The "After PTC" article in the Feb Trains is interesting. But ...
It states that moving blocks would be very beneficial to unit coal trains, whereas intermodal trains do just fine with the current fixed-block system.
Why the heck would that be? Why does the type of freight matter?
Is it because a long coal train is slower and more prone to delays, while an intermodal train's pace is more predictable? That's all I can think of; and I'm not sure what I just said about those two train types is even true.
Still in training.
Lithonia OperatorThe "After PTC" article in the Feb Trains is interesting. But ... It states that moving blocks would be very beneficial to unit coal trains, whereas intermodal trains do just fine with the current fixed-block system. Why the heck would that be? Why does the type of freight matter? Is it because a long coal train is slower and more prone to delays, while an intermodal train's pace is more predictable? That's all I can think of; and I'm not sure what I just said about those two train types is even true.
Intermodals are already given preference in Dispatching - ie. getting lesser priority trains in the clear to allow the Priority trains to be operating on clear signals. Lower priority trains, in many case are operating on less than clear signal indication. Rolling 'blocks' would give the lower priority trains to operate more frequently on 'clear blocks'. At least that is the theory. In actual practice??????
Never too old to have a happy childhood!
It does have the ring of a solution in search of a problem.
One thing that gets overlooked by many in the operation trains in signalled territory.
When a train is Overtaken by a higher priority train, it will not leave the siding immediately after the priority train has passed - to do so would have the train leaving the siding operating under the requirements of a Restricted Proceed signal indication - operating at 20 MPH or less and WITHIN 1/2 the range of vision looking out for a train or other obstruction ahead until they get a more permissive signal indication at the next signal.
Normally the overtaken train will wait until they get some form of a Approach indication, that permits them to operate at 1/2 the maximum authorized speed not exceeing 30 MPH and being prepared to stop at the next signal. The Approach form of signal indication tells the overtaken train there is NO TRAIN or obstruction between it and the next signal - a much 'easier' operating condition.
To get a Clear indication there must be at least TWO (and in some systems more) signal blocks between the two trains. Once upon a time signals were spaced at a nominal mile or so; when the carriers started operating larger trains they began spacing signals at a nominal two mile distance, in the 21st Century the signal spacing has been extended to a nominal three miles between signals - the spacing is to allow for nominal, non-emergency, braking distance. PTC enforced braking distances may be longer.
The higher priority train is moving north and lower priority train is heading south. Why hold the lower priority train once the rear of ther higher priority train has cleared the switch and is proceeding north?
caldreamerThe higher priority train is moving north and lower priority train is heading south. Why hold the lower priority train once the rear of ther higher priority train has cleared the switch and is proceeding north?
Trains being OVERTAKEN are moving in the same direction. Trains that MEET are moving in opposite directions.
caldreamerThe higher priority train is moving north and lower priority train is heading south. Why hold the lower priority train once the rear of the higher priority train has cleared the switch and is proceeding north?
What Balt was describing is a different situation entirely, looking at the other end of the siding with both trains proceeding the same way. In an absolute-block system, the lower-priority train would have to remain in clear until the higher-priority train completely cleared the block past the end of the siding -- only at that point could it start more than a little acceleration. CBTC can be arranged to gauge the actual separation based on speed and acceleration as well as default physical distance, so what happens is that the switch traverses and the lower-priority train can proceed with 'as much dispatch as it can muster' just as if it were entering a clear block, until the speed of the lower and higher priority trains become equal.
In practice there would be some leeway allowed for emergency braking or catastrophic derailment of the 'high-priority' train in the example, more of course if the 'continuous' were in some sense functionally intermittent in speed tracking, or some of the NAJPTC engineers left the food-service industry for another try at train control and forgot about tracking the back end speed as well as the front.
But for slowly-accelerating coal trains trying to save fuel, being able to start rolling up to hopefully-sustainable track speed early is a meaningful time saver. And once that train is up to track speed, its inertia will likely help it on even an undulating profile to maintain 'one-speed' reasonably, so following trains will be less 'stabbed' by the required wait to clear the absolute block behind an accelerating coal train if they know where it is and how it is changing speed...
I was not impressed with the article. There were things that the author didn't get quite right in current PTC operation and some of the subsystems that we have. I'd have to get out the article for specifics.
The theory is that rolling/moving blocks allow trains to run on closer headways. That the point of where authority to move ends will be at (or more likely close behind) the end of the train ahead, instead of a fixed signal boundary point. The moving boundary is going going to be continuously calculated, including the changing braking distance to the end point. I'm not sure that going to moving rather than fixed point boundaries will make that big of difference. I think it will cost more to get that capability than possible savings from closer headways will actually save them.
Jeff
jeffhergert I'm not sure that going to moving rather than fixed point boundaries will make that big of difference.
I would opine that the place moving blocks will make a difference is on heavily used lines, where the reduced headway between trains will increase capacity.
For simplicity's sake, moving blocks would be a lot like driving your car - you hopefully leave a suitable space between you and the car ahead. As the speed goes up, so does the distance.
OTOH, if you are the only car in sight, your speed is governed by the posted speed limit and the abilities of your vehicle.
If you watch the various train cams around the country, you'll rarely see two trains on short headway. More often, they are an hour and more apart in any given direction. On a single track line, sans fleeting, rolling blocks would make virtually no difference.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
jeffhergert I was not impressed with the article. There were things that the author didn't get quite right in current PTC operation and some of the subsystems that we have.
I was not impressed with the article. There were things that the author didn't get quite right in current PTC operation and some of the subsystems that we have.
I enjoyed reading it. But there were several places were he stated X will mean Y. Or A will facilitate B. And my brain was like "well, you're saying that, but you're not showing me." So I had no idea how much of value was really there. Seemed like generalities/suppositions/predictions, but not a lot of clues to help someone like me to understand. Technical folks and current railroaders certainly would understand much more, but I'm not surprised to hear you say some of it was inaccurate.
Lithonia OperatorTechnical folks and current railroaders certainly would understand much more, but I'm not surprised to hear you say some of it was inaccurate.
Frustration, thy acronym is P - T - C.
It's been fun. But it isn't much fun anymore. Signing off for now.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.t fun any
greyhoundsIs this a fantasy? Oh, maybe. But with the communications tech we have today, and what we will develop in the future, who knows. It could happen.
I've done moves where you pull into a yard, a yard crew (which PSR/some style management doesn't like) - grabs onto your rear end set out - a utility (again, PSR and certain managers hate these) then moves and rehangs the marker and launches you out on your way.
Can even do the opposite for a pickup, or a modified way to do both.
Is a really quick process - road train takes a couple minute pause - and everything is on its way. It's amazing what (and how fast) you can do when you have a couple decent yard crews or utilities, and aren't relying on a 23,000 foot train to do all its work by itself.
All the electronic nannies and toys aren't going to replace a pair of boots on the ground. Period. That's the fantasy.
Is there any location on the North American rail system where moving blocks have been applied?
And Greyhounds, pickup in Ceder Rapids is simple with your concept
The through train from Omaha stops for a few minutes while the Ceder Rapids power has the switch benind the train thrown, couples on to the end of the train, with the former Fred de-activated and the one at the end of the Ceder Rapis block activated, and the Ceder Rapids power is the distributed power to Chicago.
zugmannI've done moves where you pull into a yard, a yard crew (which PSR/some style management doesn't like) - grabs onto your rear end set out - a utility (again, PSR and certain managers hate these) then moves and rehangs the marker and launches you out on your way.
So, how does this square with PTB?
tree68 zugmann I've done moves where you pull into a yard, a yard crew (which PSR/some style management doesn't like) - grabs onto your rear end set out - a utility (again, PSR and certain managers hate these) then moves and rehangs the marker and launches you out on your way. So, how does this square with PTB?
zugmann I've done moves where you pull into a yard, a yard crew (which PSR/some style management doesn't like) - grabs onto your rear end set out - a utility (again, PSR and certain managers hate these) then moves and rehangs the marker and launches you out on your way.
Fine if PTB has that reality accounted for in its software.
For decades B&O and later CSX had a scheduled train totally based on rear end setoff. Train 396 which in later CSX days became 296, originated in Flint MI with autoparts for the GM Assembly plants in Baltimore and Wilmington. Train operated with a caboose as the rear Wilmington car that was ahead of all the Baltimore cars, with the required caboose on the rear. Train arrived Bayview Yard in Baltimore for a crew change and set off - Bayview yard crew was sent out on the other Main to make the cut behind the Wilmington caboose and the train started to pull picking up the Conductor & Flagman on the Wilmington caboose on the fly as it passed BA Tower. Arrival to departure was normally 10 minutes. After cabooses were removed from trains the Bayview yard crew would make the cut behind the last Wilmington car and rehang the EOT from the rear of the Baltimore's.
Today neither Wilmington nor Baltimore have GM Assembly plants.
greyhounds OK, let’s presume that they eventually get this whole PTC/moving block thing working. There will be bugs and those bugs will need to be worked through. This happens with everything. While this is going on, many people will be complaining about “Change”. People don’t like two things; 1) Change and 2) The way things are now. So anyway, this whole moving block thing will require ultra-reliable communication between the lead train and the following train. If the lead train goes into emergency the following train needs to react immediately. So, if they get that worked out to 99.999% reliability, what can we do from there? Let’s talk about a set out at Cedar Rapids, IA. (My favorite “For Example” place.) Leave us just say that we’ve got a westbound out of Chicago for North Platte carrying a Cedar Rapids set out block. (OK, just to be clear, the word “Block” can have at least two meanings in railroading. As used above it means a section of track. As used in this paragraph forward it means a group of freight cars. Got that?) Current, and forever past, practice requires the entire train to stop. Then a “Ground Person” (gender neutral), or “Ground Persons” must manually uncouple the freight cars at the end of the block (group of cars). Leave the rest of the train sitting still (I hate that) and move forward past a switch. Then the switch must be changed so that a reverse movement will put the set-out block on a different track. Then the lead locomotives must reverse and shove the set-out block on to another track. Then the locomotives must be uncoupled by a ground person from the freight cars. Handbrakes must be set. Then the locomotives must move forward past the switch. The switch must again be changed so that the locomotives can back on to their train. A ground person must attend the recoupling and hook up the air hose. After the air brakes are found to be working properly the train may proceed on its journey to North Platte after spending a lot of time sitting still and blocking a track by not moving. Yetch! Now let’s do it with the “Power Stays with Block” concept introduced by Oltman. Add in the ultra-reliable communications. Also add “Helperlink” technology and software. So, the train is approaching Cedar Rapids from Chicago. There’s a DP unit toward the back of the train but in front of the Cedar Rapids block. It's got the Helperlink. (The Cedar Rapids set-out is on the rear of the train.) At a designated point, the Helperlink is cued remotely to separate the DP unit and block from the train. An EOT device on the preceding car immediately activates. A RC operator takes over, slows the set-out, a switch is thrown, and he/she brings the set-out on to its proper track. The rest of the train just keeps on rolling toward North Platte. It would save time and money as well as improve service to customers. A pick-up? Well I haven’t thought that through yet. Is this a fantasy? Oh, maybe. But with the communications tech we have today, and with what we will develop in the future, who knows. It could happen.
The most far-fetched, most unlikely thing to happen for the foreseeable future. "Ultra reliable communications."
They are going to have to start maintaining some of the simplest components better than they do.
Beverly (Cedar Rapids), where trains go to die. Mainly because most of the trains that need to work all show up at the same time. Even when they try to stagger call times at Boone to space trains.
Then a 10000 ft manifest picks up another 2000 ft solid block off the south side and another 2000 ft solid block off the north side. Might have to reposition engines to new DP configurations. Now you have a 14000 ft train that needs an initial terminal air test for the entire train. Better have a relief crew ready.
jeffhergert The most far-fetched, most unlikely thing to happen for the foreseeable future. "Ultra reliable communications." They are going to have to start maintaining some of the simplest components better than they do. Jeff
Even face to face we sometimes have a failure to communicate.
Well, now we've got this. Moving blocks might be closer than we realize.
BNSF receives patent for moving block system | Trains Magazine
The article says that moving blocks will make detection of broken rails easier.
Why would that be?
Lithonia OperatorThe article says that moving blocks will make detection of broken rails easier. Why would that be?
What it actually says is: “In addition, by partitioning the physical track blocks into multiple virtual track blocks, broken rail can be detected within an occupied physical track block.”
I'm a marketing guy, not an operating guy. But I'll take a stab at this. Corrections are more than welcome.
Currently, once a train passes the fixed signal at the beginning of a block it has no protection against a rail break, or anything else, occurring in the block while it's in the block. If there is a pull appart due to cold weather there is no way to warn the train since it has already passed the signal. Same thing with a switch. If a switch is changed after a train has passed the signal there is no way to warn the train. It has already passed the guarding signal.
With a moving block system the train is never past a signal. Since the block moves with the train anything happening ahead of the train can be communicated to the train. Granted, if the pull appart or switch allignment happens 200 feet ahead of the train this is not going to do much good. But if it's a mile or so ahead of the train effective action may well be possible.
Thanks, greyhounds. That makes sense. I very much appreciate the explanation.
That is indeed a great feature of moving blocks. I wonder how long it will be before we see a RR doing this. There will be an awful lot riding on the software. You can simulate things all day long, but at some point the railroad will have to try real-world tests. It's a little spooky. Once the GPS on my sailboat showed us as being in Portland (ME) harbor, when that was about 75 miles away. Apparently there was a magnetic disturbance where we were; another boat reported a similar anomaly. Another time, I created a waypoint in open water, and used it successfully to navigate. But the next time I was in the area, I wanted to use the waypoint, but couldn't find it; when I finally did, it was situated smack dab in the center of an island! Then, when I tried to move it or delete it, the GPS would not allow me to. So, although I have 198 other perfect waypoints, that one still sits on the island in Penobscot Bay. Point being, this stuff has glitches. Ask Boeing. Traditional lineside block signals have served well for a long time ...
greyhounds Lithonia Operator The article says that moving blocks will make detection of broken rails easier. Why would that be? What it actually says is: “In addition, by partitioning the physical track blocks into multiple virtual track blocks, broken rail can be detected within an occupied physical track block.” I'm a marketing guy, not an operating guy. But I'll take a stab at this. Corrections are more than welcome. Currently, once a train passes the fixed signal at the beginning of a block it has no protection against a rail break, or anything else, occurring in the block while it's in the block. If there is a pull appart due to cold weather there is no way to warn the train since it has already passed the signal. Same thing with a switch. If a switch is changed after a train has passed the signal there is no way to warn the train. It has already passed the guarding signal. With a moving block system the train is never past a signal. Since the block moves with the train anything happening ahead of the train can be communicated to the train. Granted, if the pull appart or switch allignment happens 200 feet ahead of the train this is not going to do much good. But if it's a mile or so ahead of the train effective action may well be possible.
Lithonia Operator The article says that moving blocks will make detection of broken rails easier. Why would that be?
Actually that makes no sense in the real world.
Train enters a track segment on a 'good' signal indication - train moves through the block and THE TRAIN breaks a rail underneath it as it passes. Subsequent trains that pass that formerly 'good' signal will now get a 'bad' signal.
My observation of the chain of events is based upon more than 20 years of first hand experience with the situations. Within the breadth of my territory, the first 'cold snap' of the Winter would generally generate between 6 and 12 broken rails or pulled apart rail joints over tha night. All were found 'AFTER' the passage of a train that had operated through the segment on 'good' signals.
You don't get 'good' signals into a track segment that has a broken rail or pulled apart rail joint. The vibration, impact or other stresses generated by the passage of a train is what brings about the ultimate failure.
Broken rails not found by physical inspection in signalled territory are found by the disruption of continuity in the rail.
It could be that in removing the need to sense trains that technologies that could better sense a broken rail could be used, as they would not need to compete with train sensing methods.
In the fiber optic world, testers can see exactly where splices have been made.
On further reflection, I totally get how GPS can be used to create a virtual, moving envelope of protection. And, if it works correctly, would be good at preventing train-train collisions.
But it seems like an independent, different technology would have to be used for detecting flaws, misaligned switches, etc. So I think maybe Larry is right. Maybe the current track circuitry could be modified/enhanced to deal better solely with track-condition issues.
Who thinks rails break on their own?
They break when they have defects that the stress of a train passing over them progress the defect to the point of actual breakage.
BaltACDWho thinks rails break on their own?
Most of the time the actual propagation of a break starts under traffic, but the actual failure -- the most obvious being severe cold tension breaks -- need not occur under a train. I think there is some incidence of bad welds, and some of the reported gauge-corner cracking damage became catastrophic with released shock in the beam of the rail, a bit like shattering tempered glass, not just at the point of impact damage.
The counterpart, sun kink, often doesn't need a train either, although it sure can get worse quickly as trains go over it. A combination of the two was the progressive kink on the ex-New Haven that was reported as steadily worsening by a couple of engineers and then produced either a derailment or sideswipe collision (I don't remember precisely which without checking) -- it was observed to get worse between trains as well as after each successive one.
Things that fall on rails, or that roll down roads or off bridges and hit rails, can cause damage too.
Lithonia OperatorBut it seems like an independent, different technology would have to be used for detecting flaws, misaligned switches, etc. So I think maybe Larry is right. Maybe the current track circuitry could be modified/enhanced to deal better solely with track-condition issues.
Sounds like cab signals ( a syytem that's been around 100 years+)
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