B&M's Centralized Manual Block: The Worst CTC

The Guilford Rail System and to some extent is predecessor Boston and Maine Railroad, had a reputation for stinginess despite being one of the more "interesting" railroads signal wise. In 2014 the formerly Guilford owned Connecticut River Main Line was restored for passenger operation that had been routed off the line in 1987 due to poor track condition.  I took a trip over this route via Amtrak's Vermonter in 2021 and posted a trip report covering the new Guilford style LED target signals, bracket masts as well as surviving instances of searchlights both in Massachusetts and on the New England Central owned portion of the line in Vermont north of the Mass border. However I missed something pretty important in that trip report that only became salient when I was processing all of the photos. Before I try and explain it I'll show a sample of the pre-rebuild Guilford Employee Timetable for the route.

At first view this looks like a pretty common Rule 261/CTC setup, an interlocking, some bi-directional intermediates.  However if you look closely you'll see that each of the two intermediates, shown at mileposts 2 and 7, are distant to the CPR-1 and CPR-9 (not pictured) respectively. That creates a rather unusual 5 mile long block in the middle of the bi-directional single track section that would be broken up by an industry standard 2-3 mile long block. Although this setup was modified in 2014, it was not modified much with a new interlocking CPR-2 eliminating the very long block with a dual distant at milepost 5 for a relocated controlled point CPR-8. The next line segment had a 6.5 mile northbound block replaced with another two 3 mile blocks with the milepost 13 intermediate.  However the third line segment is where things go off the rails again with a massive 8 mile long automatic block between the mileposts 20 and 28 intermediates.

The CT River Line changes ownership at the Massachusetts border reflecting the historic split between the Boston and Main and the Vermont Central.  No matter the ownership however, where the line had been upgraded from Track Warrant/Form D to CTC, the block lengths are reasonable, however wherever the Boston and Main had installed CTC, megablocks are the norm. In fact, on the former Boston and Maine signaled territory controlled by the NECR, the situation is even worse with the intermediate signals acting as single direction distants only similar to Amtrak's 562 cab signal territory, just without the cab signal blocks. The controlled signals in advance of the single track segments are the only indications of block status until the distant signal 2 miles short of the next interlocking. 

This creates automatic blocks of 6 miles south of Putney, 11 miles south of Bellows Falls, 10 miles south of Wapole , 14(!) miles south of Claremont and then a comparatively reasonable 6 miles south of Windsor. North of Windsor a new CTC extension has reasonably spaced blocks of about 3 miles each. At the time of my journey I figured I was just doing a bad job looking out for and photographing intermediate signals, however upon further review I wasn't missing anything, The Boston and Main had employed CTC with manual block distances and setups. If this had been the PRR they could have replaced Clear, Approach and Restricting indications at the ends of sidings with Clear Block, Caution and Permissive Block.

While this sort of layout might seem to be a clever twist of frugality, it is in fact an example of the adage "The Stingy Man Pays the Most".  Not only is the capacity not much better than with manual block/track warrant, ANY track circuit failure in ANY of these super blocks will result in a Restricting signal indication at best or, more likely, a permission past stop signal. The next choice is a 10 mile slog at Restricted speed (elapsed time 30+ minutes) or a dispatcher process to temporarily replace signal rules with TWC/DCS rules if that is even possible thanks to whatever is causing the track circuit problem, like a broken rail. This explains in part why the poor maintenance of the Guilford years formed Amtrak to move off the CT River Line and seize by eminent domain the segment between Vermon and Windsor. Any signal problem would instantly cause a 30 minute delay in addition to all the bad order track. In summary this setup might work for low density lines with some passenger trains that need better protection than track warrants. However if track circuit integrity is taken seriously, this setup is highly fragile. It's no wonder that setups such as this are somewhat more popular with axle counters substituting for track circuit integrity.

Explore French Signaling on the Aubrac Line

 A short while ago, a video on the least used passenger rail station in all of France piqued my interest in the Aubrac Line between Beziers in the south of France and Clermont near the center.  The mountainous line was electrified with 1500v DC in the 1920's and retains much of its original electrification infrastructure including catenary supports and substation buildings.  The line is a good way to see how French railway signaling works in practice as much of the line is single track running under manual block operation with 5-10 mile blocks between stations that also serve as passing points.  Some of the cities along the line night have some shorter automatic blocks so there is some variety.  

The line is also equipped with Le Crocodile ATS system and the more modern KVB balise based system, which is interesting.  Because of the manual block and long gaps between passing points, things can get a bit dull at times, but aside from looking for the 1500v DC substations one can try to figure out if the line uses track circuits or axle counters for train detection.

 In general, the library of cab view videos from Europe is far more extensive than those from the US.  This might be due to the larger number of rail workers and single person operation that limits snitching. Whatever the reasons, its a great resource to help learn other signaling systems.

 

Line of Sight - DART's Third Method

Last year ago I wrote an article on how the DART light rail system in Dallas used two distinct signaling methods.  Automatic Block Signals with Automatic Train Stop  were used on the original Red and Blue lines built in the 1990's and audio frequency Cab Signals without intermediate wayside signals on the Green and Orange lines built since 2000.  However there is a third method first used on the initial segments and most recently employed on the Blue Line extension to Rowlett. This method is Line of Sight operation and while I had seen the signs, I did not fully learn what it signified until I recently had the opportunity to ride the southern portions of the Red and Blue lines that make the most use of Line of Sight.

Line of Sight territory is exactly what it says on the tin.  Trains must proceed able to stop short of any obstruction including other LRV's, pedestrians, motor vehicles, traffic lights, etc.  It is governed by the following section in the DART rulebook.

Line-of-Sight Operation: 

4120 Line - of -Sight Territory Incorporates mainline tracks not protected by ABS/CST. Line-of-sight territory incorporates the following:

• West Oak Cliff Branch - Zoo Station to end of line at Westmoreland Station.
  
  
• South Oak Cliff Branch - Morrell Station to end of line at Ledbetter Station. - Central Business District - Houston Street to Pearl Station.
  
  
• Rowlett - Signal G1813 to Rowlett Station 

4121 Line of Sight Speed Trains must operate at a speed which will enable the train operator to stop short of any obstruction. All special instructions or posted speed zones must be complied with. Speed shall be reduced when adverse operating conditions exist, (i.e.) poor weather. 

4122 Minimum Separation Trains must maintain a minimum separation of at least two LRV lengths unless authorized by the controller or when a train is stored in the tail track. a. No more than one train at a time in the same direction may occupy a city block in the CBD unless authorized by the controller.

When I first encountered Line of Sight Operation at the Garland station on the Blue Line it was accompanied by a two aspect signal that I surmised was part of a low cost go/no-go ABS signaling system.  From the overhead and street view I could identify other signal signals along the line and it seemed that LRV's would approach each prepared to stop within Line of Sight.

It turns out I was only partly correct as these Block Indication signals have their own alternate method of operation. On the two southern routes, Block Indicator signals can work in conjunction with Start Block (SB) and End Block (EB) signs.  Passing Block Indicator with an SB triangle the train is protected by track circuit block until the following EB triangle. I am not entirely sure if the SB is needed before any EB, but that seems to be how it was set up.

The Block Indicators are used where there are line of sight issues like curves and steep overpasses so that LRV's don't have to crawl on these stretches of track.  On the straight and level trains are able to travel on line of sight up to a speed of 45mph. This is of course quite safe as the LRV's are designed to run in traffic and have magnetic track brakes for bus like stopping. When exiting the ABS territory that proceed the Line of Sight territory LRV's receive an "Approach" class indication before the LoS territory sign.

SEPTA two aspect block signals on the Route 102

The DART Line of Sight system is similar to the two aspect signals used on SEPTA's Routes 101 and 102 suburban trolleys, although in that case the signals partly work as a more formal two aspect ABS system. DART Line of Sight allows higher speeds on stretches of track located on median rights of way or city streets governed by traffic signals.  It is worth noting that at least at the time of writing DART trains are scheduled such that only one LRV is expected to be in any LoS section at a time. For example a Red Line train departing Westmoreland is scheduled to enter ABS territory in 11 minutes and the maximum headway is 15 minutes. 

DART's Line of Sight system is a safe and innovative way to achieve cost reductions and enable Light Rail style in street or street adjacent operation with traffic and other non-interlocked signaling. Thanks to the straight jacket of PTC, non-FRA regulated light rail systems are the only place that are able to employ outside the box signaling and safety solutions.

UK Lickey Incline Classic Signaling

I found an interesting video on the manual block setup on Lickey Incline, the steepest Main Line gradient on the UK.  This 2.65% grade stretched over two miles on the line to Birmingham and due to the under powered nature of UK locomotives, most trains, passenger included, would need help getting up.  Although the line was fitted with track circuits, manual block was still employed.  To ease operations, an intermediate manual block signal was provided so that two trains could climb the grade at the same time.  This video details how the blocks were worked and how the helpers were dealt with.



Compare with operations on the steepest main line grade in North America, Saluda.

A Stingy Man's CTC

I'm talked before about various "poor man's" signaling.  Well I don't think anyone could accuse the great Pennsylvania Railroad of being poor, however compared to many peer railroads they were almost pathologically opposed to CTC.  Sure, there were a few schemes like the largely single-track Port Road and Buffalo Line, but where the PRR was using two or more tracks, manned block stations were the name of the game all the way into the Conrail era.

While recently searching around for information on Reading towers, I came upon an interesting resource relating to an interesting manual block scheme employed by the PRR on their Schukyll Valley line between Philadelphia and Reading. This line was one of several built in the late 19th century as part of the PRR's feud with the Reading.  Intended to stab into the heart of Reading territory the line didn't have quite its intended level of success, but ultimately winding its way to the Scranton area, the route was seeing about 18 passenger and 8 freight trains per day in the 1930's.

Click to Enlarge

Unlike the Reading's 2-4 track ABS main line, the PRR's attempt of competition was mostly single track with passing sidings operated under manual block rules.  On the twelve miles of the line centered on Birdsboro, PA there were three passing sidings, each requiring a manned block station that in the depths of the depression, even the likes of the PRR couldn't afford.  While the technology to CTC this type of line had been debuted by the NY Central in 1927 and was also being deployed by the PRR at THORN and COLA, the powers that be decided on a more cost effective solution.

BROOKE tower, note both the PRR and Reading signs.

The jointly operated PRR/RDG  BROOKE tower in Birdsboro controlled a crossing between the PRR line and the Reading's line to Wilmington as well as a number of other local yard and industrial tracks.  Since its ancillary duties prevented BROOK from being closed, the PRR decided to get some value out of the operator there installed a 20-lever table interlocking setup to remote control both the local BROOKE siding and one additional siding in either direction. However if you think that sounds like a CTC island...you would be wrong.

The 20-lever table setup had been reduced to 8 by the 1970's.

First, as far as I can tell the system was direct wire, not some sort of remote code system as typically employed in CTC.  More importantly, there was no traffic control, which is two of the three words that make up the term Centralized Traffic Control.  The operator at BROOK would use the levers to work the remote switches as well as the manual block signal granting access to the next block.  Track occupancy lamps on the table units would confirm the passage of the train.  In fact almost the entire line was covered by track circuits and distant/home signals would provide full block status between themselves and the next manual block entrance (Stop and Proceed being substituted by Caution).

Despite being a bit of a kludge, the system was successful, operating until BROOKE was closed in 1977.  It allowed the PRR to close two manned Block Stations and paid for itself within 3 years.  Why they didn't just go for CTC is still a mystery.  After all the tracks were circuited and the sidings signaled and under remote operation.  My theory is that the PRR was just very conservative when it came to its focus on reliable operation and didn't want to gamble on a technology was not yet fully established.

Hall Disc (aka Banjo) Signals Explained

If a book on North American signaling has a chapter before semaphores that covers stuff like, flag signals, ball signals and tilting targets, Hall "Banjo" signals are often included since they not only look strange, but have also been extinct in the wild since the 1950's.  While hardly forgotten to history, most sources tend to focus on how these signals worked mechanically, as opposed to how they were employed functionally.  The result is that unless one really digs, you are unlikely to know much more about a Hall banjo signal than it was sort of like a searchlight and sort of like a semaphore.  Today I hope to clear up some of the ambiguity surrounding these dinosaurs of North American signaling.

First, how do Banjo signals work?  Hall disc signals were one of the first types to work in conjunction with the revolutionary idea of the track circuit.  Now I have seen some sources associate Banjo signals with time separation systems, and while they could certainly be used in such a capacity, I am going to focus on their use in automatic blocks.  A disc signal (patented ~1869)  is basically a searchlight mixed with a semaphore, before the advent of either electric lighting or electric motors.  Like semaphores, disc signals have a large day indication (the disc) illuminated by natural light, and a small night indication illuminated by an oil lantern.  Like a searchlight, there is a magnetic armature that moves in response to an electric current. When the signal is energized the disc and filter are moved away from the day and night signals changing them from red (or yellow) to clear (or green).  If you can't tell where the disc goes, it is moved up to the 10 o'clock position where a small corner can still be observed.

Some say this is where the term "Clear" signal came from.  Argue in the comments.

The above photo shows a pair of banjo signals in their "clear" state, the colored disc moved up and out of the way to allow daylight to show through. The two state disc signals could be made to display three signal states be using either a distant-home configuration (as is still popular in Europe) or by mounting two heads on the same mast, one displaying Red and Clear, the other Yellow and Clear.  Clear/Clear = Clear, Clear/Yellow = Approach and Red/Yellow = Stop (and Proceed).

This rare color photo shows a Hall disc signal actually doing its job.  As you can see the colored discs are actually pretty effective.  In a time before electricity, these would be a high tech alternative to mechanically operated semaphores. This also explains why Banjo signals are so often associated with the Reading system.  In the late 19th century the Reading was an extremely wealthy railroad and would be able to afford something that would be like CBTC today.  As ABS became more prevalent, disc signals fell into the same category as 2-position lower quadrant semaphores,a commodity technology which lasted into the 21st century on some former Southern Pacific lines.

Now it is time to put together the final piece of the puzzle.  Above we see an arrangement that was only possible within a fairly narrow sliver of time.  Reading Hall disc signals are on the same mast as mechanically operated semaphores.  What is going on here?  Well the disc signals that are designed to work with low power, primitive track circuits are providing an automatic block signal indication, while the mechanical semaphores are worked from a nearby interlocking tower providing the route protection. 

 

Here we see a slightly different scenario where we have two position semaphores for trains moving torwards the camera, the top mounted semaphore for a straight route, the middle semaphore for a diverging route and then the low mounted call-on signal.  Then we see the Banjo for trains moving away from the camera as ABS exit signals. The semaphores can be directly controlled from a mechanical lever frame, displaying either Clear, Medium Clear or Restricting, and any ABS modifications given by the Baljo signals when the train departs the interlocking limits.  So Medium Approach would be Medium Clear entrance to Approach exit.

I am by no means an expert on all the ways these signals were employed, but I do know that one can't simply dismiss them as proto-searchlights or glorified semaphores as is often the case in so many books and museums.  Hall disc signals needs to be understood in the context of a manual block world devoid of even the basic electronics that would revolutionize railway signaling in the 1890's.  They were cutting edge technology employed by only by those railroads that could afford to be early adopters.