VOLKER LANDWEHRWhat PTC is required to do at "restricted speed" is found in 49 CFR §236.1005 linked above.
Then you are only discussing trying to prevent collisions between trains operating in signaled territory or on a joint authority mandatory directive.
This discussion then would not consider collisions in non-signalled territory, in tracks other than a main track or in yard limits, all of which would fall outside the scope of 49 CFR 236.1005.
That still presents the problem that you have to allow two pieces of equipment to (trains, engines or cars) to be able to come in contact with each other when operating in a signal system or in a joint manadatory directive. How do you tell the PTC system that you are adding an engine to the train intentionally, and that it is not a case of an engine running into a standing train? The difference between a collison and a coupling is intent.
Dave H. Painted side goes up. My website : wnbranch.com
dehusmanPeople first have to define what they mean by "enforce restricted speed". Restricted speed is designed to intentionally allow "collisions" between equipment.
We are not talking about intended collisions/couplings but "restricted speed", a speed that will permit stopping within one-half the range of vision.
What PTC is required to do at "restricted speed" is found in 49 CFR §236.1005 linked above.
Coupling cannot prevented by PTC as long as it doesn't know the location of every single car. That is unlikely to ever come.
At best it will perhaps sometime know the location of head end and rear end of a train to prevent "restricted speed" accidents like in Arizona.Regards, Volker
VOLKER LANDWEHR Euclid Euclid Are we talking about PTC as defined by the mandate or PTC as defined by its conceptual limits? You asked, I answered.Regards, Volker
Euclid Euclid Are we talking about PTC as defined by the mandate or PTC as defined by its conceptual limits?
You asked, I answered.Regards, Volker
Oh that's fine. I appreciate your ansnwer. I was just using it to frame the reason I asked the question.
EuclidEuclid Are we talking about PTC as defined by the mandate or PTC as defined by its conceptual limits?
VOLKER LANDWEHR Euclid Are we talking about PTC as defined by the mandate or PTC as defined by its conceptual limits? For the latter, PTC needs to be given eyes in the form of optical sensors. I think we are talking about the mandated PTC. Restricted speed was exempted from PTC except control of max. speed during the law making process for cost and time reasons.
Euclid Are we talking about PTC as defined by the mandate or PTC as defined by its conceptual limits? For the latter, PTC needs to be given eyes in the form of optical sensors.
I think we are talking about the mandated PTC. Restricted speed was exempted from PTC except control of max. speed during the law making process for cost and time reasons.
I think that is the correct interpretion of most references here to PTC. But I also think it is important to make the disctinction since there is a lot of oppostion to PTC because it has been mandated. And this opposition naturally results in trying to downplay the benefits of the PTC concept. So when people say "PTC can't do" this or that, it may be encouraged by active opposition to PTC because of resenting the mandate. So, in such a case, it serves the argument to leave out the qualification that the cited limitation only applies to the mandated PTC.
People first have to define what they mean by "enforce restricted speed".
Restricted speed is designed to intentionally allow "collisions" between equipment.
A train is made up of individual cars and engines. In order for them to operate as a train they have to intentionally "collide" to couple. If you prevent all "collisions", you will prevent equipment from coupling up.
The difference between a "coupling" and a "collision" is intent. PTC can't detect intent.
oltmannd tree68 oltmannd PTC can't enforce restricting because there's no way of knowing the end point of the authority. I would submit that PTC can't enforce restricted speed because it doesn't have eyes. The limits of restricted speed may be known. What is not always known is the conditions that require it. This would be why PTC would only enforce the maximum allowable speed under restricted speed. This could occur on main track. I wonder if PTC does enforce slow speed when restricting speed is indicated (such as being "talked by" a stop signal? Anybody know?
tree68 oltmannd PTC can't enforce restricting because there's no way of knowing the end point of the authority. I would submit that PTC can't enforce restricted speed because it doesn't have eyes. The limits of restricted speed may be known. What is not always known is the conditions that require it. This would be why PTC would only enforce the maximum allowable speed under restricted speed. This could occur on main track.
oltmannd PTC can't enforce restricting because there's no way of knowing the end point of the authority.
I would submit that PTC can't enforce restricted speed because it doesn't have eyes.
The limits of restricted speed may be known. What is not always known is the conditions that require it. This would be why PTC would only enforce the maximum allowable speed under restricted speed.
This could occur on main track.
I wonder if PTC does enforce slow speed when restricting speed is indicated (such as being "talked by" a stop signal? Anybody know?
Slow Speed and Restricted Speed are not the same. When operating at Slow Speed there is no requirement to be on the lookout for the things that are mentioned in the rule book definition of Restricted Speed.
Never too old to have a happy childhood!
EuclidAre we talking about PTC as defined by the mandate or PTC as defined by its conceptual limits? For the latter, PTC needs to be given eyes in the form of optical sensors.
PTC systems can be designed to know the rear end of a train. Look at stand-alone systems allowing moving block like the approved CBTC. https://en.wikipedia.org/wiki/Communications-based_train_control
I-EMTS is not able to this in its current design status.
There will still be reasons for restricted speed like broken rails that might not get detected precisely enough to use PTC.
A differently mandated PTC could have prevented the Arizona accident, I think.
The upper limit of restricted speed is controlled by PTC according to 49 CFR §136.1005 (f): https://www.law.cornell.edu/cfr/text/49/236.1005Quote: (f)Train-to-train collision. A PTC system shall be considered to be configured to prevent train-to-train collisions within the meaning of paragraph (a) of this section if trains are required to be operated at restricted speed and if the onboard PTC equipment enforces the upper limits of the railroad's restricted speed rule (15 or 20 miles per hour)............Regards, Volker
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
BaltACD oltmannd There is two way communication from the train to the back office. Trains have to tell the back office that the data has been received and is in good shape. Train also have to "release" the movement authorities they have used. Kind of like reporting clear in manual block. Trains don't do the reporting - track circuits in signalled territory do the reporting. Train crews do the reporting in TWC territory.
oltmannd There is two way communication from the train to the back office. Trains have to tell the back office that the data has been received and is in good shape. Train also have to "release" the movement authorities they have used. Kind of like reporting clear in manual block.
Trains don't do the reporting - track circuits in signalled territory do the reporting. Train crews do the reporting in TWC territory.
Correct, but PTC does it, too. It's not "vital", but PTC won't let out another movement authority for a following train until the leading train "clears up" behind it. It's "both/and" the way I understand it.
Are we talking about PTC as defined by the mandate or PTC as defined by its conceptual limits? For the latter, PTC needs to be given eyes in the form of optical sensors. As I mentioned in the other thread, there is no limit to amount of sensor coverage and sensor capabilities that could be applied to a railroad corridor. Sensors could be added to trains and also placed wayside to provide a fixed grid. They could sense anything that humans can see plus many things that humans could not sense.
Taken to its logical conclusion, it will be PTC that will ultimately decide what condtions require restricted speed; and it will be PTC that will then enforce restricted speed. So there will be no need for end points of authority because the application of restricted speed will be fully automated.
oltmanndPTC can't enforce restricting because there's no way of knowing the end point of the authority.
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...
oltmanndThere is two way communication from the train to the back office. Trains have to tell the back office that the data has been received and is in good shape. Train also have to "release" the movement authorities they have used. Kind of like reporting clear in manual block.
There is two way communication from the train to the back office. Trains have to tell the back office that the data has been received and is in good shape. Train also have to "release" the movement authorities they have used. Kind of like reporting clear in manual block.
That's kind of a funny question to ask. Operating under a resticting indication implies the condition of the track ahead is unknown. For a PTC movement authority to be given, you have to know the route is clear to the end point of the authority.
PTC can't enforce restricting because there's no way of knowing the end point of the authority.
A train running in PTC mode might have to make a move governed by a restricting indication, such as entering a yard, but at that point it is no longer on PTC covered track.
Increasing levels of complexity result in increased level of cost.
How much PTC safety can you afford to buy? How much would the additional complexity add to the time necessary to implement the finished product?
Remember, PTC as a product - DID NOT EXIST - when Congress mandated it without providing the railroads any funding mechanisms to get the job done. A number of disjointed technologies that can be brought together after much hard work did not make interoperable PTC a easy product to design, standardize and implement on the Class 1 railroads. Note - what Amtrak has implemented on the NEC as their version of PTC is not interoperatable with the form of PTC that the Class 1 railroads are implementing on their properties and the systems that the Amtrak Long Distance (non-NEC) trains must operate on.
PTC is a involved system at present. I suspect, over time, enhancements will be made as the carriers see opportunities to make PTC more effective and ALSO reduce the costs of operating trains and maintaining signal systems.
Several people have asked recently why PTC does not absolutely preclude collisions between trains at restricting speed.
I'm not a PTC expert so someone who knows more can correct me. But the simplest explanation is that the PTC data network is basically one way: data goes to the train from either the railroad's communication network or the signal infrastructure, but it does not go the other way. The infrastructure passes its information to the train, the train determines its own position using GPS, and from those two sources of info the on-board computer enforces the various signal indications, authorities, and restrictions.
I'm not saying there aren't radio communications going in both directions - presumably the train can acknowledge having received a message and things like that. But I'm fairly certain that the system does not require a train to send vital, real-time location information back over the PTC data network. So in fact PTC doesn't give Train A any information about Train B's location. Train B's location is known in the same manner as before PTC came along: track circuits in signaled territory, track warrant limits in dark territory. So the way you pull up close to another train is the same as it was before: go slow enough to stop before hitting whatever might be out there, wherever it might be within the block.
Yes, there probably are ways to enhance the current system to prevent some additional low-speed collisions. My bet is that you would have to more or less implement moving blocks, which is to say, it's a long way off.
And finally it's worth pointing out that Restricted Speed is required to prevent or mitigate many things besides train-to-train collisions: broken rail derailments, train vs runaway rail cars or cars improperly left on the track, trains vs MOW equipment, trains versus track or signal workers. Incorporating these into even a really fancy PTC system would be very tricky indeed.
Dan
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