Because a) the work equipment didn't have permission to be on the track and didn't "shunt" the track circuit b) the train dispatcher failed to properly take the track out of service, thereby establishing exclusive track occupancy for the work equipment
PTC, in theory & if working properly, is independent of human error and able to automatically engage emergency train brakes to stop train before a physical obstacle is reached. My first question was if these trucks (called a “work train”???) were indeed high-rail equipped with bogie wheels to allow them to actually drive on the rails. Or were they simply in the “right of way” immediately next to rails? I just watched the B roll footage and I think I see small boogie wheeIs in the wreckage so it seems trucks were so equipped. I think this guy is saying they were indeed up on the rails of the actual track. I don’t know how PTC accounts for this type equipment? If the system relies on a human to enter equipment presence, either on, or in very close proximity to tracks, and thereby taking that section of track out of service, then it’s not really PTC, and subject to the exact same kind of human error that has caused countless wrecks in the past. I don’t know mechanical details of the bogie wheel system for this type equipment. S. Artesian’s previous reply above talks about “shunting” the track. If that means that anytime a bogie equipped machine or trucks are actually placed on the rails, the PTC system knows it & automatically recognizes it as a hazard, and shuts down that section of track & automatically stops any train that tries to enter that section of track, then that seems like how it should work. For machines working in very close proximity to, but not actually directly on, the rails I don’t know how PTC would recognize them? So maybe this still involves human action susceptible to error? If PTC is not automatically triggered by the presence of bogie wheel trucks being on the rails, then human error, either by dispatch / control, or possibly by the crews operating the trucks thinking they have permission to be on rails when they actually don’t, then human error is still possible. The concept of PTC in situations like this should eliminate the operator of the train from the system. If it were to simply rely on a train engineer seeing & reacting to a signal to stop, or hitting the emergency brake when he sees equipment on tracks, then it’s not PTC. Either way, this seems like a glaring failure, or design fault, in either a human, or mechanical system. I’ve spent countless hours watching NTSB dig into this type situation, be it planes, trains, automobiles, or bridges. I suspect they will figure this one out.
@@Bitterrootbackroads "PTC, in theory & if working properly, is independent of human error and able to automatically engage emergency train brakes" Nope, not exactly. PTC in theory and practice does not independently register the presence of on-track equipment, but relies on the "legacy" train control system to register the presence or "occupancy" of the track. On-track (maintenance) equipment, unlike locomotives and railroad rolling stock, does not always trigger that legacy system to register occupancy. Hence,, all railroad operating rules prohibit train movement into a section of track used by on-track equipment. Similarly, on-track equipment is prohibited from occupying the track without the permission of the train dispatcher, who, when granting permission, will apply devices that prevent the display of signals that might authorize following or opposing movements. Once the blocking devices are applied to signals that display "stop" PTC does its thing and sets a zero velocity target for trains approaching the signal. So...either the on-track equipment occupied the track without permission; or gave the dispatcher the wrong information on what track they were to use; or the employee in charge of the equipment reported "clear" to the dispatcher before the equipment was fully in the clear; or the train dispatcher failed to apply or improperly removed the blocking devices and wrongly displayed a signal authorizing movement of the train (either through forgetting, or miscommunication in a transfer between dispatchers). In my experience, all these things happened at one time or the other. It's horrible when it happens and PTC is not configured to overcome this vulnerability.
@@sartesian , Thanks! I have zero experience with NTSB, railroads or PTC, and only minimal with automated systems from an operators view. Even as I made my initial statement about how I thought PTC worked, I was realizing there could be situations like you explain. As soon as I questioned if these trucks were actually “on track”? And if so would they trigger PTC? I also realized that the mere presence of equipment in the immediate vicinity of tracks could present virtually an identical hazard, that no sensor could detect. Then I started thinking that there must be a human factor still involved? I’ll do some reading on how the Legacy system is supposed to prevent things like this. Can you recommend a resource or public forum where thinking people are discussing this? I looked on railroad.net but couldn’t find anything. Watching news anchors & reporters bungle their way through 2 minutes is worthless. The more I think about this, especially after reading your thoughts, it sounds much like the MCAS system failure that brought down 2 Boeing 737s. I’m not involved with aviation, but I went down that rabbit hole too! I worked in lumber manufacturing. Our automated logic systems were often less than perfect, but the result of their failures was mostly some bad product, or a big mess to clean up. Trying to get sales, engineers, electricians, operators, managers, & accountants together on something was an art.
Glad no one was killed, but the rescuers are heroes for saving every soul on that train and or ones who were involved! But I know that it’s not just me that wants to see that onboard outward facing video!
Typical government agency... leaving out critical facts in their media statement, Not one time did they mention that the train actually derailed from the impact.
Hi Eric, this is only an abstract of the statements that the NTSB has made - there was plenty of coverage before and after, of various quality and speculation by the media. NTSB is there not to make a "show' but to find out the cause of the mishap/accident, it is a very demanding investigative work without having all the speculators and lawyers around to disturb the investigation and get the viewers upset. I know, I have been there. Ciao, L
Good question if PTC was on why did the train enter the work Zone
Because a) the work equipment didn't have permission to be on the track and didn't "shunt" the track circuit b) the train dispatcher failed to properly take the track out of service, thereby establishing exclusive track occupancy for the work equipment
PTC, in theory & if working properly, is independent of human error and able to automatically engage emergency train brakes to stop train before a physical obstacle is reached. My first question was if these trucks (called a “work train”???) were indeed high-rail equipped with bogie wheels to allow them to actually drive on the rails. Or were they simply in the “right of way” immediately next to rails? I just watched the B roll footage and I think I see small boogie wheeIs in the wreckage so it seems trucks were so equipped. I think this guy is saying they were indeed up on the rails of the actual track. I don’t know how PTC accounts for this type equipment? If the system relies on a human to enter equipment presence, either on, or in very close proximity to tracks, and thereby taking that section of track out of service, then it’s not really PTC, and subject to the exact same kind of human error that has caused countless wrecks in the past. I don’t know mechanical details of the bogie wheel system for this type equipment. S. Artesian’s previous reply above talks about “shunting” the track. If that means that anytime a bogie equipped machine or trucks are actually placed on the rails, the PTC system knows it & automatically recognizes it as a hazard, and shuts down that section of track & automatically stops any train that tries to enter that section of track, then that seems like how it should work. For machines working in very close proximity to, but not actually directly on, the rails I don’t know how PTC would recognize them? So maybe this still involves human action susceptible to error? If PTC is not automatically triggered by the presence of bogie wheel trucks being on the rails, then human error, either by dispatch / control, or possibly by the crews operating the trucks thinking they have permission to be on rails when they actually don’t, then human error is still possible. The concept of PTC in situations like this should eliminate the operator of the train from the system. If it were to simply rely on a train engineer seeing & reacting to a signal to stop, or hitting the emergency brake when he sees equipment on tracks, then it’s not PTC.
Either way, this seems like a glaring failure, or design fault, in either a human, or mechanical system. I’ve spent countless hours watching NTSB dig into this type situation, be it planes, trains, automobiles, or bridges. I suspect they will figure this one out.
@@Bitterrootbackroads "PTC, in theory & if working properly, is independent of human error and able to automatically engage emergency train brakes"
Nope, not exactly. PTC in theory and practice does not independently register the presence of on-track equipment, but relies on the "legacy" train control system to register the presence or "occupancy" of the track. On-track (maintenance) equipment, unlike locomotives and railroad rolling stock, does not always trigger that legacy system to register occupancy. Hence,, all railroad operating rules prohibit train movement into a section of track used by on-track equipment. Similarly, on-track equipment is prohibited from occupying the track without the permission of the train dispatcher, who, when granting permission, will apply devices that prevent the display of signals that might authorize following or opposing movements.
Once the blocking devices are applied to signals that display "stop" PTC does its thing and sets a zero velocity target for trains approaching the signal.
So...either the on-track equipment occupied the track without permission; or gave the dispatcher the wrong information on what track they were to use; or the employee in charge of the equipment reported "clear" to the dispatcher before the equipment was fully in the clear; or the train dispatcher failed to apply or improperly removed the blocking devices and wrongly displayed a signal authorizing movement of the train (either through forgetting, or miscommunication in a transfer between dispatchers). In my experience, all these things happened at one time or the other. It's horrible when it happens and PTC is not configured to overcome this vulnerability.
@@sartesian , Thanks! I have zero experience with NTSB, railroads or PTC, and only minimal with automated systems from an operators view. Even as I made my initial statement about how I thought PTC worked, I was realizing there could be situations like you explain. As soon as I questioned if these trucks were actually “on track”? And if so would they trigger PTC? I also realized that the mere presence of equipment in the immediate vicinity of tracks could present virtually an identical hazard, that no sensor could detect. Then I started thinking that there must be a human factor still involved? I’ll do some reading on how the Legacy system is supposed to prevent things like this. Can you recommend a resource or public forum where thinking people are discussing this? I looked on railroad.net but couldn’t find anything. Watching news anchors & reporters bungle their way through 2 minutes is worthless.
The more I think about this, especially after reading your thoughts, it sounds much like the MCAS system failure that brought down 2 Boeing 737s. I’m not involved with aviation, but I went down that rabbit hole too!
I worked in lumber manufacturing. Our automated logic systems were often less than perfect, but the result of their failures was mostly some bad product, or a big mess to clean up. Trying to get sales, engineers, electricians, operators, managers, & accountants together on something was an art.
Glad no one was killed, but the rescuers are heroes for saving every soul on that train and or ones who were involved! But I know that it’s not just me that wants to see that onboard outward facing video!
Wow...you forgot to mention the REAL first responders...the brave citizens of San Bruno.
Paul pelosi got off dui napa???!!!
Typical government agency... leaving out critical facts in their media statement, Not one time did they mention that the train actually derailed from the impact.
Hi Eric, this is only an abstract of the statements that the NTSB has made - there was plenty of coverage before and after, of various quality and speculation by the media. NTSB is there not to make a "show' but to find out the cause of the mishap/accident, it is a very demanding investigative work without having all the speculators and lawyers around to disturb the investigation and get the viewers upset. I know, I have been there. Ciao, L