now on the Way Out

 In another example of either speaking too soon or rolling under the lowering door like Geordi, it has been reported that NS is planning on removing the remaining Cleveland Line ABS Position Lights I recently reported on. 

Scuttlebutt is that NS actually needs the parts to maintain the PL's on the western Fort Wayne Line, however I suspect that after the East Palestine explosion closed the Fort Wayne Line, the lack of PTC on the lower Cleveland may have become an issue. No word on the timeline, but I'll try to track the progress and if the project is a 1 for 1 signal replacement or something that will convert the line from ABS to CTC.

THORN Tower's Last Act

Amtrak's THORN tower has been staffed 24/7 and routing trains on the former Pennsylvania Railroad Main Line since 1938, however after having gone on a rather extensive diet in recent years, THORN tower appears to be entering its last act. However its not going without a few strange twists.

As a CTC era tower with both local and remote relay based interlockings, THORN presents a fairly easy case for remote control, as was the case with THORN's sister tower COLA back in 1987. Already Amtrak has chipped away at THORN's territory, re-signaling CALN interlocking and transfering control to the Section C dispatcher in 2020.  Now it appears that the plan is to re-signal and transfer control of the local THORN interlocking in the middle of 2025.  

While this would typically mean the closing of THORN tower itself, the news is that the tower will continue in service controlling GLEN interlocking via the 1938 CTC machine and FRAZER interlocking on the 1994 vintage unit lever panel. Much of THORN's work involves FRAZER interlocking as that is where SEPTA trains for the busy R5 Paoli/Thorndale service lay over.

Plans also include the removal of DOWNS interlocking with deadhead movements continuing on to THORN. For years track #2 between THORN and GLEN had been in terrible shape with Amtrak operators and dispatchers looking for ways to avoid using it.  However it has been recently rehabilitated and train managers are looking to make better use of the asset. 

With these changes I would expect to see "C" boards for Rule 562 operation on both sides of THORN and if DOWNS is removed it is possible that cab signal only operation will extend all the way to FRAZER (track #1) and GLEN (track #4). Whatever happens, I'll keep everyone informed.