Based on the conclusion of the article above, safer practice for oil unit trains would be slower, which is what the FRA ordered.
C&NW, CA&E, MILW, CGW and IC fan
schlimm zugmann I'm nto saying the statistic is wrong, but the way it is presented may be misleading. It was pretty clear, but check the article linked above. The article is fairly short.
zugmann I'm nto saying the statistic is wrong, but the way it is presented may be misleading.
It was pretty clear, but check the article linked above. The article is fairly short.
What Shlimm said sounds right, I don't have stats right in front of me but having been onsite for a couple hundred derailments it has the right feel.
schlimm Based on the conclusion of the article above, safer practice for oil unit trains would be slower, which is what the FRA ordered.
But remember this: the refineries need so much oil a day. If we slow down the trains, are we not going to need more trains to keep the supply constant? If a refinery needs a loaded train a day, it doesn't matter if they are moving at 60mph or 30mph to the refinery, they will still need a loaded train a day.
So now you have (approx) 2x the number of loaded trains on the main, albeit slowly crawling to the refinery.
Now the question for those with a better undersatanding of probablility and statistics than me (just about anyone) - is that safer? Is it better to have more slower trains, or fewer faster trains?
I do now know.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
Randy StahlWhat Shlimm said sounds right, I don't have stats right in front of me but having been onsite for a couple hundred derailments it has the right feel.
I'm not saying it isn't right - just how useful is the stat?
How do you use that number?
The number cars derailed (and where in the train) when all movement is finished.
zugmannNow the question for those with a better undersatanding of probablility and statistics than me (just about anyone) - is that safer? Is it better to have more slower trains, or fewer faster trains?
Speed is a larger contributor than length. So I think you'd have to do a joint probability comparison. I think that is what the FRA did.
It's true that a 10 mph derailment is not as bad as a 40 mph derailment for obvious reasons. I'm not saying that oil trains should plod along at slow speeds but as Shlimm pointed out, that is exactly what the FRA is saying and doing and with real facts to back it up, certainly more facts than the woman advocating ECP !
schlimm The number cars derailed (and where in the train) when all movement is finished.
Okay, I can then see why the probability drops toward the end of the train. There would be fewer cars available to provide the combined kinetic energy to shove cars into the derailment.
zugmann schlimm Based on the conclusion of the article above, safer practice for oil unit trains would be slower, which is what the FRA ordered. But remember this: the refineries need so much oil a day. If we slow down the trains, are we not going to need more trains to keep the supply constant? If a refinery needs a loaded train a day, it doesn't matter if they are moving at 60mph or 30mph to the refinery, they will still need a loaded train a day. So now you have (approx) 2x the number of loaded trains on the main, albeit slowly crawling to the refinery. Now the question for those with a better undersatanding of probablility and statistics than me (just about anyone) - is that safer? Is it better to have more slower trains, or fewer faster trains? I do now know.
Thanks to Chris / CopCarSS for my avatar.
Randy Stahl It's true that a 10 mph derailment is not as bad as a 40 mph derailment for obvious reasons. I'm not saying that oil trains should plod along at slow speeds but as Shlimm pointed out, that is exactly what the FRA is saying and doing and with real facts to back it up, certainly more facts than the woman advocating ECP !
I'd be down with running 10mph oil trains.
Think of the OT? Ka-ching!
Murphy Siding I'll say C) More slower trains, but make them longer. The article also suggests that cars further back in the train are less likely to derail. Just add some more more further back there.
Hmm. I wonder how many refineries/loading racks could handle longer trains.
EuclidEuclid Nobody is advocating “perfect safety.” Of course that is impossible. What Secretary Foxx is advocating is “as safe as possible.”
Interesting parallel: (At least to me)
The public seems to take horendous aviation crashes, killing a hundred or more with great calm and some interest. "As safe a possible " is a reasonable standard. Why? Has the aviation industry sold this successfully to the media, government and the public? There're doesn't appear to be any demand for fail-safe aircraft that aren't completely demolished by impact with the ground or other aircraft. There are litterally thousands of aircraft in flight over crowded population centers every day. How has commercial aviation avoided restrictions on equipment and operations comparable to those being seriously discussed for oil trains?
Euclid Okay, I can then see why the probability drops toward the end of the train. There would be fewer cars available to provide the combined kinetic energy to shove cars into the derailment.
If you read the two reports Schlimm noted (and the second one is more informative than the first) you will find that the most common cause of a derailment is a track defect. If there is a track defect, then the front of the train will generally find it before the rear of the train will. The front of the train also finds collisions, misaligned switches and a lot of human error before the rear of the train does. In most cases a train is pulled therefore the in train forces are highest right behind the engines, meaning there is a higher probability of knuckle, drawbar or underframe failure near the head end. The sum of it all is the cars in the front of the train have a higher probability of being involved in a derailment then the cars on the rear.
Other tidbits pulled out of the reports, ECP are only marginally better than DPU, and ECP and conventional brakes are essentially the same in train induced emergencies. The only place the ECP performs better in emergency brake applications is in engineer induced emergencies (none of the oil train accidents so far were engineer induced emergencies, all were train induced emergency applications).
In the analysis of derailment causes, the group that would include "slack action" (train handling, non-brake) accounted for only about 2.5 % or so of derailments and derailed cars.
Dave H. Painted side goes up. My website : wnbranch.com
ramrodHow has commercial aviation avoided restrictions on equipment and operations comparable to those being seriously discussed for oil trains?
I would opine that people are willing to accept the risk with airplanes. They understand that you can't make them out of boilerplate, and that something in the air can fall to the ground. It is also pointed out that millions of miles are flown daily, and the accident rate is relatively low.
And there has been a lot of research into crashworthiness. Just like our automobiles are more survivable in a collision, so, too, are airplanes. They're even making parachutes for small aircraft. One wonders when they'll be out for the big boys.
Too - the airline industry has made quite the deal of how they've dealt with shortcomings that have been discovered. Today's airplanes tell the pilot (with a charming female voice) just about everything that's going on except for the amount of TP left in the johns.
When a problem with the rudder on one type of aircraft was discovered (after leading to several crashes), the entire fleet was repaired in short order. Sometimes, if such a problem is discovered, all of the affected aircraft are immediately grounded, until the problem is fixed (which doesn't usually take long).
Trains, however, are already on the ground. What can go wrong?
We've already heard the hue and cry about taking DOT111A tankers out of service. Applying the airline principle to them, they would all be out of service, and lined up for whatever modification was deemed necessary. So a few trains have to get cancelled...
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...
http://www.bbc.com/news/world-europe-32030270
Never too old to have a happy childhood!
zugmann Murphy Siding I'll say C) More slower trains, but make them longer. The article also suggests that cars further back in the train are less likely to derail. Just add some more more further back there. Hmm. I wonder how many refineries/loading racks could handle longer trains.
Murphy Siding zugmann Murphy Siding I'll say C) More slower trains, but make them longer. The article also suggests that cars further back in the train are less likely to derail. Just add some more more further back there. Hmm. I wonder how many refineries/loading racks could handle longer trains. OK. Upon further consideration, I've change my answer to D) Figure out how to slow the trains down out on the line, but speed them up everywhere else? Trains Magazine has published about 4 gazillion articles about how the railroads are always trying to figure out how to reduce the amount of time that trains sit still. Maybe they're on to something?
OK. Upon further consideration, I've change my answer to D) Figure out how to slow the trains down out on the line, but speed them up everywhere else? Trains Magazine has published about 4 gazillion articles about how the railroads are always trying to figure out how to reduce the amount of time that trains sit still. Maybe they're on to something?
Except for power, crew or space into a loading/unloading facility, oil trains don't sit - they just occupy track space - the slower they go, the longer they occupy their track space. As long as they occupy track space no other trains can occupy it.
Rats! Now I'm up to plan E) and I don't have a clue what that will be. I just hope that the oil industry and the railroad industry figure that out before the politicians apply their magic wand and *fix* the problem. What I do know, is that I'm more in favor of pumping oil in North America, with all the jobs and economic activity that it involves, rather than pumping oil in some unstable part of the world for our use.
Bloomberg article on sudden drop in number of oil trains. They may be overstating the reductions ?
http://www.bloomberg.com/news/articles/2015-03-27/north-american-railroads-caught-by-speed-of-crude-oil-collapse
dehusmanECP are only marginally better than DPU, and ECP and conventional brakes are essentially the same in train induced emergencies.
This is true because the car's braking force remains the same. Cars braking ratios are set by design to not slide wheels on empty cars. If you want loaded cars to stop faster, you have to increase the braking force proportional to the load.
Freight trains don't have long stopping distances because they are heavy. They have long stopping distance because the braking ration of loaded cars is so low.
Load proportional braking will stop loaded trains faster (and diminish kinetic energy faster). You can do this with or without ECP.
The reason freight cars don't have it already is the mechanical devices used to measure the load would on occasion stick in the loaded position and cause massive flat spots. The cars would then run loaded with the flat spots and tear up all sorts of things.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
The impact of those flat spots can and do cause rails to break under the train, and we all know what a broken rail can cause..... That bang, bang, bang, bang you hear is more than simply noise. The louder it is the heavier the impact (and the bigger the flat spot that causes it). I'm sure that is what Don is thinking of.
Incidentally, rail seems to be more vulnerable to breaking due to flat wheel impact in very cold weather. The CWR is already under tension. Pure speculation on my part but it may have been a factor in CN's recent string of derailments.
John
Having read several articles, I mentioned the potential impact of the collapse of oil prices on Bakken development and rail transport one or two months ago, but of course, the forces of denial of the obvious tend to be loud on here.
Load/ empty sensors and valves have been available and installed on some car types for quite a few years now. As Don said, however, their reliability - in the dirty, rough & tumble world of North American freight railroading - leaves something to be desired.
But the opposite problem - not of sliding the wheels, but of less braking force for a loaded car due to an inoperative sensor/ valve - was discussed in the report on the CN runaway of a locomotive and a single loaded [EDIT - deleted bulkhead] centre beam flat car on a steep grade near Lillooet, British Columbia a few years ago (29 June 2006). See "Sec. 1.14.4 - Sensor Plates and Empty/Load Devices" and related following sections at:
http://www.tsb.gc.ca/eng/rapports-reports/rail/2006/r06v0136/r06v0136.asp
- Paul North.
Better yet, see Sec. 1.14.2 - Net Braking Ratios ("NBR"), from which the following quote was taken (emphasis added - PDN):
"At the 2004 Technical Conference of the AAR Air Brake Association, a paper titled Increasing Train Safety and Capacity with a Better Brake Shoe stated:
Car weights have increased from 220,000 pounds to 286,000 pounds and are headed higher . . . S-401 recommends a loaded car NBR of between 12% and 12.5%. The changes were made to provide improved grade braking. Some railways, notably CN and CP, have built 263,000 pound coal and grain cars at well above the minimum NBR specification for many years to ensure adequate braking performance on steep grades in unit train service."
So it appears that significantly better braking performance is possible.
Even 12 - 12.5% is only about half of what could be achieved on reasonably good rail conditions - 25% is a common (slightly high) figure to base the tractive effort of locomotives without anti-slip control, etc. But this higher figure would not be achievable even in an emergency braking scenario - the brake cylinder size, pressure, lever arrangement, brake shoe composition, etc. are set up to keep the ratio at the lower figures. Perhaps that ought to be adjusted as well - many flat wheels are cheaper than a wreck.
By the way, I like Euclid's idea for 'dial-a-brake' (my term) to instantly adjust the braking ratio in an ECP system on a limited group of cars to account for the empty/ load issue, without the unreliable Rube Goldberg arrangement of the load sensors and plates, etc.
Paul_D_North_JrBy the way, I like Euclid's idea for 'dial-a-brake' (my term) to instantly adjust the braking ratio in an ECP system on a limited group of cars to account for the empty/ load issue, without the unreliable Rube Goldberg arrangement of the load sensors and plates, etc.
Ah, yes. Subway cars have been doing this for 60 years. Mostly to keep the cars level at the platforms so the gees would not need to jump up or down according to the load in the car. Clearly a suspension device.
On a "smart car" such as envisioned by the LION, this could be set to control the braking. Heck no special work is required, just a laser across the springs will tell the story of who much brake is needed for this load.
ROAR
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
BroadwayLion On a "smart car" such as envisioned by the LION, this could be set to control the braking. Heck no special work is required, just a laser across the springs will tell the story of who much brake is needed for this load.
Ah it all sounds so simple.
If it has a laser that means there has to be power source. To have a power source that means a wire with two connections in it. A laser is an optical device. That means the lens of the laser has to be kept clean and whatever the light is hitting has to be kept clean. A laser is a pinpoint light so alignment is importnat. Maintaining alignment on an unsprung part of the car is going to be a challenge. It will be directly subject to any shocks of impacts between the wheel and the track. If the laser is to be on a sprung part of the truck it has to be attached to the bolster.
Its not impossible, but it looks like a real maintenance challenge. One rainstorm could render it ineffective if dust and dirt get on the laser lens or the target the laser is aiming at.
So that we may properly appreciate the effects of ECP and Net Braking Ratios on train stopping distances, let's look at a few numbers (as most of you know I am wont to do - but I'll spare you the lengthy derivations):
Consider a train moving at a Velocity of 40 MPH = 58.8 ft./ second - call it 60 ft./ second for simplicity, with tank cars at an average length of 60 ft.
The stopping distance - ignoring reaction/ response and propagation time, which would be nil for an electronic system - and assuming the deceleration/ braking rate is essentially constant - is from basic physics:
Stopping Distance = 1/2 x Braking Rate (in ft. / second, squared) x Time to Stop (in seconds), squared
Knowing that the Time to Stop = Velocity / Braking Rate, and making that substitution, we get:
Stopping Distance = 1/2 x Velocity (in ft. / second), squared / Braking Rate (in ft. / second, squared)
Inserting the Velocity of 60 ft./ second, we start with:
Stopping Distance = 1/2 x 60 ft./ second x 60 ft./ second / Braking Rate (in ft. / second, squared)
Doing the multiplication, we get:
Stopping Distance = 1,800 ft., squared / second, squared / Braking Rate (in ft. / second, squared)
Simplifying the units, we get:
Stopping Distance = 1,800 ft. / Braking Rate (in ft. / second, squared)
Since Braking Rate = Net Braking Ratio x Acceleration due to Gravity ("G") = 32.2 ft./ second, squared, the number crunching will now be fairly simple. So:
For an AAR S-401 2004 Minimum Braking Ratio (from the TSB report) of 11%, the Braking Rate = 11% x 32.2 = 3.54 ft. / second, squared (about 2.4 MPH per second, for those who prefer or are accustomed to seeing it expressed that way)
Substituting, we get:
11% Stopping Distance = 1,800 ft. / 3.54 = 508 ft. = 8.5 car-lengths
For the Maximum Braking Ratio of 14% = 4.51 ft. / second, squared (3.07 MPH/ sec.),
14% Stopping Distance = 1,800 ft. / 4.51 = 399 ft. = 6.7 car-lengths
For the former standard (1999 - 2004) of 8.5% = 2.74 ft. / second, squared (1.9 MPH/ sec.),
8.5% Stopping Distance = 1,800 ft. / 2.74 = 658 ft. = 11 car-lengths
If we can achieve a Net Braking Ratio of 25% with ECP brakes = 8.05 ft. / second, squared (5.5 MPH/ sec.), then -
25% Stopping Distance = 1,800 ft. / 8.05 = 224 ft. = 3.7 car-lengths
So we could potentially go from pile-ups of what seem to be 10 - 20 cars - which are consistent with the stopping distances for the old 8.5% and current 11% Net Braking Ratios - to as low as 4 cars with a more powerful and faster-acting braking system.
It would be interesting to compare this theoretical calculation with the performance of the subway cars that Broadway Lion refers to.
If someone wants to write a R&D proposal to the FRA for this, I suppose I could be available for a modest fee . . .
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