A blog devoted to explaining the ins and outs of North American railroad signaling, past, present and future. This blog seeks to preserve through photo documentation the great diversity and technical ingenuity of 20th century signaling and interlocking hardware and technology. Related topics cover interlocking towers and railroad communications infrastructure.
Note, due to a web hosting failure some of the photos and links may be unavailable.
Well a major holdout of classic signals is now gone. Just south of the Ohio River on the route of Amtrak's Cardinal, the juncton of the former C&O and L&N main lines had featured both B&O and C&O signals until just a few weeks ago. One of these, at NX Cabin, was the last C&O signal bridge left on the old C&O Main Line between Newport News and Cincinatti.
This island of signaling had survived because it was involved in a re-signaling programme in the 80's or early 90's and was lower down on the priority list. The main attraction was KC junction, which feature a number of 5 orbital CPL's and some strange hybrid C&O signal bridges that were refitted with B&O CPLs during the re-signaling process. The ones coming off the former C&O main line were notable for their comically large sun shade.
KC junction also featured a massive 3 story L&N interlocking tower, but it was demolished sometime within the last 10 years. I do not know the state of the CPLs at the adjacent OB Cabin (Ohio Bridge) or A interlocking in Cincinatti, but the smart money is that they have also been removed.
From time to time I have brought up some of the quirks inherent to North American light rail signaling systems. Because they exist in a regulatory and cost grey area (not really railroads, not really subways, able to stop on sight in traffic, etc) the signaling systems they employ tend to be very economical. Well this past summer I traveled to Denver and rode around on its extensive light rail network. There I noticed that the RTD light rail had methodically checked off every box on the light rail signaling checklist and I figured I should share it here.
1.) Missing Wrong Direction Signals
See that little red circle? Yeah, that's plated as a signal because the RTD's commitment to single direction ABS is so complete that all wrong direction movements need to get talked past the stop disc at the next interlocking.
2.) No Distinction Between Auto and Interlocking Signals.
See any difference between the ID plate on the interlocking signals in the first picture and the ABS signal in the second? No? Well that's par for the course on a light rail system.
3.) ATS
Light rail systems don't uniformly lack speed and signal enforcement. They just opt for the budget versions. RTD Light Rail has some sort of loop based ATS on its main line sections, but the operators weren't too helpful in providing the details on how it worked. Of course where ATS proves impractical one gets a nice little sign.
4.) Single Headed Signals.
Light rail systems hate confusing drivers with multiple signal heads, so flashing aspects warn of diverging movements.
5.) Vehicle, Signal Thyself
Dispatchers cost money, so LRVs simply set their destination and let track mounted sensors do the rest.
6.) New Lines, New Rules
How can consultants bill those hours if they just say to stick with the same old thing? Of course the line that just opened in 2017 would have some new signal rules requiring a second head!
7.) US&S N-3's
You look hard enough around a large light rail system and you'll find a US&S style N-3 signal head š
Did I miss any? Throw something in the comments and I'll see if I can find an RTD example ;-)
In the late 1930s the Pennsylvania Railroad decided to equip its low grade Columbia and Port Deposit Branch with a state of the art signaling system in conjunction with an equally cutting edge electrification project. The Rule 261 signaling on a single track line with passing sidings was controlled by CTC machines at just two on line towers, PERRY and COLA. Remarkably this signaling lasted over 80 years with the northern half being retired in 2012 and the southern half being retired on April 9th, 2018. Fortunately I had been able to fully document the line as it originally appeared over the preceding decade and a half and you can review my work here.
Compared with other recent NS re-signaling projects that have continued through multiple calendar years, the PRR signaling on the lower 20 miles of the Port Road were replaced in about 6 months. Not only were the remaining PRR position light signals replaced, but NS also decided to convert the cab signaled line to Rule 562 operation, eliminating four automatic signal locations and converting another to a controlled point. Of course I don't need to tell you all of the changes that took place between PERRY interlocking on the NEC and CP-MIDWAY because NS is nice enough to publish comprehensive change documentation that also includes all possible signal aspects.
Starting from Amtrak territory at PERRY, the first major change was the conversion of the former CP-MINNICK interlocking to a new CP-MINNICK controlled point. CP-MINNICK used to provide access to the west end of the Perryville freight yard and was downgraded to an automatic signaling location when the yard was removed. Well, for whatever reason NS decided to install a controlled point cantilever mast in between the two former CP-MINNICK home signals. I guess it allows locomotives and trainsets to be reversed at the Perryville wye track without having to tie up the entire stretch of track south of CP-QUARRY, where NS likes to store trains waiting to get onto the NEC. It could also be a way for the signal department to add what is functionally an automatic signal despite a possible management directive to go Rule 562. Without the signal at CP-MINNICK, crews cannot tell if they are approaching a Slow Approach or a Stop signal at PERRY from their cab signal alone. The aspect chart also shows how the distant to CP-QUARY on the siding track has to display both Approach Limited for a Limited Clear and an Approach Medium for a Medium Approach. Also being wiped away are electro-mechanical cab signal code generators of the type that existed at the cab signal cut between CP-MINNICK and PERRY.
The once and future CP-MINNICK
Moving on, CP-QUARRY has had its eastbound home signal moved to be closer to the switch. Evidently PTC and cab signals are a substitute for sight lines. Also, NS is taking a play from the Amtrak playbook and having trains diverge over Medium Clear at CP-QUARRY approaching a Medium Clear/Approach at CP-TOME and Limited Clear approaching a Clear/Approach signal at CP-TOME.
I recently stumbled upon a YouTube channel run by an old Amtrak conductor who posted a number of video narrations of various parts of the Pennsylvania Tunnel and Terminal Railroad (Penn Station, Sunnyside Yard, etc) including the towers and signaling. The videos were shot prior to the mid-90's when the old towers and old signaling were still in place.
Here in this discussion of the Penn Station track layout, one can see some interrior footage of A Tower starting around 4:30
This video show Sunnyside Yard has some footage around Q tower a little past 3:30.
Here is another Sunnyside video with some Q tower content right up front and some R tower inside footage after 8:00
These are the ones with the most tower content, but her has a bunch of other tour videos that are still very interesting. Check them out!!!
Well NS just cut in the CTC on the former Conrail Reading Line, however the original "Reading Line" was the Reading railroad Main Line between Philadelphia and Reading. Eventually folded into the Conrail Harrisburg Line, running between Philadelphia and Harrisburg, the western end was given the CTC treatment pretty much on the NS/CR border in 1999/2000. However, the portion between Reading and Philly was largely left in it's ABS Rule 251 State barring a few bits and pieces here and there.
The All New CP-FORGE
NS has already gone about replacing most of the former Conrail ABS small target searchlights with Darth masts, and then embarked on a re-signaling project that has gone from CP-FALLS to CP-PHOENIX (exclusive). However a few searchlights and Rule 251 remnants hold on. Still, a new crossover is in evidence at CP-BIRD and just a few miles north of there a new crossover is going in at the future CP-LORANE.
The biggest loss, besides the whole concept of single direction ABS, will be CP-TITUS, which is pretty much still in it's 1960's Reading System configuration, complete with a movable point diamond. Needless to say, that i currently my top target for documentary preservation. Hopefully things will move slowly, as they did with the Reading Line, however one has to be prepared for the unexpected, like with the Allentown Terminal complex. Don't pass up the opportunity to get out there while you can.
Wow, so it took nearly 2 years, but the short, 30 mile long NS Reading Line has finally been "upgraded" to bi-directional Rule 261 operation, replacing the former Conrail small target searchlight signals. Fortunately, over the course of two marathon trips I was able to document most of the signals between CP-WEST LAUREL and CP-ALLEN, inclusive.
The Reading Line and I go way back, it being the site of one of my very first interlocking surveys all the way back in 2002 and later captured in this blog post on CP-ALBURTIS. I later surveyed the Reading Line from the back of an Amtrak fall foliage train in 2016, returning a few weeks later to document the west end and then about 6 months after that to cover the east end. Incidentally, the re-signaling will also come with an increase in speed from 50 to 60mph, with NS now making full use of its Class 4 track. Speed increases are rare events, even after a re-signaling effort as it requires the re-timing of every grade crossing on the route, whereas normally they can be left alone. This may have accounted for the protracted timeframe of the project.
I want to thank my friend Kevin, a Reading Line local, for being my guide and I want to direct everyone over to his own photo album of the signaling changes over the last 2 years. It's a damn shame to see another stretch of increasingly rare ABS bite the dust, but at least we did everything we could to capture what it was like.
So it's come to this. I'm so desperate for filler content that I've taken a page from the Forgotten Weapons playbook and started posting book reviews š General Railway Signal's (GRS) Elements of Railway Signaling (or at least this version) was published in 1979, on the 75th anniversary of the companies consolidation. It is an industrialreference book similar to Babcock and Wilcox's "Steam: It's Generation and Use" and is likely targeted at electrical engineers who are looking to enter the railway signaling field or at least manage it. No publisher information is listed and it appears to have no ISBN.
The book is exceedingly comprehensive, covering everything from basic track circuits to CTC systems and NX interlocking schemes. It also covers all sorts of obscure topics like approach lighting and hump yard retarder systems. When one reads the word "Basics" in a title, one might expect a focus on "basic" operations. Big easy to read diagrams of Automatic Block schemes and grade crossings. This book is more an inch deep and a mile wide, providing a basic explanation of pretty much every railroad signaling topic.
Ultimately this is where the book can fail a reader with no or only casual electrical engineering experience (and no, not the digital kind that everybody is learning today). For pretty much every signaling topic one can think of, the book provides a paragraph or two, a diagram and then moves on to the next topic. There has been very little effort given to actually trying to provide intuitive explanations and a lay reader will probably need to make more than a few passes.
Ultimately a reader will gain insight into why (classic) signaling works the way it does, however there are so many ways to do similar things that without further information one will not be able to tell how any specific piece of railroad is signaled. Moreover, with a date of 1979, there are a lot of things that are not covered like solid state relay replacements and data transmission that uses packets instead of simple frequencies and polarities. Still, it's a very valuable reference for anyone who is looking to understand how things worked in the pre-digital age and Railway Signaling is far more accessible than something like Color Television or Telephone Switches. After all, relays are pretty much digital devices.
Because of it's "not really published" status, the book is hard to find at typical online booksellers. Ebay is your best bet with final sales prices ranging between $20 and $30 before shipping. These books also can be found at train shows with a typical price of $40.
