Limited Triangles!

 A little while ago I mentioned NORAC Rule 280b Approach Normal, a signal indication that has been effectively extinct in the wild for over two decades. However we will look at another marker type signal indication that used to be fairly widespread, but as far as I can tell, has now been reduced in the United States to just a pair of locations on the former PRR Main Line. Of course I am referring to the limited speed triangle.

Introduced sometime around the 1940's, the bright yellow Limited Speed Triangle was deployed on speed signaled railroads in conjunction with the introduction of the #20, Limited Speed turnout. For the uninitiated this translates to speeds of about 40-45mph. Prior to this speed signaled railroads tended to have a main line Normal (Maximum Authorized) speed of  50-70mph, a Medium (aka Reduced) speed of 30mph and a Slow speed of 15mph. The system worked from both a track engineering standpoint given the speeds involved and logical standpoint in terms of full speed, half speed and quarter speed. As equipment improved throughout the 1920's and 30's, the gap between the maximum speed trains could regularly achieve and the 30mph Medium Speed began to grow. Because its easier to decrease running time by not going slow as opposed to just going fast, a number of Eastern railroads invented both faster turnouts and the concept of Limited speed. 

#20 Limited Speed turnout at BRYN MAWR interlocking.

Just like in the 1980's when High Speed 60 and 80mph turnouts were invented, railroads suddenly had to fit the round peg of a new speed into the square hole of their existing signaling system. In a time when flashing signal relays were generally shunned as unreliable the solution was the Limited Speed Triangle. The black bordered yellow triangle would upgrade Approach Medium and Medium Clear indications to Approach Limited and Limited Clear. In cases where a #15 turnout was being replaced by a #20, the signaling change would involve change to interlocking wiring or logic. 

Although some railroads including the Reading, did invent new non-flashing limited speed color light signal like Y/G/G or R/G/G, limited speed triangles were embraced by the PRR, B&O, L&N, ACL/SAL and Southern. They also appeared in Canada with the addition of the letter L inside the triangle. Of course one of the biggest users of the triangles was the PRR, which would employ them at select junctions and along its 4 track main lines that features frequent non-reverse running crossover movements.  More specifically the PRR deployed limited speed upgrades (and triangles) to places where its 4-track lines would shift orientation from ⏬⏬⏫⏫ to ⏬⏫⏬⏫ and also as part of its general World War 2 era NEC re-signaling effort.

DV Interlocking with a mix of Limited and Slow speed diverging routes.

Starting in the 1950s flashing signals became more accepted and the Limited Speed Triangle began its slow decline. The main downsides was the inability to mix Limited and Medium speed routes, the issue of Approach Limited indications proceeding Medium Approach and the reduced visibility of the triangle vs a color light, especially at night. By the dawn of 21st century I was only aware of two remaining installations of limited speed triangles. The first was at COUNTY interlocking on Amtrak's NEC in New Brunswick, NJ with a full set of four triangles at the interlocking itself and the milepost 31 and 34 automatic locations adjacent to it. These were unfortunately replaced in the early 2010's as part of the larger 562 re-signaling effort between COUNTY and FAIR near Trenton.

 

The other use of limited speed triangles, and the only one still in service today, were the milepost 8 and 11 automatic signal locations adjacent to BRWN MAWR interlocking on the name brand "Main Line" portion of the Amtrak Harrisburg Line. These two signal locations are adjacent to the Ardmore and Villanova stations respectively and easily photographed. The reason BRWN MAWR itself lacks the triangles is because the tower caught fire in 1994 and the interlocking redone with modern hardware including flashing relays. The two distant locations will certainly keep their triangles until the Main Line between ZOO and PAOLI is slowly re-signaled over the next 10-20 years.

 

Note I have been invoking the United States instead of North America in terms of the endangered nature of these signals.  That is because Canada still retains quite a few of its Limited triangles generally on its western transcontinental routes at the ends of single track passing sidings. Highly ironic that the land that hasn't seen a flashing signal indication it doesn't love, has become the final refuge for a hack intended to avoid flashing signals.

MBTA Re-Signaling Project Reaches Lowell

An update for my previous reports on MBTA's re-signaling efforts on Boston's north side commuter lines.This project consists of installing cab signals and Rule 562 operation on all or part of the North Side lines as well as the general replacement of GRS SA-type searchlight signals. In fall of 2020 the project had already commenced, but there was no sign of it at CPF-BY in Lowell when I stopped by for a visit. 

In fact I even documented ongoing maintenance work on what appeared to be brand new replacement SA heads.

Well recent photos indicate that the re-signaling work has no only reached CPF-BY, but also also replaced the GRA SA searchlight dwarfs with L&W LED searchlight dwarfs, which I guess is better than Safetran cube stacks.

At this point there is no information about CPF-LO, CPF-WA and CPF-NC located beyond the end of MBTA operations at Lowell, but before the end of MBTA ownership at CPF-NC. I suspect this might become a signaling sanctuary as CSX would want to avoid needing to run cab signal or ACSES equipped leaders here and the MBTA would want to hold out for Federal rebuild money to extend service to Nashua.

CPF-NC in late 2021 showing no signs of change.

Additional reports indicate that CSX has dropped new signals at CPF-309 and/or CPF-307 which would be in line with their plans to assimilate the old Guilford territory.  No word if the new signals are CSX standard hoods or Guilford/MBTA targets and also if CSX is planning to run Rule 562 as all Boston Line locomotives will be cab signal equipped and multiple sections of the old Freight Main Line will have MBTA cab signals.

SEPTA Suburban Trolley Signaling: Past and Future

Light rail is currently the locus of signaling innovation in North America due to its mix of limited regulation, low budgets and legacy systems.  For example I have previously written about DART's three different signaling methods in use on its light rail network. In Philadelphia, one such legacy system is the suburban trolley lines running out of  69th Street terminal on the western Philadelphia border. Similar to Pittsburgh's south hills light rail lines in concept, the method of operation is currently being converted from a basic trolley era ABS system, to a hybrid CBTC system.  As I just managed to pick up a bunch of new photos, I figured it was a good time to cover both systems while they are still in the transition period. 

Route 101/102 block signals at 69th St

The ABS system inherited by and later updated by SEPTA as necessary, was a 2-block affair with signals displaying proceed (green) or stop (red). Although there was one location, Drexel Hill Jct, that could be described as an interlocking with full signal protection and a power operated facing point switch, the entirety of the Routes 101 (Media) and 102 (Sharon Hill) were run under traditional ABS rules with hand throw crossovers and spring switches entering sections of single track. 

Two aspect ABS signals at a Route 101 hand throw crossover including operator hut.

 
The single track segments were handled with an automatic tumbledown scheme and the one junction was fitted with a three lamp signal and a route selection punch box. Where a diverging move was encountered a yellow signal indication would be displayed. There was also no ATS or ATC enforcement of signals or speeds. 

Legacy yellow diverging aspect at east end of Route 101 single track segment.

Due to the sections of street running and close spacing of stops, the Suburban trolley LRV's are considered to have sufficient braking performance to dispense with an Approach type indication. Signals are approached prepared to stop and when the next block is cleared, the following movement will get a clear signal to proceed. Not all of the route miles are protected by signal indication with the street running and other slow areas working on sight. These sections are partly defined by "end of block" signs. 

Route 102 switch protection signal paired with a single track block entrance signal.

In addition to the two lamp ABS signals, there are/were switch position indicators and reverse direction protection for the single track sections and Drexel Hill Jct. When entering single track and exit signal would follow the spring switch to protect against a race condition if two opposing trolleys were to attempt to "seize" the single block at the same time. 

Route 101 single track switch signal with block entrance signal in distance.

Starting in 2019 work started on a new CBTC based signal system that would also make use of sizable number of interlockings to replace hand throw crossovers and single track spring switches. As of early 2022 the CBTC system had not yet entered service so the interlockings were used to supplement the existing ABS signal system. 

New SEPTA Suburban Trolley cab display unit with CBTC disengaged.

In fact on the combined section between 69th St and Drexel Hill Jct there were sufficient interlocked crossovers to supplant all of the ABS signal locations! As many of the ABS block signals have so far remained on the routes past Drexel Hill Jct during the transition period, it is anticipated that the CBTC will provide full block separation, not just a safety overlay.

New Route 101/102 combined trunk interlocked crossover and block section signal.

All in all the project involved the addition of 10(!) new interlockings, three crossovers on the combined Rt 101/102 trunk, Drexel Hill Jct, one crossover on each Rt 101/102 branch, three Route 101 single track endpoints and one Route 102 single track endpoint. In addition to these interlockings, three additional holdout signal locations were installed in proximity to an interlocking.

New interlocked holdout signal at entrance to Rt 101 single track territory to accommodate short turns

Another interesting new feature is the provision of a yellow fixed ATS transponder adjacent to each fixed absolute signal.

Yellow ATS transponder located between mast base and rail.

Although I was unable to observe every detail of the current operation it appeared that the new wayside interlocking signals were backwards compatible with the old ABS system displaying R - Stop, G - Clear, Y -Diverge. The presence of a 4th lamp hints at at the presence of a lunar white indication that will either be used for a "cab speed" (most likely) or an absolute block / restricting signal.

Same location as above prior to rebuild with spring switch and yellow "end of block" sign indicating start of line of sight operations.

Although the new CBTC/CTC system is modern and high tech, it never the less exhibits the limits of technology to deliver substantive performance gains. Ten new interlockings along with 20 or so miles of CBTC will cost more to maintain than the legacy ABS system. Furthermore, the speed control function will almost certainly decrease performance from current standards. On the other hand contingency operations will be greatly improved with track work becoming possible during operating hours and vehicle/overhead line failures now able to be worked around without the need for temporary block operators hand throwing switches. In theory the capacity of the system will improve, especially on the route 101/102 combined trunk, however the decision to run more frequent service has always been limited by the budgets and political will of both SEPTA and various levels of government. My assessment is that operations will say the same, liability will decrease along with speed and the impact/cost of contingency operations will decrease enough to offset the high cost of the new signaling system, at least until the point that the technology becomes unreliable.

Death by 1000 Cuts: The NYCT Subway Slowdown

 Starting in the 1990's, the New York City Transit Authority (NYCTA) started a process to slow down the largest subway system in North America, ostensibly in the name of safety. Over the next two decades the process, conducted slowly and out of public view, went from costing riders a few minutes here and there to triggering a full on capacity meltdown as the system, despite its decreased performance, benefited from record ridership. Transit Twitter and Blog personality Uday Schultz has recently completed an exhaustive history of the great slowdown and the science of transit speed control in general. It's a great read and starts with a zero based explanation of the NTCYA's trip-stop and timer based ABS signaling system up through the events that triggered the management action and the subsequent slide into dysfunction. Still, while this piece does a great job explaining why, it comes up a bit short explaining "why". So lets dive in a bit.

One shot GT timer signals added to CANAL ST interlocking before re-signaling.

In the early 2000's everyone in the NYC Subway fan community was aware of the performance decreases and would track how the NYCTA seemed to seek out any location where trains could get moving and just find ways to throttle service back to a plod. Even in locations with no infrastructural changes the trains were operated with an appreciable lack of urgency. The community was full of theories as to why this slowdown was happening and, to a lesser degree, why nobody seemed to care. After all other cities, even those with traditional signaling systems like Philly, Chicago and Boston, found ways to achieve brisk acceleration and top speeds of 55-70mph, making the 25mph crawl of the NYC Subway a distinct outlier. 

SEPTA Broad Street Subway Express train @58mph.

As Uday's article covers (read it now to avoid spoilers), the speculation the early 2000's fan community was both right and wrong at the same time. They were right in that most of their theories were correct.  They were wrong in that there was no one reason that bore primary responsibility for the problem. The newer equipment, up through R68, did have slightly better performance than those the signal system was designed for. The new composite brake shoes did have slightly worse performance than the old iron shoes. The system did rely on train operator rules compliance and related management thereof to ensure safety. Then, between 1991 and 1995 all of these factors combined in varying degrees to cause four significant accidents, opening the NYCTA up to both liability and public pressure.

Inbound Williamsburg Bridge ramp with carlength long grade timer blocks.

The response was similarly multi-pronged from slowing rolling stock down in both acceleration and top speed (55 to 40mph), ubiquitous use of intermittent speed control devices, curtailment of restricted speed operation and harsh punishments for trip stop engagement. Much of this action plan was implemented over a period of 20 years so casual riders didn't really notice the decline in performance. The cherry on top was that the intermittent speed control devices were then allowed to drop below posted thresholds making operators wary of even trying to follow the posted speeds. This is what caused the opportunity to get a skilled operator and a "good run" to vanish over the course of the 2000's, especially as the pre-90's workforce that learned to run trains without speedometers, gradually retired. 

All of this background leads to the real question, why did ostensibly high level management decide that such a drastic decrease in performance was acceptable? This is important because in an age when getting the public to *want* to choose public over private transport, the performance of public transport is increasingly throttled by policy leaving private transport as the only option that can attempt to offer speed and convenience. Well, lets put on our 1991 hats and see what management may have been thinking.

1. The most salient factor was the long term plan to equip the NYC Subway with a full time ATC/ATO system, later realized with the selection of CBTC to replace the wayside signals, timers and trip stops. Investment in an end-of-life signal system would be wasteful and performance decreases could be argued as temporary.
   
   
2. After peaking at 2 billion annual riders in 1948, the shift to non-urban living and private transport dropped ridership by over half with the peak of NYC's crime wave coinciding with the subways trough of ridership. The system was running at half capacity so "slightly" increasing trip times was likely not seen to be a big deal.
   
   
3. Decades of disinvestment had caused the NYC Subway to fall into a prolonged state of bad repair. With limited funds compelled trading performance for safety.
   
   
4. The threat of continued accidents was a political liability while small overall changes in performance would be unlikely to generate much if any notice let alone political pushback.
   
   
5. The reliance on operator skill presented not only the continued risk of accident, but would also put up pressure on costs as said skilled workers had to be trained and retained. Uniform operations according to the speed control systems would make operators fungible and require a lower skill floor.
   

These 5 factors could be arranged multiple ways to create a compelling policy proposal to management. It would have taken an extraordinary amount of personal risk for any of the top officials to insist on maintaining performance standards when CBTC was right around the corner anyway. I think the decisive element was the NYC Subway consistently running at half capacity for over two decades. It's not even that signal system capacity *could* be reduced with little impact, but that the 900 million annual ridership seemed to be both a floor and generally baked into the city. If local New Yorkers were willing to risk their life to ride the system, an extra few minutes wasn't likely to deter them either. To some extent management was proven correct, their slowness campaign only became a problem after ridership doubled over the following 20 years.

If you want a take away its that reducing performance has, is and will be the go-to fix for even rare safety problems. We've seen this with PTC and we've seen this on other transit systems like SEPTA and WMATA. The changes are rarely publicized and the public rarely objects even as they unconsciously sour on rail transit and make the switch to private vehicles. After the service meltdown NYCTA did set up a speed improvement task force that has been fixing the mis-calibrated timers and raising speeds that were subjected to overly conservative calculations. Still, while the rollout of CBTC has allowed for increased performance profiles, it would be interesting to calculate if they match what was achievable by human operators working under a system with a slightly greater tolerance for risk.

PS: An interesting comparison can be had with how the UK responded to the Ladbrook Grove Rail Crash of 1999. The crash program to install TPWS at select locations was similar to NYCT's system-wide modifications, however as far as I can tell, it had minimal impact on train operation, perhaps in part of the UK's continued reliance of train drivers' compliance with rules to ensure safety, as opposed to technical mechanisms.

A History of Amtrak's 562 Distants - From Concept to Removal

It was reported in Railway Age that Amtrak has filed to remove its wayside distant signals installed at 10 locations on the former PRR Main Line (currently referred to as the Harrisburg Line) between Parkesburg and Harrisburg exclusive. While this move caught me completely off guard, I cannot say it is exactly surprising given more recent developments along the line. Amtrak's application is full of appeals to PTC as a rationale, however that's pretty much the regulatory equivalent flattering the teacher. At this I'd typically cut paste a boiler plate plea for people to go out and get their photos while they can along with an assessment of my own ability to get photos (which is pretty good BTW), but instead I will dive a bit deeper on the history of Amtrak using wayside distant signals in cab signal only territory in general and the Harrisburg Line in particular.

Fist of all I want to normalize the use of Rule 562 as the shorthand for "Cab Signals without fixed intermediate wayside signals" method of operation. While this is a NORAC specific rule, cab signal only operation is most closely associated with NORAC and just saying "Rule 562" is a LOT more concise. For those who are unfamiliar, Rule 562 operation it means that between interlockings train movements are governed only be cab signals. At interlockings wayside signals are retained to physically display information for operational efficiency, in case of cab signal failures or other contingencies. There can also be special cab signal realted signal indications to support this operation, most notably the Rule 280a and Rule 280b modifiers "Clear to Next Interlocking" and "Approach Normal".

This method of operation first appeared on the PRR Conemaugh Line in the late 1940's, although a few railroads like the CNW and CNJ also did some 562 experiments about the same time. The method didn't really take off until the 1970's with the Long Island Rail Road and then the 80's with Metro-North, Conrail and Amtrak. Despite not being a NORAC member, Metro-North was the first to really innovate in this space as it looked to do something about the truly ancient signaling it had inherited including copious amount of semaphores. Intermediate wayside signals would be removed, interlockings would have full wayside signals with the "C" board for Rule 280a and wayside distant signals approaching interlockings would also be retained with an "N" board that would display when the "C" was displayed at the interlocking itself.

The process was simple, a train that suffered a cab signal problem would be given the Rule 280a absolute block, "super clear" indications and when approaching the next interlocking it wouldn't even have to slow down provided a Rule 280b was displayed at the distant.  Moreover the wayside distant would provide the necessary speed information for the lined route at the interlocking. Approach Medium with a lit "N" meant the non-cab signaled train would slow for a Medium Speed route with a Rule 280a "C" displayed. Delays would be avoided and all the commuters would get home happy. 

Metro-North reduced aspect wayside signals.

Well it turned out that Metro North found this system to be a bit overkill given the frequency of cab signal failures. They found it to be so unnecessary that they converted to a reduced aspect signaling system with just 3 indications: Stop, Cab Speed and Absolute Block. On the other hand in the early 1990's when Conrail was going all in on the Rule 562 concept, they decided that they liked the additional flexibility of CISC interlocking signals for their unwieldy freight trains, but the Rule 280b concept was a bit too much and wayside signals would appear only at interlockings.

Conrail era 562 territory wayside signal with 'C' marker.

Amtrak's first big foray into Rule 562 was the Shore Line between New Haven and Boston. In conjunction with the 150mph Acela service, the entire route would require a top to bottom re-signaling with Rule 562 as the method of operation chosen for much of it. Perhaps as a reaction to operational problems encountered on Metro North territory, Amtrak decided to install wayside distant signals in advance of its Shore Line interlockings. Although a few instances of Rule 280b "N" boards did appear, they were never placed in service. This brings up the motivation behind the distant signals if they had limited utility in a cab signal failure. Without Rule 280b they would be mainly informational about the state of the route ahead allowing crews to correct mis-routes or employ better train handling than was possible with surprise cab signal drops, especially for freights. For example slowing quickly and then coasting towards a Stop signal in hopes it will clear before a complete stop is required. At worst they might give crews of cab signal failed trains the impression that they did not have to approach the next interlocking prepared to stop (although today ACSES does enforce Rule 280a if cab signals are cut out).

Shore Line Milepost 133 distants with turned 'N' markers.

Amtrak next employed Rule 562 for the high density signaling system used between Newark and New York Penn, but here the nature of high density cab signaling didn't lend itself to the concept of any wayside distant.  Wayside distants did make a second appearance on the ~2005 Harrisburg Line modernization project between PARK and STATE interlockings with a total of 12 wayside distant locations being installed around PARK, LEAMAN, the old CORK complex, RHEEMS , ROY and STATE interlockings. Due to the new PARK interlocking being the boundary between 562 and Rule 251 (ABS) territory, the westbound track #1 562 distant was left bagged for when the re-signaling was expanded. This would turn out to be the last Amtrak Rule 562 distant to go up and one of the first to be removed.

Amtrak's following Rule 562 projects on the NEC, Hudson Line and Springfield Line would all drop wayside distants completely. Back on the Harrisburg Line in 2017, when STATE tower was closed and the interlocking rebuilt for high speed movements, the associated wayside distant at Milepost 101 was quietly removed instead of being altered to display new signal indications. When Rule 562 was extended from PARK to CALN and THORN, the bagged distant at Milepost 44 was also removed. So as 2022 comes to a close, it is clear that Amtrak has passed on the original NORAC Rule 562 concept of wayside distant signals providing seamless recovery from cab signal failures and they have felt this way for some time. 

The affected wayside signal locations on the Harrisburg Line are located at milepost 55.3 (Tk 1&4, LEAMAN wwd), 59.2 (Tk 1&4 LEAMAN ewd), 64.5 (Tk 4 HOLLAND wwd), 66.1 (Tk 1 CONESTOGA wwd), 70.8 (Tk 1 CORK ewd), 71.8 (Tk 2 LIDITZ ewd), 81.5 (Tk 1&2 RHEEMS wwd), 86.0 (Tk 1&2 RHEEMS ewd), 92.3 (Tk 1&2 ROY wwd) and 96.4 (TK 1&2 ROY ewd).  Of these the most notable loss will be the Milepost 59.2 signals located at the old Irishtown Road crossing on an original PRR era overhead signal gantry. 

Still, many of the rest are accessible and also worthy of being documented so get out there over the next year while the wheels of regulatory approval turn.