Longer Trains Cause More Derailments

[rdamon]

zugmann

 

 

rdamon

Talking to Airbus drivers they have the equivilent of Trip Optimizer. Climb, Cruise and Decent is all managed by the FMS (Flight Management System) computer. Do it yourself and get out line, expect a call from your union rep as the system will phone home. 

 

 

But when those systems crap out, or something huge and out of the ordinary pops up, then the company expects the pilots (or engineers) to have the skills of a 30-yr man that has been running every day.  

Can't. Have. It. Both. Ways.  

 

Agreed, but it will probably take a major incident to change behavior.  Look at the 737-MAX

[Euclid]

Cotton Belt MP104

As I went through this thread there were remarks that seemed to indicate some unkind remarks had been made. I was subject to that at one time and refused to post anything.

As I have said before if a participant is seemingly pretending to be an expert and is not, the method of dealing with the bulk of those comments can be ignored (I mentioned "extinction"). While it is true that the "dull and ignorant, they too have their story and should be heard to an extent. This is only civil behavior. But when the story and details are of extraordinary length one seems to not gain that much, even a flaw in information can be present (intentional or not) and that draws a reaction from those who know better....and the verbal fight is on.

Example: Posted by Euclid on Thursday, June 1, 2023 10:02 AM : In the comment there is a statement:   ““If you use air brakes, then all 840 car wheels of the train will have brake shoes pressing into them.”  Is that a not true statement?”  

 

Cotton Belt MP104: 

 

Even with the FRED which sends the “signal to brake” from rear as front is sending backward the signal to brake. This is a cascading operation and not immediate “all 840 wheels…have brake shoes pressing” ?  He Did Ask The Question is that not a true statement?  And I was wondering if I was right that the statement is not right.  Endmrw0621231426

 

I answered your question (highlighted in red), but you never responded, so just to clarify:

 

You were not right in your statement that seems to say you thought my statement about the number of brake shoes applying was not right.

 

You have quoted my original statement without its clarifying context which was, “It is only to distinguish the effects of air brakes compared to dynamic brakes.”

 

The point is the difference in applying air brakes which applies brake shoes on all 210 cars to slow them, versus applying only dynamic brakes that retard the wheels of only the leading two engines to slow 210 cars. 

[Overmod]

.

Reply was meant to go to a different thread.

[blue streak 1]

Instead of blaming longer trains let us measure derailments by car miles.  What is the derailment numbes by say million car miles?  Each derailment can go into a data base for its length.  Switching moves are probably the easiest types to define.

[BaltACD]

blue streak 1

Instead of blaming longer trains let us measure derailments by car miles.  What is the derailment numbes by say million car miles?  Each derailment can go into a data base for its length.  Switching moves are probably the easiest types to define.

Somewhere along the line the FRA keeps such statistics.

[NittanyLion]

zugmann

But when those systems crap out, or something huge and out of the ordinary pops up, then the company expects the pilots (or engineers) to have the skills of a 30-yr man that has been running every day.   Can't. Have. It. Both. Ways.  

They don't expect or demand that level of experience.  Day one experience should do it, but even that failed.  Air France 447 was lost because the pilot didn't know it was possible to stall an A330.  And the guy in the cockpit with the most experience never bothered to cross-check the physical controls until it was well past the point of no return.  

[Overmod]

NittanyLion

They don't expect or demand that level of experience.  Day one experience should do it, but even that failed.  Air France 447 was lost because the pilot didn't know it was possible to stall an A330.  And the guy in the cockpit with the most experience never bothered to cross-check the physical controls until it was well past the point of no return. 

That almost directly proves Zug's point, though.  No experienced pilot would ever say 'you can't stall an A330' -- the problem was that the person didn't think the aircraft was stalled when the fancy computers were telling him it wasn't.

And there's something well-established in cognitive science that's worse: when you have to constantly watch and second-guess an automatic control system, which may not be explaining its 'decisions', waiting hours and hours against the chance there might suddenly be 30 seconds of screaming terror.  (To say nothing about doing it on little sleep, outside circadian rhythm, after a night of sleep apnea with CPAP...)

That goes a long way toward establishing he's right when 'you can't have it both ways' -- just has been the case with automated highway design since the late Forties.

[diningcar]

To answer this: first define a longer train - 2000-4000-8000- 12000 feet. It becomes subjective and subject to biases which make it Imposible to satisfy all. 

[Euclid]

blue streak 1

Instead of blaming longer trains let us measure derailments by car miles.  What is the derailment numbes by say million car miles?  Each derailment can go into a data base for its length.  Switching moves are probably the easiest types to define.

 

The question I asked in the title of this thread does reflect a growing concern that the relative large increase in average freight train length is causing an increase in derailments.  The prospect has not been sufficiently investigated to determine whether the cause is train length in number of feet, or train length in number of cars.  Probably both play a role.

 

The presumed explanation is that the increased length of freight trains tends to cause higher in-train forces related to braking and power changes combined with slack action.  So the higher forces are primarily related to slack run-in and run-out causing spikes in the forces of buff (compression) and draft (tensile).  Too much buff force causes a train to buckle and jackknife.  Too much draft force “stringlines” a train on curves or pulls a train in two on straight track.   

 

Another possibly contributing factor is the preferred use of dynamic braking instead of using the automatic air brake.  Dynamic braking only applies brakes on the locomotive of a train.  In the days of 100-car trains with no DPU; and only head end engines in M.U.; dynamic braking was only a secondary type of braking, with the primary braking being done with the automatic air brakes. 

 

The reason was that automatic air braking spread the braking throughout the 100 cars of the train.  Whereas dynamic braking turned the multiple locomotives, which were only on the head end, into a giant anchor with the entire consist of 100 fee rolling cars shoving up against that anchor.  So unless the dynamic braking application was extremely limited, it would cause a significant risk of a derailment due to high buff force relatively nearer to the head end.  And if the dynamic braking was sufficiently limited to avoid such a derailment, it was simply not enough braking to safely control the train. 

 

However, in this era with DPU, that problem of excess buff force from dynamic braking has been greatly diminished because the DPU also distributes the dynamic braking.  But this distribution is still not thorough like it is with automatic air braking applying to each car in the train. 

 

Regarding the question of the number of derailments per car mile, the answer might be useful, but it is an entirely different issue, which is related to railcar construction.  It would not be an alternative to the question of the increasing number of derailments caused by growing train length raising in-train forces. 

 

The question that I asked in the original title is being researched for an answer by the FRA.  This cannot be easily done with test trains run to a point of derailment.  It has to be done with test trains run with sensors to record in-train forces.  The data from this could be used in the development of new computer test programs.  Then their results can be double-checked in more test trains.  Eventually, they will have a program that will accurately predict the in-train forces of any given train makekup, in any length of train. Then they will know what the limits are.