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.
Amtrak has recently activated Rule 562 cab signal operation between OAK and BUSH interlockings on the Aberdeen peninsula in Maryland retiring three intermediate wayside signal locations in the process. This follows a similar project between PRINCE and BACON interlockings that took place in 2018.
The three wayside signal locations are the Milepost 65 signals just north of the Aberdeen station, the Milepost 67 signals near the defect detector in Short Lane and the Milepost 69 signals in Perryman.
This project has been anticipated for the better part of a decade, but according to my sources was waiting on a larger project to build a new interlocking or interlockings to improve routing around the Aberdeen station. It is possible that with both the Susquehanna River Bridge and Baltimore Tunnel replacement projects now underway, Amtrak lacked the spoons for a new Aberdeen interlocking.
The Pennsylvania Railroad Main Line, today operated by Amtrak as their Harrisburg Line, is known for its many interlocking towers that survived well into the 21st Century and I have covered several of them on this blog. However there is one "place" that isn't quite a tower, although it has many of the trappings of one. While the PRR seemed to have an aversion to CTC, it still had a lot more signaling infrastructure than peer railroads with a particular focus on Manual Block System and its related component, the block station. What's a block station? Well its a location on the line that can host a block operator who in turn can perform those duties necessary for some (manual) block operation like transmitting train orders, displaying signals and throwing hand operated switches. Even on signaled PRR main lines one could find non-interlocked block stations open either 24/7 or part time.
Located at milepost 56.7 between PARK and CORK interlockings on the Main Line is the town of of Leaman Place. You might recognize the name for being the interchange point for the Strasburg Railroad. This segment of the Main Line was electrified in 1939 and at the time featured 4 main tracks. Despite the 24 mile gap between the two interlocking stations, no intermediate crossovers were provided as most disruptions could be dealt with by relying on the "spare" main track (with the parallel Columbia Branch directly providing an additional two tracks of relief capacity for freight). However in 1948 tracks 2 and 3 were removed due to declining traffic and evidently this length of single track operation during maintenance or equipment failure had become an issue because in 1961 the PRR constructed the new LEAMAN block station at milepost 57.0 with a pair of main track crossovers protected by semi-automatic signals. Unlike similar hand throw block stations LEAMAN had no normal hours of operation and was only open as needed for single track operation.
LEAMAN consisted of a pair of center locked hand operated crossovers and a pair of position light signals oriented in the normal direction of travel. As this was not an interlocking, no reverse direction signals were not installed. A rather robust operator's shelter was provided and outfitted with station signs, climate control and telecommunications.
This sort of hand operated crossover layout was not uncommon on other double track ABS main lines with the requisite "shelter" typically taking the form of a wayside telephone booth that would allow crews to call the dispatcher to pick up their movement authority to run through the single track area or to report clear of it. However LEAMAN was unique in that its signals and electric switch locks were tied to a small control panel inside the operator's shelter and not accessible to road crews.
If you are looking at older versions of the NORAC signal aspect chart you might notice something a bit odd. Most of the common signals indication have a dwarf option for situations with restricted clearance like tunnels or terminal areas. Because of the understandable choice to limit dwarf signals to 1 or 2 elements, some uncommon aspects like R/Y/G Medium Approach Medium are omitted, however until 2018 NORAC also omitted a far more popular signal, Rule 285 "Approach". For those of you who have been living in a cave, Approach, also known as "Caution" in the UK, is "the yellow light" in railroad signaling. A signal so basic that it appears in elementary school books on how trains work. How Rule 285 was neglected in dwarf form is an interesting story of path dependence.
The story begins with the lamp color yellow performing double duty as for the Restricting indication. When shown alone on a dwarf signal, yellow Restricting, not Approach, so Approach has to be something else. Well, we have two lamps so why not make Approach Y/R? Well dwarf signals are most often used in terminals, terminals are slow so dwarfs really need a Slow Approach indication. Single lamp *Y* flashing yellow exists and is the preferred option, but back in the day flashing relays were expensive and unreliable so we should probably have a fixed version of Slow Approach. This is where the fateful choice was made. R/Y Slow Approach could have worked. If the Red lamps burns out the signal becomes a Restricting, but the rules boffins likely didn't want R/Y Restricting on a high signal to be confused with R/Y Slow Approach on a dwarf signal because that mistake would likely result in an accident. Therefore dwarf R/Y was given to Restricting, Y/R was given to Slow Approach and Rule 285 Approach was out of luck.
Slow Approach on Track 1 east at CP-97 instead of Approach.
For the sake of correctness NORAC did offer Rule 285 Approach in the form of a PRR pedestal or a B&O dwarf CPL, but these were never options in color light territory or after position light signals began to be phased out. So what was a railroad to do when it needed Rule 285 in a restricted clearance situation? First option was to use Slow Approach, one loses 15mph within interlocking limits, but outside of interlocking limits the rule becomes "regular" approach with a Medium speed limit. The second option was to use Y/*R* Medium Approach, this bumps the speed passing the signal up from Slow to Medium, but ultimately suffers from the same drawback as Slow Approach in that trains can't come at either of these substitutes on a Clear, trains have to hit an Approach Medium or an Approach Slow first. From my field observations Medium Approach was the preferred alternative and could be displayed on either a 2 or 3 lamp modular stack by lighting the yellow lamp and flashing the red below it.
To be fair, the Seaboard system used by CSX also exhibits this problem despite using only using lunar for Restricting with dwarf Y/R for Slow Approach and R/Y for Medium Approach. By forgoing a flashing medium approach CSX lost its latitude for an "easy" dwarf approach aspect. However it was ultimately NORAC that cracked first and in 2018 they adopted *Y*/R as the dwarf option for "straight" Rule 285 Approach. While this now leaves Rule 282a Advance Approach out in the cold, Approach Medium is pretty much a lossless substitute. Of course these sorts of changes can take some time to filter down and it was only recently where I managed to catch one in the wild at SEPTA's WAYNE JCT where a dwarf has replaced a high signal at the end of a platform.
With this change the ball lands back in CSX's court. Will they make some basic changes to its system like adopting *Y* Advance Approach in addition to *Y*/R dwarf Approach? Or will they keep looking for more "Canadian Combinations".
Starting off with the IHB, this was a Conrail subsidiary that was later split between NS and CSX. It continues to white on blue Conrail style station signs although in a different font and often mounted on signal gantries or cantilever masts. In a more recent development the interlockings bracketing Gibson Yard, CP-COLUMBIA and CP-GIBSON, have used a Penn Central font with eastbound CP-COLUMBIA in Conrail blue and CP-GIBSON and westbound CP-COLUMBIA in PC black.
The EJE, since merged into CN, likely had the most distinctive terminal railroad station signs with green on orange lettering that would typically include the railroad's "The J" logo.
The BRC, owned jointly by all 6 US Class 1 railways, makes do with a small stencil on the hut or nothing at all. This strategy is shared by the TRRA in St. Louis, although historically a TRRA logo sis appear on some towers.
The KCT has generally aligned with its local Class 1 KCS using large black lettering on a white background. Historically the wide tower signs had "KC" on either side of the station name.
This is similar to the New Orleans Public Belt which had similar white on black signs on the two interlocking towers it controlled, EAST BRIDGE JCT and WEST BRIDGE JCT, at either end of the Huey P Long Bridge.
As far as I am aware that's the current state of station signs for the mid-continental terminal railroads as of 2025.
In September of 2024 CSX added two new signal rules to its rulebooks, Limited Approach Limited and Limited Approach Medium, and examples of both are just starting to appear in the field. In fact I believe this is the first use of a non-cab signal related multiple lamp flashing signal in the United States. If these rules and multi-flash aspects sound both strange and familiar at the same time its because these sort of "combination" signal rules are a standard thing north of the border in Canada.
Since the steam era our friends up north have taken the concept of speed signaling to a bit of an extreme with every possible combination of one speed going to another speed given an explicit signal rule. You want to go Slow Speed to Limited and Limited to Slow, Canada has you covered.
Everywhere else in North America has realized that this extreme amount of signal rules is dumb and will lead to confusion and higher training costs. While some combination indications like Medium Approach Medium or Medium Approach Slow occur frequently enough to be worth including, the remainder are unlikely to see much use and are better off being substituted for (for example downgrading Limited speed combinations to Medium) or covered by special rulebook instructions like NORAC famously allowing trains to diverge over an Approach X type signal indication if the previous signal was not Clear. Anyway it looks like CSX has thrown its lot in with the Canadians and started to care that trains keep that extra bit of Limited Speed when diverging back to back.
Limited Approach Medium was spotted at on A-Line at SOUTH MICRO where southbound Amtrak Carolinian Train 79 will make an early divergence to its eventual turn off at SELMA with the NORTH SELMA crossovers in between. While the NORTH SELMA crossovers are Medium Speed, T79 would be taking a straight route there so many they just wanted to get it slowed down early for the tight turn onto the H-Line an additional mile beyond. Youtuber Danny Harmon managed to catch a Limited Approach Limited at 10TH ST interlocking on the Vitis Sub. He was also puzzled as to the purpose as the next two signals in the northbound direction were intermediates at standard 2 mile intervals.
Anyway if you would like my opinion of these new signal rules, necessity aside CSX did a good job picking from those signal aspects that were available to them. Despite CSX's major screw up picking R/Y/G as Medium Approach Slow, which forced Medium Approach Medium to use R/Y/*G*, that mainly presents a problem for a potential Medium Approach Limited. Using R/*Y* for these Limited Approach X signals jives with CSX choice of R/*Y* for Limited Approach. Thus we have Rule 1281-D R/*Y* Limited Approach, 1281-E(?) R/*Y*/G Limited Approach Medium and Rule 1281-F(?) R/*Y*/*G* Limited Approach Limited. (Note I could not determine the actual CSX signal rule numbers at this time so those are my best guesses).
The evolution from "Stop and Proceed" to "Restricted Proceed" in North America is long and something I hope to tackle at a later date. A holdover from the timetable and train order era where waiting for a train running ahead increase its lead made some sense to reduce collisions, the fuel and time savings of allowing following movements to keep moving is hard to deny. However even where Stop and Proceed are the norm, exceptions are necessary where something like a stiff grade might make restarting a heavy freight train difficult. To implement these exceptions, the (G) or Grade marker was used on automatic signals to relieve some or all trains of the need to stop when paired with a Stop and Proceed indication.
Stop and Proceed was especially popular in the Northeast United States, but after Conrail was picked apart by NS and CSX, most of the major northeastern freight territory fell under the spell of Restricted Proceed. At this point the G marker appeared to be on its way out as the remaining NORAC roads were either passenger focused or too small to have signals or heavy freight trains. However, as the limited speed triangle, Amtrak's Harrisburg line turned into an unwitting refuge. The PRR's Main Line between Philadelphia and Harrisburg was surprisingly hilly and saw more than its fair share of automatic signals with (G) markers applied.
One might assume that the spread of Rule 562 cab signals without intermediate wayside signals and complete lack of through freight would put the Main Line's (G) markers into a terminal decline, however at the Milepost 21 intermediate signal, a minor capacity project may have what could be the last new main line (G) marker to be installed in the United States.
When Amtrak wanted to upgrade the single direction tracks tracks between the SEPTA Yard at Frazer and the start of 4-track operation at Paoli, they modified Milepost 21 intermediate signal location for bi-directional operation on both tracks with new Safetran colorized position lights and (G) markers in the eastbound direction. Moreover, the (G) even uses the same old school blocky font as opposed to the smoother letter used on things like (D)istant and (A)pproach markers.
It's anyone's guess how much longer these (G) markers will be around for as the track segment they govern will soon be subjected to the Rule 562 treatment. Another part of Amtrak territory south of Wilmington also features both long freight trains and (G) markers, but it too going the 562 route so its a good chance that these will be the last new (G)'s installed in the United States.
While out visiting METRA TOWER A-2 at Chicago's Western Ave for the first time in many years, I noticed that the US&S H-2 dwarf searchlight signals at the adjacent TOWER A-3 interlocking had been replaced by L&W LED searchlights with a small backing target. It is unclear if this took place in conjunction with the 2019 removal of legacy PRR position lights at TOWER A-2. TOWER A-3 is remote from a panel inside the staffed TOWER A-2 and the interlocking's other distinctive features including gantry mounted main line searchlights and A-5 pneumatic point machines had been left untouched. You can see the difference between the old H-2 searchlights and newer LED dwarfs below.
An interesting feature is that the 6L dwarf appears to illuminate only with a route is lines (or I assume upon the occupation of adjacent track circuits). This signal is placed after a train exits the main line, but before it is routed to a yard track. I managed to catch the 6L LED dwarf displaying a flashing red "Restricted Proceed" indication for a yard move, in conjunction with a lunar white Restricting aspect on the 10L gantry signal. (Note the 10L signal displays "3rd head Restricting" with a phantom center head.)
I assume that the H-2 yard dwarfs always displayed R stop or L Restricting and the LED units changed this to *R* Restricted Proceed as is the style today. I guess its cheaper to have an LED unit with just a single color of LED's, but I will point out that Union Pacific did choose to use lunar LED searchlights at the nearby KEDZIE interlocking.
