PTC in track warrant territory?

[SleepyCat]

Hi Matt! Sorry for the long duration since my last post but…been busy. The only recent developments I’ve seen on the Stone Mountain Georgia line are the changing of power lines from the old poles feeding the old wayside signals to the new poles feeding the new wayside signals. Also, they have already installed the electric switch locks at both ends of the Avondale yard and have readied the boxes at both ends of the Stone Mountain siding for transition to the new PTC overlay control system. However on the Abbeville subdivision in Tucker they have replaced a T-20 hand throw switch with and electric power switch for a siding. The Tucker line new boxes for PTC have Verizon dishes installed on them. I wonder why the Georgia line doesn't and if it has something to do with the nature of TWC/ABS for the line or/and the Pulse Coding that is used? Theoretically they could stop the trains for emergency conditions via the pulse code in the rail going into the cab rather than by the roof mounted units receiving signals via GPS. I will send you pictures as I obtain them.

[MattW]

Indeed, I saw them installing the box at the north end of Avondale the other day. Also, I discovered that the new signal heads have a little color band on the back indicating what color each "lamp" will show. So for instance the signal protecting Kirkwood southbound on the right-hand (when southbound) track is G-Y-R over G-Y-R over G-Y-L-R (I think anyways) while the new Scottdale signals are G-Y-R over L-R. I imagine the rest of the two-headed signals are similar, but I haven't been in a position to look closely at them since I "discovered" this.

[MattW]

Following on from my last post. I was able to take a good look at the signals at 153 and 154 (SE Stone Mountain). The SB signal at 153 is G-Y-R over Y-R. The SB signal at 154 is G-Y-R over L-R. Neither of these make sense to me. At 153, the only aspect that makes sense is advance approach. Why is that needed when the next signal is the intermediate at 151, then the "absolute" at the NE of Lithonia at 147? I thought Advance Approach was used in places with short signal blocks to give more stopping distance, that hardly seems needed for a 2-mile then 4-mile signal block entering another subdivision which is track warrant territory unless CSX has installed a signal around 149, the subdivision point. I also don't understand the restricting at Stone Mountain, I could understand it northbound protecting the little storage siding there, but why southbound? Can anyone explain these oddities?

[SleepyCat]

Dear MattW:
A LOT has been happening on the Georgia Line lately regarding development of PTC. I have it from reliable sources telling me the whole line from Atlanta to Redan (Phase 1) is expected to go ‘digital’ by the middle of September this year and that satellite dishes ARE going to be installed on boxes along the Georgia Line by the end of the week (September 18th 2015); we’ll wait and see. One of these sources explained to me quite simply that when the sensor on the locomotive detects the train beyond or ahead of where it is supposed to be along the APB (Absolute Permissive Block) route they will be forced to stop courtesy of the interface for the designated block via the new system. This still falls ‘short’ of CTC where the entire length has controlled signals as opposed to automatic block and, where with CTC powered turnouts exist as opposed to manual hand-throw. The reliable source said that in the new system in essence, there really isn’t ‘Dark Territory’ anymore as trains can be detected by satellite. You may have also noticed that they (CSX) have added a lower hat signal to the ‘flower pot’ signal #1566 located alongside Ponce DeLeon Avenue between Juliet and Stone Mountain Industrial roads (I have attached a jpeg showing it – as usual, it is turned sideways until operative). They have also installed NEW antennas on the new stainless steel boxes in Stone Mountain, Panola and Redan. These antennas are meant for ‘back up’ radio in case primary means of communication fails. Remember that digging being done at the Lithonia yard months ago? That was the installation of a new septic tank because the county accidentally ‘plugged’ the sewer connection from the road to the building. Fancy that!
Vinnie.

[MattW]

Hi Sleepycat, it's great to hear from you again! It's interesting that it's expected to go live mid-September which is...now. Then again, the Abbeville line cutover seemed pretty quick too. I went by Scottdale today on my way home and noticed the same backup antenna installed. I haven't been by 1566 recently, but that makes a little more sense that it now has a second head, do you know if it's for restricting like Scottdale and SE Stone Mountain or advance approach like 153? I'll try to get down that way tomorrow myself.

Also, that's hilarious about the Lithonia depot sewer!

Cheers!

[SleepyCat]

Dear MattW:
Sorry I was away for a while – family business and that sort of thing. I suspect the need for the two hat signal system is in part due to the need for an Absolute Permissive Block System protecting train movements between sidings. The first in Scottsdale protects trains entering the Stone Mountain block against collision through Stone Mountain siding. Track Warrant should be sufficient but the APB was introduced over standard ABS as a secondary safety feature back in the 1990’s to handle trains diverted from the CSX Florida mainline. However PTC must necessitate the second lower hat as an overlay. So what we have here is PTC as an overlay for APB that is an overlay for TWC. Remember that ABS permits higher capacity in TWC. The second hats no doubt will remain operable during train movements but in standby mode until protection is actuated by a possible conflict. It’s the only scenario I can see to govern train movements with a second hat because in both APB and ABS a second hat is unnecessary unless at interlockings. At Clarkston the signal appears to be an intermediate (single hat) and this is the last signal before the one in Stone Mountain with the newest lower hat, on final approach before the siding. WHY there is a lower hat leaving the Stone Mountain siding when there is another, little over a mile into Redan I do not know unless it’s because both signals are APB (note how neither has a number plate; this indicates that they are APB – the one on Panola has ‘G’ for ‘Grade’). The signal at Redan whose number plate I can’t remember is NOT an APB.

I spotted the addition of a reconditioned/repurposed ‘Flower Pot’ signal box on Laredo drive and have attached TWO pictures one before the other after. I’m sure it plays some significant role in the PTC development. I also have attached a picture of a Verizon Wireless satellite DISH attached to the Scottsdale utility-control box. As of this writing my brother Joey noticed the new lower and top hat signals have been turned in the direction of traffic but still have a tarp to cover them. It appears CSX may actually soon be ready to retire the old Seaboard three position lights and US&S Searchlights. I for one will miss the old US&S.

Sleepycat.

[MattW]

Yep, I drove Conyers to Scottdale today myself. All the new heads are turned and bagged. The dish at Scottdale doesn't look connected yet, the wires aren't real orderly. Either way, we're close to the cutover.

[SleepyCat]

Someone told me that CSX is ready to cut to the new signals this Saturday. As of this writing there are only THREE dishes yet to be installed he said, one at Redan, another at Stone-Mountain Lithonia and lastly SE Stone Mountain. VZW dishes have already been installed at Kirkwood Jct near East Lake Marta Station and the new signal adjacent to Marta Inman Park Reysnold Town Station.

[SleepyCat]

Dear MattW;
Well I spent the better part of an hour during the afternoon of last Saturday the 10th observing CSX work crews breaking in the new PTC signal system. Crewmen were stationed at all signals, including the bungalow boxes controlling wheel detector at Shadowrock and switch-lock turnouts at Avondale. On my way home from work in the morning hours on the MARTA line heading eastbound I noticed CSX removing the US&S searchlights at Kirkwood junction near Eastlake MARTA station. As I watched signal operation along the Georgia line around 2:00 pm I met and talked with a fellow rail fan named Ivan at signal 1566 in Stone Mountain, near Goldsmith road. I learned quite a bit.
Ivan has considerable more experience than I do on CSX signals and explained that CSX signals are crafted for speed restrictions while Norfolk Southern signals are implemented with route selections in mind. Ivan educated me on CSX signals by consulting one of their rule books. To begin with let me tell you what I noticed. The first signal I watched was the absolute signal at the SE Stone Mountain exit. This signal has the normal three aspect green, yellow, red on the top hat and green, red on the lower hat. It was displaying yellow indication on the top hat and a blinking green on the lower hat. According to CSX rule C1281B this means ‘Proceed, approaching next signal not exceeding Limited Speed’.
After that the next signal I witnessed was #1529 near Southland Homes, formerly ‘G’ under the old operation. It has the aspect of green, yellow, red on the top hat, yellow and red on the lower hat. Today it displayed yellow on the top hat and yellow on the lower hat. According to CSX rule C1284B this means ‘Proceed, approaching next signal not exceeding Slow Speed’. Ivan told me this would be an ‘advanced approach’ signal for the next signal at Redan, essentially letting the engineer know to proceed to the next signal that will be on approach.

The signal at Redan #1509 was indeed ‘approach’ and the next signal after that as you know is the Lithonia Automatic Interlocking near Marbut Road. It of course was red for complete stop and, because it is an absolute signal it will only clear the route once there are no conflicting trains ahead of it, between sidings after Lithonia.

Lastly the signal at Stone Mountain near Goldsmith, #1566 displayed Green over Red indicating ‘clear’. So this is what it looks like to me; the signals are operating according to what Lithonia Automatic Interlocking is ‘telling them’ under today’s test procedure. Because Lithonia is red, signal #1509 at Redan is yellow. Because #1509 is yellow signal #1529 at Southland is giving an advanced approach in dual yellow. Because #1529 is signaling advanced approach, the absolute signal at the Stone Mountain siding exit is displaying proceed for limited speed in preparation for #1529. Signal #1566 marks the route clear up to the absolute.

WOW. NOW things are beginning to make sense. Under this modus operandi the signals, in conjunction with Track Warrant provide complete protection and with the satellite dishes installed and the receivers atop the locomotive hoods, not only are engineers provided plenty of warning but forced to stop in an emergency as well.

SleepyCat.

[MattW]

Wow Sleepycat, thanks for the great info! I'm quite a bit shocked by SE Stone Mountain showing Approach Limited, but sure enough I went back by today and the color band on the back of the lower head is green, I guess the lighting wasn't so great the last time I looked and I thought it was blue for lunar. The signal was dark when I was there, but there was a CSX truck parked. I made it as far as Redan at the 151, and it and 1529 were lit showing the same progression as your pics: Advance Approach to Approach, they were so beautiful! In the other direction, I went as far as the NAS Kirkwood in the other direction. Do you know what the lamp in the lower head there north of Stone Mountain is? Today the color band looked kind of yellow for another advance approach, but there's no legal way to get close like there is at SE Stone Mountain and the 1529. There was also a truck at the intermediate in Decatur which was dark. I don't know what the ultimate plan for approach lighting is, but speaking strictly as a railfan, I hope they keep Redan and 1529 lit and light up the others Scottdale being a controlled signal, I expect it to remain lit full-time as it was with the searchlight signals.

I have to say, I never thought I'd see any more than the basic three-aspect signaling system in-place along the ex-Georgia road mainline, especially not something like Approach Limited, what's next? Sneaking a medium-approach-medium in somewhere? I'm still a bit puzzled why CSX would go to the trouble of the advanced signal logic when they're still using track warrants. If a train isn't cleared through Lithonia, they would know it and stop there south of the 151 like they do now to avoid tying up any grade crossings. I do have a sneaking suspicion that they will eventually go to CTC all the way to at least the 149, either adding a new signal (hence the advance approach at 1529 since it would be a short block between Redan and the subdivision point) or making Redan the last controlled signal. All in all, these are exciting times for our little rail line!

[SleepyCat]

Your input is good as always MattW! Yesterday Wednesday my brother witnessed a long cargo train heading westbound past the absolute signal at SE Stone Mountain and was surprised to see it ‘yellow over blinking green’. Herein lies the tale of the inflexibility of ABS and to some degree APB systems. Matt, I did talk with a CSX crewman who informed me that although the line is Track Warrant it is not exactly ‘Dark Territory’ and that ‘the board’ can see trains as far as Lithonia.

Another crewmen told me that with the implementation of PTC, they have gone Digital from Redan to Circle Track Atlanta, thus explaining the retirement of the former ABS signal at Lafrance Avenue and the dwarf signals at Lafrance and Arizona Avenue. Apparently while CSX has no immediate desire to implement CTC to Lithonia they want to go half-way with the ability to observe operating conditions, although I have heard from several different CSX crewmen they feel it will not be much longer before CTC is installed to Lithonia.

Roy DePriest, retired engineer with CSX told me years ago that with digital signals in the tracks, beginning in Clarkston, it should be possible to observe them with cab signaling. I’m sure most, if not all CSX locomotives have cab signaling installed.

As far as signal #1566 is concerned your guess is as good as mine. I did take a picture of it the same day as the three others and it was Green over Red. For now I am including a picture of the Absolute Signal in Scottsdale Georgia.

Talk to you again SOON!

SleepyCat.

[MattW]

Always glad to see your info Sleepycat! I think that the segment between Scottdale and Lithonia isn't APB at all, especially not if your brother saw a Westbound (RR Northbound) train and SE Stone Mountain came up to Approach Limited after it passed. In APB territory like the rest of the Georgia Sub, the signals in the opposing direction remain red even after the train clears them. Now I could see APB being modified to allow this for trains entering from unsignaled sidings such as the Stone Mountain siding in this particular example, but no idea if that's the case.

As for news from me, it looks like CSX has activated the approach-lighting on all the signals. I went Conyers to Scottdale today and in the Atlanta Terminal Sub, only Scottdale was lit. This was expected, but still I missed seeing that oh so pretty advance approach lit up like the last time I went by!

[MattW]

It looks like CSX is running more trains over this line, but I don't know if that's due to the signal upgrades here, or trouble on the normal Waycross-Atlanta route. Two weeks ago, I caught K470, Tampa-Avon, IN Northbound holding the main at Scottdale, and today I caught G800 (Ohio-Brunswick, GA) Southbound. I imagine these trains usually go via Manchester, but they're being rerouted on the ex-Georgia line. If there isn't an issue and they're just using this line to help spread the traffic around, then I'm glad to see that as it means rail service will continue for years more!

[SleepyCat]

I see no problem about the line being used for years to come MattW. In fact if anything, PTC will allow CSX greater flexibility operating trains on the Georgia line. No matter what the CSX cargo shipping to seaport in Savannah is always there. There are two lines from Atlanta owned and used by CSX and Norfolk Southern, terminating in Savannah that are very similar; CSX Atlanta to Savannah via Augusta and Norfolk Southern to Savannah via Macon through the Jackson ‘H’ and Griffin ’S’ Lines. Both the CSX and NS ‘S’ use Track Warrant. CSX utilizes ABS to increase track capacity and train speed functioning as a medium density line and as a diverter line. The Norfolk Southern ‘S’ route is strictly Track Warrant, a secondary line serving relief for the primary ‘H’ line going through Stockbridge.

I’m very sure that until implementation of PTC the segment between Scottsdale and Redan was APB. When the CSX crewman explained to me back in the 1990’s they were installing automated interlockings at Lithonia, Social Circle and Buckhead, he said the line is being upgraded from ABS to ‘poor man’s CTC’ or APB. So when you think about it having APB as a primary control and PTC as an overlay could present interoperability conflicts. Here is my reasoning;

Since the purpose of APB is to prevent collisions in bi-directional traffic on a single track line with manual control signals and sidings, having PTC makes APB at least appear redundant (TWC overlay with ABS overlay with PTC). PTC stops a train from head on collisions among other things, which is what APB supplementing TWC is supposed to do. With the PTC control feature I don’t really see the need for APB. PTC as an overlay for CTC makes more sense because CTC depends singularly on a dispatcher remotely controlling turnouts, signals, electric locks, etc. Since only the Atlanta to Redan segment has been converted to PTC at the moment on the Georgia line, it stands for reason APB is used at least as far to Buckhead on I-20, where I believe the last automatic interlocking is before Augusta. After Buckhead I could not find another automated interlocking station in Union Point and as far as Camak Georgia about 44 miles out of Augusta, both that have long siding tracks suitable for train meets (yes, my brother and I traveled parallel to the line all the way from our home in Lithonia, 94 miles). At Greensboro, Union Point there is standard ABS. The signals at Rutledge and Union Point, both ‘flower pot’ design, are constantly lit and APB as identified by the lack of faceplate. I’ve attached a picture of the Rutledge at night time as well as the meeting tracks in Union Point and Camak.

I’ve watched APB in action between Conyers and Lithonia; a train following another in the same direction will cause signals to respond in normal ABS fashion. However trains in opposing directions will cause signals to tumble down to their most restrictive element. I had seen a westbound train waiting on the main track in Lithonia while just a few minutes behind it in Conyers another westbound train approaching the absolute signal located adjacent to the Bio-Labs plant had turned yellow. However once a train is headed eastbound on the main Lithonia track, and the nightly Conyers local has finished switching duties behind Wal-Mart in Conyers the absolute located at Bio-Labs is red in both directions as well as the ones located at Sigman Road and the automated interlocking station, east Lithonia.

SleepyCat.

[MattW]

So I know this is quite the old thread, but I had a revelation recently specific to the discussion at hand. The Approach Limited at the SE Stone Mountain is due to the speed limit change from 45 to 50 there at the SE Stone Mountain. If a train is going to have to stop at the 151 waiting for track to clear in Lithonia, there's no reason to throttle up from 45, so basically I believe this signal is for better/more efficient train handling. Of course, this is somewhat moot now that the Georgia Subdivision past YYG-149 has been nerfed to little more than a 25mph branch line