Caught on Camera: Double Green Clear

 With the CSX takeover of the former Guilford Rail System empire, there's a real risk that we might see the end of double green clear signal indications in the wild. Most commonly associated with the New York Central, double green clear is an artifact of two position ABS semaphore signals with an upper head of R+G and a lower head of Y+G resulting in the combination of R/Y for Stop and Proceed, G/Y for Approach and G/G for clear. A part of the NORAC set of signal indications, its last common use was in New Englande on the former Boston and Main territory operated by the Guilford Rail System and the MBTA.

As previously covered, while Guilford wasn't perfect it did maintain a bunch of legacy signaling practices, like bracket masts, up into the 21st century. Even in places where new signals were being installed, two head "distant" signals to interlockings would still display G/G as opposed to G/R. In fact you can see it for yourself on Google Street view on the milepost 2xx intermediate signal adjacent to the Main St grade crossing in downtown Saco, Maine. 

Lit for an approaching train we see double green clear displayed on a thoroughly modern target type LED mast signal. In fact I saw this street view while scouting Guilford automatic signal locations on Google Maps and was not only able to locate the normally dark (approach lit) signal, but catch it displaying the coveted indication for a northbound Downeaster train. 

Unfortunately it appears that this location will be replaced by CSX within the year with no chance of it retaining the double green clear. However with 5 round trips a day, its pretty easy for anyone in the area to  catch it for themselves. 

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.

Exit Stage Right - Leaving Signaled Territory

Typically I write about railroad signaling, occasionally touching on non-signaled block systems such as TWC or DTC.  Each are more or less straightforward on their own, but things can get interesting when transitioning from one to another, specifically from signaled territory to non-signaled territory.   the three primary methods are:

1. Exiting at a Manual Block signal
2. Exiting over Restricting
3. Exiting at a sign

Although some of these have a few additional complexities that I will go into below.

WINSLOW Jct on the PRSL had two exits into Manual Block territory.

 Under mostly defunct manual block systems, trains would be admitted to the block by a manual block signal, typically under a modified Clear indication like Rule 280 Clear Block in the PRR Rule book.  These signals would be located at the start of manual block territory directly after the interlocking or on the last signal on a route that could lead to manual block territory.  A signal less favorable than Clear Block would be preceded by an Approach-type indication.

NORAC Rule 290 Restricting into DCS territory.

With the coming of Track Warrant systems like Conrain's Form D Control system (DCS), trains moving from signaled territory to DCS territory would be given a Restricting indication, regardless of the trains DCS movement authority.  In fact this method of operation was written into the text of NORAC Rule 290.

Proceed at Restricted Speed until the entire train has cleared all interlocking and spring switches (if signal is an interlocking or CP Signal) and the leading wheels have:

1. Passed a more favorable fixed signal, or
2. Entered non-signalled DCS territory

 This is also the standard when trains are moving into a yard or non-signaled sidings, although in those situations the train is entering Restricted speed track as opposed to a non-signaled block system.

Seaboard Rule 290 Restricting into Collier Yard.

In addition to placing the Restricting signal at the entrance of the interlocking, it can be placed on an exit signal allowing higher speeds throughout interlocking limits.

Exiting at a sign means that signaled territory ends at a sign instead of a signal.  This can be used with signaled approach blocks to allow reverse direction trains to occupy the approach block without needing to get a track warrant, as seen below on the old D&H near Saratoga Springs, NY.

 

Where signaled approach blocks are not present, the exit sign can be used at the end of interlocking limits.  As with the Restricting exit signal, this allows a more favorable indication, such as Approach or Slow Approach, to be displayed at the start of the interlocking.  This in turn allows higher speeds for pretty much the cost of a sign and also better supports non-restricted speed track as, unlike the Restricting signal, Restricted speed is not necessarily required if the train possesses non-signaled movement authority.

NJT ARCH interlocking eastbound home signal.

Recently a more radical take on the exit sign has started cropping up.  Instead of treating the signal as a virtual restricting signal demanding an Approach-class signal in advance, some railroads, including Norfolk Southern, have been configuring their interlockings to display Clear-class signals into an end of signaling sign, even if that sign is located at the interlocking limits.

For example, at CP-PORTER, shown above, the main track signal displays Approach for a straight route towards Restricted speed track marked by a sign at CP-PLANT.  However it also can display Slow Clear for the diverging route directly into a Track Warrant territory (Rule 171) sign at CP-PORTER's southern limit.   The only other option is Restricting if the route is occupied within the interlocking itself.

Trains being signaled into Yard Limits directly north of CP-PORTER get an Approach-class signal on the straight route, but a Slow Clear on the northeast wye track.  While all this inconsistency can technically be considered safe as the signs technically overrule the preceding Clear-class signal.  Still, I am not a fan of this practice as it is important to never violate the contract that a Clear-class signal provides two clear blocks ahead and an Approach-class one clear block.  Unless approach blocks are being used, a signaling system has no idea about the state of the track in unsignaled territory and a Clear-class signal would be writing a check the signaling system cannot guarantee.

LIRRs Insane Absolute Block Signals

Back in May I wrote a post covering the LIRR's new Reduced Aspect system.  Similar to Metro North's, the system uses some additional indications involving slow speeds as well as the color Lunar White to distinguish it from existing color light signals.  I was somewhat puzzled why, after adopting a new color light system to replace the older position light system, the LIRR would create a brand new system from scratch as opposed to just expanding, or using its color light system.  After all,  NORAC has had this down for years with the "Clear to Next Interlocking" modifier or the use of a Cab Speed signal with a Restricting option for failures.

In fact, I had heard that the LIRR had been using the "Flashing Green" aspect to indicate Absolute Block Clear.  It had never seen it, but it made sense.  Not to mention they had Manual Block Clear as an existing option as well.  A quick google search actually found a previously unknown LIRR signal rule reference.

NAME: Absolute-Clear.

INDICATION: Proceed; Track clear to next interlocking signal. Approach next interlocking signal prepared to stop.

Yeah, there you go.  If you want to go to color light, just use *G*/R. A nice uniform difference from NORAC Cab Speed.

Huh?  *G*/*R*?  That's a bit...odd.  I guess they really want to make it different from anything that might appear in the Amtrak zone?  Wait a minute...what's that in the text of Rule 298B?

Absolute Medium Clear?  Absolute Slow Clear? Oh no..

 NAME: Absolute-Medium-clear.

INDICATION: Proceed; Medium Speed within interlocking limits. Track clear to next interlocking signal. Approach next interlocking signal prepared to stop.

Are you kidding me?  This is the sort of think a child would come up with for their imagination railroad.  Oh wait, it gets crazier.

 NAME: Absolute Slow-clear.

INDICATION: Proceed; Slow speed within interlocking limits. Track clear to next interlocking signal. Approach next interlocking signal prepared to stop.

Yup, that is a flashing three headed signal. I mean I guess I see the logic.  The LIRR doesn't use flashing signals outside of the Amtrak zone so this associates flashing with an absolute block while not duplicating any existing signal aspects.

 NAME: Slow-approach

INDICATION: Proceed approaching next signal prepared to stop. Slow speed within interlocking limits

Ok, I guess that brakes the pattern.  Wait, on the PRR Slow Approach can stand in for Slow Clear on high signals.  What does the LIRR do there?

NAME: Flashing Slow-approach.

INDICATION: Train will proceed in accordance with signal indication within interlocking limits and after clearing the interlocking, proceed under absolute clear indication to the next interlocking.

They named a signal indication "Flashing Slow Approach".  I guess the other three signal rules used up all their creativity juice.  The fact that I only became aware of all this now just shows the extent to which the LIRR keeps its operating practices under wraps.  To be fair, this isn't as crazy as it appears.  Like I said, when this was developed in the 1970's the LIRR had avoided flashing signal aspects and also wanted to avoid conflicts with Amtrak zone signals (although there was and is no wayside-free operation in the Amtrak zone).  In the relay hut logic could use a single flashing circuit applied to the entire output of a signal when an Absolute Block signal was called for AND the system avoids the odd case of a "Clear to Next Interlocking" displayed along side an Approach signal, which can happen under NORAC despite being redundant.

This here is how you do absolute block.  End of discussion.

Ultimately it doesn't matter if the system makes sense when viewed at the right angle on a sunny day.  In a recent Newsday article, LIRR operating personnel were complaining that the new reduced aspect signals don't give the engineer enough warning, that train handling and/or the ability to maintain a schedule will suffer.  The Pennsylvania Railroad, the Long Island Rail Road's corporate parent until 1968, SOLVED this issue in the 1940's with the 'C' marker which simply modifies an existing signal aspect. The root of today's limited aspect problem is that in the 1970's, instead of adding one extra marker light and one extra signal rule, the LIRR decided to add 4 signal rules and 13(!) different indications to implement a cab signal system without fixed wayside signals and now trying to change it over to something like the NORAC method with color lights likely would lead to confusion. 😵

Metro-North started fresh in 1983 and first choose the PRR solution.

The rank and file of the LIRR have always prized a complex rulebook that is shrouded in secrecy in order to increase job security and overtime.  40 years later the management is now having to take drastic measures, beyond a simple color light conversion, to bring order to the chaos and unfortunately I suspect that all the old vestiges of the train order and manual block systems are likely to be next.

New NORAC Signal Rules!

Yes, and before people get all nit picky yes NORAC is indeed adopting both new rules and a couple new aspects that go along with old rules.  All of the new changes have in fact been used for many years by a number of member railroads as system special instructions and moreover they have also been seen in other railroad signaling systems.  This is a nice example of a signal rules committee looking at the state of the art and deciding not to keep its head buried in the ground.

The new rules were made effective in the 11th edition of the NORAC Rule book released on Feburary 1, 2018. I've been a bit busy since the start of the year so I just hadn't noticed until now XD

We begin with Rule 281a, Cab Speed, which has been modified to include SEPTA's *G*/*G* dwarf indication which it has been using for about the last 10 years.  Also included was a PRR pedestal indication probably because of some situation on Amtrak.

 The next change plugs a major hole in several eastern signal aspect systems in that there is often no Approach indication available on dwarf signals. Y/R is Slow Approach, Y is restricting and for years NORAC had to make up with displaying Y/*R* Medium Approach for straight routes.  However there was one obvious solution and after appearing on the Conrail SAA timetable as a special instruction for years, *Y*/R has been adopted as Approach.  CSX please take notice.

A bit more consequential is the long overdue adoption of Medium Approach Slow.  Unlike CSX which had reserved R/Y/G for M-A-S forcing R/Y/*G* for M-A-M, NORAC went with a nod to the PRR using R/Y/Y.  This aspect had long been used in by the MBTA in the Boston area and possibly also on the former Boston and Maine territory. More recently it had been incorporated into Caltrains new speed signaling system in 2003. Note, NORAC Rule 283b does not include the "when first becomes visible" admonition, which I would suspect is something they are trying to get away from.

Finally in a weird nod to the Seaboard Coast Line, NORAC has adopted Limited Approach  signal as Rule 286a.  However, unlike the CSX Rulebook which is a bit ambiguous about when a train must slow to Medium Speed, NORAC Rule 286a states that Limited Speed applies only through the switches and turnouts, then Medium Speed applies.  Like Rule 286 Medium Approach, trains must begin reduction to Limited Speed as soon as it becomes visible.  I suspect this might be used to claw back a few seconds where trains had previously been stuck at Medium Speed due to a far-yet-visible Medium Approach indication.

All in all these are sensible moved by NORAC.  The real question continues to be when CSX will finally adopt *Y* Advance Approach!!