This summer, near Orin Junction(?) south of the Powder River Basin in Wyoming, and last weekend, just north of Omaha, Nebraska, I saw UP trains on what appeared to be really close headways. The Wyoming coal trains seemed to be spaced only about 5 to 10 minutes apart. We saw 4 in about 20 miles. The Omaha trains, (actually in Iowa), were spaced about 10 to 15 minutes apart.
On a busy, fluid rail line, how close can the dispatcher run trains?
Thanks to Chris / CopCarSS for my avatar.
Well 15 miles apart sounds reasonable. If speeds were 60 mph (just a guess) and trains were 15 miles apart, and signals were 2-3 miles apart then then that should be pleanty safe (at least enough for a FY-Y-R and then some). On the other hand 4 in 20 miles is a bit dense, they were probably running on yellows and/or flashing yellows.
* just a guess though as I am not familiar with the signaling out that way.
Murphy Siding This summer, near Orin Junction(?) south of the Powder River Basin in Wyoming, and last weekend, just north of Omaha, Nebraska, I saw UP trains on what appeared to be really close headways. The Wyoming coal trains seemed to be spaced only about 5 to 10 minutes apart. We saw 4 in about 20 miles. The Omaha trains, (actually in Iowa), were spaced about 10 to 15 minutes apart. On a busy, fluid rail line, how close can the dispatcher run trains?
Minimum headway is a function of block length, which in turn is a function of:braking curves, which in turn are a mathematical formula unique to each railway signal department, which has at its independent values:
In general in North American practice, trains are not significantly longer than the average block length. There are many blocks shorter than a long train, of course.
With following trains, and CTC multiple main-track or ABS Rule 251 double-track territory, the limit on the dispatcher's workload occurs at terminals, where trains bunch up to change crews or enter yards. He can only call trains so fast. Out on the line, however, minimum headways are determined not by the dispatcher but by the automatic block system. The dispatcher can stack in routes all day long and the signal system will space the trains out on its own. If the trains take their aspects promptly, they can run at their minimum safe headways all day long.
You're probably looking for hard and fast numbers, so if we want all of our trains to run on nothing but green aspects in a four-aspect system (R, Y, FY, G), and our railroad is perfectly flat, and we have a maximum 153 TPOB, our block length cannot be less than ~ 4,000 feet (30 mph to 0 mph minimum distance between block signals) and the minimum headway is thus 12,000 feet. At 60 mph, or 5280 per minute, we have approximately 2.5 minute headways. But in the real world on a perfectly flat railroad, we will more likely have 8,000 foot blocks or 25,000 feet headways, because no one in their right mind is going to signal a railway these days with 4,000-foot blocks mile after mile. That equates to ~ 5 minutes at 60 mph.
RWM
4 in 20 miles. If driving toward trains, then there is a deviation in timing. Standing still, four in 20 would be 5 minutes apart. Driving against the current of traffic would yield more time between trains depending on your speed (a variable) and more distance. ie. if you are traveling against the current of traffic at a steady 60 mph and the traffic coming at you is doing the same steady 60, and you meet a train every 5 minutes, then the actual time between trains is 10 minutes. .
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henry6 4 in 20 miles. If driving toward trains, then there is a deviation in timing. Standing still, four in 20 would be 5 minutes apart. Driving against the current of traffic would yield more time between trains depending on your speed (a variable) and more distance. ie. if you are traveling against the current of traffic at a steady 60 mph and the traffic coming at you is doing the same steady 60, and you meet a train every 5 minutes, then the actual time between trains is 10 minutes. .
Murphy Siding I had been doing those story problems from hell at the time: "If loaded coal trains are heading east at about 50 m.p.h., and a family on vacation is heading west at about 60 m.p.h. through an incredibly heavy thunderstorm ......." It was raining so hard, I couldn't tell if it was single or double track at that point.
I had been doing those story problems from hell at the time: "If loaded coal trains are heading east at about 50 m.p.h., and a family on vacation is heading west at about 60 m.p.h. through an incredibly heavy thunderstorm ......." It was raining so hard, I couldn't tell if it was single or double track at that point.
And school teachers everywhere are laughing, remembering untold generations of students in math class saying, "Why do I need to learn this? I'll never need it after I get out of school!"
"...and you see", as Albert would say, "it's all relative."
"We have met the enemy and he is us." Pogo Possum "We have met the anemone... and he is Russ." Bucky Katt "Prediction is very difficult, especially if it's about the future." Niels Bohr, Nobel laureate in physics
The train was 1/2 mile from the road crossing and traveling at 60 MPH.
From a distance of 1/3 mile the auto was proceeding, at a right angle, toward the crossing at 50 MPH.
Question: Did the driver get across? Yes, a white marble cross with his dates of birth and death on it.
RWM:
[Railway Man"]You're probably looking for hard and fast numbers, so if we want all of our trains to run on nothing but green aspects in a four-aspect system (R, Y, FY, G), and our railroad is perfectly flat, and we have a maximum 153 TPOB, our block length cannot be less than ~ 4,000 feet (30 mph to 0 mph minimum distance between block signals) and the minimum headway is thus 12,000 feet. At 60 mph, or 5280 per minute, we have approximately 2.5 minute headways. But in the real world on a perfectly flat railroad, we will more likely have 8,000 foot blocks or 25,000 feet headways, because no one in their right mind is going to signal a railway these days with 4,000-foot blocks mile after mile. That equates to ~ 5 minutes at 60 mph.
RWM: Your post brings up a question that I"ve been waiting for for the right thread.
CSX's A&WP subdivision had a signal upgrade about 16 years ago eliminating the code line but staying mostly automatic block. Signal blocks were lengthened to about an 2.4 mile or less length with one exception listed below. In 2007-08 CTC was completed from MP 6.3 in East Point to LaGrange, Ga. with the installation of two additional sidings being installed that were approximately 2.4 miles long. (Greentop and Moreland). These sidings were installed for the BNSF Haulage trains from the west coast to Fairburn (ATL) which number three or four a day each way being approximately 8000 - 10000 ft long. But here is the problem. From south to north there is an intermediate signal at MP 63.67; approach signal at MP 61.23; south end of Hogansville siding at MP 59.6; North end Hogansville 57.3; Then a cabin only (no signals and cabin identical to all other intermediate signal cabins) at MP 55.1; an approach signal for south bounds at MP 53.1; an advanced approach signal for Moreland at MP 50.4 (can show FY); approach signal for Moreland at MP 47.0 and south end Moreland signal at MP MP44.37.
Now CSX is famous for fleeting their trains (as many a six in one direction). So when the first northbound passes through no problem. When the 1st end passes the North end of Hogansville a restricting aspec (lunar) is displayed and remains until the rear end passes signal at MP 53.1 then Hogansville displays appproach (Y) and when end passes MP50.4 clear (G) displayed. All the following trains then have to approach the north end of Hogansville slowly (usually 20 MPH) waiting for at least an approach signal but preferably the clear signal. Naturally this stacks all the trains up and can really slow those BNSF intermodals if they are not leading the fleeting. Remember the line from LaGrange to Atlanta carries both Montgomery and Birmingham traffic. (LaGrange - Birmingham is continuning to receive lengthened and more sidings to handle its traffic). This problem also applies to the southbound trains except they stack up from Hogansville to Moreland and North.
A couple of other items that may apply. The whole subdivision has a 50 MPH limit except intermodal trains. I've been told the ruling grade is from Hogansville northbound to MP 51.9.(Signal 53.1 has a Grade plackard none at Hogansville) All trains both north and south have ample power with the exception of some ballast trains as I've paced many of them at 50MPH both ways including loaded coal trains. I have not observed any other advanced approach (F/Y) on this line. Why would this one block segment be 4.2 miles long and not the 2 - 2.4 miles on all other blocks on this subdivision? It certainly can slow the BNSF intermodals when fleeting occurs.
blue streak 1RWM: Your post brings up a question that I"ve been waiting for for the right thread. CSX's A&WP subdivision had a signal upgrade about 16 years ago .... (cut for space)
CSX's A&WP subdivision had a signal upgrade about 16 years ago .... (cut for space)
None of this stuff is that straightforward, and there are lots of unusual things that happen depending on how new signal installations are interfaced with older signal installations.
If someone would send me current pdfs of the track charts for this section and the appropriate pages from the Special Instructions showing the signal aspects and indications, I might be able to figure out what's going on. But I mostly likely would need to see the signal line maps and aspect charts, too. Anyone have them they can email me?
RWM: May be able but will take awhile to get track charts but additional information is: The old code line system had spacing of about 1.1 miles between signals and the ABS upgrade 18 years ago had the average 2.2 miles( took about 2 mos from MP 25.8 to MP 69.1). That was when the 4.4 mile spacing occured from Hogansville to MP 53.1. The CTC upgrade took about 6 Months from the same points with all of it installed as RCL (Radio Control Line). Note signal locations essentially same locations as 18 years ago.
Railway Man Minimum headway is a function of block length, which in turn is a function of:braking curves, which in turn are a mathematical formula unique to each railway signal department, which has at its independent values: Average grades ascending or descending between block limits in the direction of travel Maximum tons per operative brake Maximum authorized speed on that particular line segment Number of available aspects in the aspect progression, which varies depending upon whether there is a diverging route involved anywhere in the aspect progression. Locations of interlockings and spacing between them, which throw into the aspect progression their own requirements for diverging routes. Various constants determined by each railway that account for maximum braking horsepower of a composite brake shoe on the tread of a freight-car wheel within a given speed regime, etc.The braking formula is used to determine the placement of wayside signals so that the heaviest possible train with the worst possible braking horsepower can never get an aspect that it cannot physically adhere to......................... ......................You're probably looking for hard and fast numbers, RWM
......................You're probably looking for hard and fast numbers,
Reading all the factors that go into determining the headway, what part will electronic(?) braking have on the system?
Murphy Siding' Wasn't actually looking for hard and fast numbers. I was just curious how UP could send trains so close together, and what it took to determine the distances. I was pretty impressed that they could run them so close together, especially the coal trains. Reading all the factors that go into determining the headway, what part will electronic(?) braking have on the system?
' Wasn't actually looking for hard and fast numbers. I was just curious how UP could send trains so close together, and what it took to determine the distances. I was pretty impressed that they could run them so close together, especially the coal trains.
I did the math for nothing?
Anyway, ECP might enable some small reduction in spacing, but probably not until the entire North American fleet is equipped, because block signal spacing is for the worst-braking train, not the best-braking train. PTC, on the other hand, might actually increase spacing because the braking algorithms have to assume worst-case-scenario, whereas a skilled engineer will usually know when his train will have a braking rate significantly worse than normal (e.g., packed snow on the brake shoes, wet leaves on the rail). We're in a lot of discussions about that now.
Back to your observation, if you think about trains departing a terminal into CTC territory with nothing out on the main for some distance away from the terminal. In general terms, the first train to leave will leave when it gets a signal indication more favorable than stop and stay. As soon as his EOT passes the next signal, the first signal will be able to give an indication more favorable than stop and stay, allowing the next train to depart, and so forth. The first train will accelerate away from the second, and the second from the third, because it will get more favorable aspects, assuming all have like HPT, and if nothing interferes after a short period the first train will be separated from the second by three blocks, the second from the third by three blocks, and so forth. If the first train comes up to a less-favorable aspect than proceed at maximum authorized track speed, the following trains will start to bunch up against it.
diningcar The train was 1/2 mile from the road crossing and traveling at 60 MPH. From a distance of 1/3 mile the auto was proceeding, at a right angle, toward the crossing at 50 MPH. Question: Did the driver get across? Yes, a white marble cross with his dates of birth and death on it.
It was a funny line, but just doing the math in my head, he makes it across with 6 seconds to spare.
Dakguy201 diningcar The train was 1/2 mile from the road crossing and traveling at 60 MPH. From a distance of 1/3 mile the auto was proceeding, at a right angle, toward the crossing at 50 MPH. Question: Did the driver get across? Yes, a white marble cross with his dates of birth and death on it. It was a funny line, but just doing the math in my head, he makes it across with 6 seconds to spare.
Not to pile on, but I got to the same conclusion, too. Details:
Obviously, the train gets there in 30 seconds (60 MPH = 1 mile per minute, so 1/2 mile = 1/2 minute = 30 seconds).
50 MPH = 50 MPH x 5,280 ft. per mile / 60 mins. per hour x 60 secs. per min. = 73.33 ft. sec.
1/3 mile = 5,280 / 3 = 1760 ft.
1,760 ft. / 73.33 ft./ sec. = 24.00 secs.
An easy way to make it work as intended is just to swap the speeds and distances, which are then probably more realistic and believable anyway - train at 50 MPH, car at 60 MPH. Then he runs into the side of about the 4th car behind the locomotives - about the trailing truck (see Mookie's " ? ? " thread about the car that went under the tank car . . . ) Details: Car gets there 6 secs. after the train went past at 73.33 ft. sec. = 440 ft.of the train has gone by when impact occurs. Say 3 locos at 70 ft. long = 210 ft., so there's 230 ft. of cars that have gone by. At 60 ft. per car, that's near the trailing end of the 4th car, about 10 ft. in from the end = about where the wheel truck is.
So we could change the answer to, "No, he hit the truck !", which would really mystify readers/ listeners unless they were as sick and twisted as we are . . .
Or, just change the answer slightly to: "Yes, he did get a cross - a white marble cross with his dates of birth and death on it." [addition emphasized - PDN] My sense of humor is somewhat leaden and lacking in subtlety, I suppose . . . .
- Paul North.
The train spacing is governed by the dispatching computer, and is displayed in front of the dispatcher. The system will allow trains to run at medium speed (30) on "approach" indications (yellow blocks), or at restricted speed (15 or 20, depending on the rules) on "stop and proceed" indications. The exception is at interlockings, where red is "stop and stay". The dispatcher monitors it all, and can override the computer if the situation requires. I'd be surprised if loaded coal trains are running at 60 MPH - they would create too much dust, lose product, and pound the rail silly. If the route is saturated with trains, they can only follow each other as closely as the TCS system allows. I would guess that coal trains five minutes apart, running 30 MPH, are actually about 2.5 miles apart. If everything is running smoothly (sometimes a big if), that's a safe distance - more than the needed braking distance, and at least a full block apart. In all likelihood, those trains were running at 30 MPH on approach blocks, and were about as close togetrher as is safely possible.
Yes, but what sane driver is going to maintain his 50mph velocity after looking at the locomotive bearing down on the crossing? Not me.
One other moot point. If the crossing has any kind of protection beyond cross-bucks the driver of said auto is due a ticket and may owe the railroad a new gate.
trackjackThe train spacing is governed by the dispatching computer, and is displayed in front of the dispatcher. The system will allow trains to run at medium speed (30) on "approach" indications (yellow blocks), or at restricted speed (15 or 20, depending on the rules) on "stop and proceed" indications. The exception is at interlockings, where red is "stop and stay". The dispatcher monitors it all, and can override the computer if the situation requires. I'd be surprised if loaded coal trains are running at 60 MPH - they would create too much dust, lose product, and pound the rail silly. If the route is saturated with trains, they can only follow each other as closely as the TCS system allows. I would guess that coal trains five minutes apart, running 30 MPH, are actually about 2.5 miles apart. If everything is running smoothly (sometimes a big if), that's a safe distance - more than the needed braking distance, and at least than a full block apart. In all likelihood, those trains were running at 30 MPH on approach blocks, and were about as close togetrher as is safely possible.
The train spacing is governed by the dispatching computer, and is displayed in front of the dispatcher. The system will allow trains to run at medium speed (30) on "approach" indications (yellow blocks), or at restricted speed (15 or 20, depending on the rules) on "stop and proceed" indications. The exception is at interlockings, where red is "stop and stay". The dispatcher monitors it all, and can override the computer if the situation requires. I'd be surprised if loaded coal trains are running at 60 MPH - they would create too much dust, lose product, and pound the rail silly. If the route is saturated with trains, they can only follow each other as closely as the TCS system allows. I would guess that coal trains five minutes apart, running 30 MPH, are actually about 2.5 miles apart. If everything is running smoothly (sometimes a big if), that's a safe distance - more than the needed braking distance, and at least than a full block apart. In all likelihood, those trains were running at 30 MPH on approach blocks, and were about as close togetrher as is safely possible.
UP and BNSF both permit unit coal (loads and empties) 50 mph. They attempt to hold that speed as much as possible on high-density main lines.
The dispatching computer does not govern train spacing. The field signal logic governs it. The dispatching computer is nothing but a means of relaying the dispatcher's requests to the field. The dispatcher selects route and priority only. Everything else is in the field.
All class 1 RR's UP/CSX/BNSF/NS run coal at 50 MPH, the FRA allows solid commodity trains to run at 60 MPH but RR's run at 50 MPH to save fuel and reduce emissions. The trains you saw running in Iowa were most likely all running on clears at about the same speed, crews know what train symbols can do what speed and adjust accordingly some will bring there train down to a crawl not to accept an approach signal so they do not have to continue at reduced speed thru the entire block, which is usally two miles, coal trains at 130 cars approximately, with three units are about 7000 feet long, so they should never exceed any non-interlocking to interlocking block.
There was one old timer from the EL...holy moley! I'm talking diesel era here!...who told me that right after the merger he and another engineer would leave Elmira, NY eastbound to Binghamton one following the other and running track speed on marker sight and radio chatter! Both supposedly knew the road well enough to know the speed limits and locations, etc. so that the one in the following train would apparently run yellow boards as green boards but would not pass a red board. Seat of the pants signalling that they say they got away with! The way he spoke the lead train went to Scranton on the Lackawanna from Binghamton while his train went on to Susquehanna on the Erie. He told me this story about 30 or so years ago of course. He is still around, retired.
Slightly off topic but I was involved (in a minor role) with the lawsuit against the railroads hauling coal from the Powder River. Somebody in the opposition figured out that if the trains ran as often as the RR wanted to, there would be some small towns that would be effectively cut in half - the grade crossings would be blocked by moving trains something like 40-45 min. out of every hour.
wjstix Slightly off topic but I was involved (in a minor role) with the lawsuit against the railroads hauling coal from the Powder River. Somebody in the opposition figured out that if the trains ran as often as the RR wanted to, there would be some small towns that would be effectively cut in half - the grade crossings would be blocked by moving trains something like 40-45 min. out of every hour.
Murphy Siding I'd have to challenge someone's methods there. At 7,000' long, going 50 m.p.h., I calculate a coal train would pass in 1.6 minutes. To be blocked for 40 minutes out of the hour, you would have to have 25 trains per hour(40 divided by 1.6). 25 trains x 24 hours =600 trains per day=31,200 trains per year. Am I doing the math right? And besides, who could argue with any railroad able to run 31,200 trains per year down a line?
Math is OK except for the last - it appears you multiplied the 600 trains per day only by 52 weeks per year = 31,200 trains.
Instead: 600 trains / day x 365 days / yr. =
219,000 trains per year = roughly NYC subway density, I suppose !
But don't forget that the crossing gates will go down at least 30 seconds before the train gets there, and will take a few seconds to go back up afterwards. So it's more like 1.6 + 0.5 + 0.1 = 2.2 mins. per train. So 40 mins. blocked crossings would be about 18 trains per hour - or only about 157,680 trains per year !!!
But if you have a double track main wouldn't trains running "side by side" and/or trains running in the opposite direction change the calculations so that the crossing could actually be unusable by auto traffic 40 or more minutes per hour?
Sullyman626 All class 1 RR's UP/CSX/BNSF/NS run coal at 50 MPH, the FRA allows solid commodity trains to run at 60 MPH but RR's run at 50 MPH to save fuel and reduce emissions. The trains you saw running in Iowa were most likely all running on clears at about the same speed, crews know what train symbols can do what speed and adjust accordingly some will bring there train down to a crawl not to accept an approach signal so they do not have to continue at reduced speed thru the entire block, which is usally two miles, coal trains at 130 cars approximately, with three units are about 7000 feet long, so they should never exceed any non-interlocking to interlocking block.
If the trains in Iowa were doing anything close to track speed, they were definitely running on clear signals. Automatic Train Control begins at the north end of Council Bluffs. Except for a couple of signals near Missouri Valley, even an Advance Approach (flashing yellow) will cause them to reduce to Restricted Speed to avoid a penalty brake application.
The signals between Council Bluffs and Missouri Valley were recently (within the last year) changed. The changes were block lengths and the addition of the Advance Approach indication. Before the blocks were longer and only displayed G - Y - R. Now they can display G - FY - Y - R. To maintain maximum speed trains have to be about 5 to 6 miles apart.
Jeff
henry6 But if you have a double track main wouldn't trains running "side by side" and/or trains running in the opposite direction change the calculations so that the crossing could actually be unusable by auto traffic 40 or more minutes per hour?
jeffhergert Sullyman626 All class 1 RR's UP/CSX/BNSF/NS run coal at 50 MPH, the FRA allows solid commodity trains to run at 60 MPH but RR's run at 50 MPH to save fuel and reduce emissions. The trains you saw running in Iowa were most likely all running on clears at about the same speed, crews know what train symbols can do what speed and adjust accordingly some will bring there train down to a crawl not to accept an approach signal so they do not have to continue at reduced speed thru the entire block, which is usally two miles, coal trains at 130 cars approximately, with three units are about 7000 feet long, so they should never exceed any non-interlocking to interlocking block. If the trains in Iowa were doing anything close to track speed, they were definitely running on clear signals. Automatic Train Control begins at the north end of Council Bluffs. Except for a couple of signals near Missouri Valley, even an Advance Approach (flashing yellow) will cause them to reduce to Restricted Speed to avoid a penalty brake application. The signals between Council Bluffs and Missouri Valley were recently (within the last year) changed. The changes were block lengths and the addition of the Advance Approach indication. Before the blocks were longer and only displayed G - Y - R. Now they can display G - FY - Y - R. To maintain maximum speed trains have to be about 5 to 6 miles apart. Jeff
Aha - now we've got some real information !
Jeff - What is the rule/ speed associated with the Advance Approach (Flashing Yellow) indication in this territory ? As compared with Approach ("hard" Yellow) ?
Now I'm wondering what speed would be optimum to maximize the number of such trains through a terrirtory or past a point in a given time, say 1 hour ? As a comparison, early in my engineering education we looked at the speed vs. volume data for cars in the tunnels under the Hudson River into NYC. As I recall, the optimum speed for max. throughput was - somewhat surprisingly - around 30 MPH. Not 60 MPH - instead, everyone went slower, but the closing up of the spacing between the cars more than made up for that.
Thanks for the detailed information !
The rules for Advance Approach and Approach don't really change. What causes trains to slow down in ATC is that it uses a two aspect cab signal either clear or restricting. Most places in ATC when you go past an Advance Approach, the cab signal changes to a restricting. ATC allows you only so much time to get down to restricted speed before it initiates a penalty brake application. Once down to restricted speed the equipment will not allow speed to rise over 23 mph under a restricting cab signal. If it does, the ATC will initiate a penalty brake application. So for everyone to be doing track speed or close to it, everyone has to be on clear signals. It should be noted that the Restricted Speed rule's limit of 20 mph or less (sometimes a lot less) still applies. The 23 mph limit is what the equipment is set to.
My last trip out there we were doing about 40 going through that area. When we entered a block where we would see the next signal, it would light up as a FY and change to G when we were about half way through the block. Maximum time table speed, if your train isn't restricted by some condition, is 60 MPH between Council Bluffs and Mo Valley.
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