Mike, that's all very interesting......... if you are interested. My comments on this thread have been limited, by one simple fact, I don't have much interest in current or future rail technologies.
So, since I'm really not interested, I will choose to leave you to it, and not invest any more thought into that part of the subject.
My interests lie in those Western Maryland mixed helpers I described, or in the B&O using diesel pushers on steam powered trains on Cranberry grade, and other similar grades.
As for self driving Teslas, that is way outside my interests.......
I was once well rounded until I learned what I really like........
Sheldon
gregc seems that consists and distributed power have been around since 1913 (at least on RDG) do i see 3 consists in this picture
seems that consists and distributed power have been around since 1913 (at least on RDG)
do i see 3 consists in this picture
Some where packed away right now, and not available digitally, I have a series of pictures showing the Western Maryland moving about 75 hoppers out of one of their mine branches with two Consolidations on the head end, three Alco RS diesels in the middle, and two more Consolidations on the rear, about 1950.
Many of their mine branches had very sharp curves, steep grades, and lighter trackage that made larger power not suitable.
So seven locomotives, five crews, to move 75 hoppers about 70 miles - typically took all day. But two or three smaller trains would have actually required more than one day.
So all this talk about these fancy automatic controls these days is interesting, but not nearly as interesting as how those guys did this with a mix of steam and diesel all those years ago.
All thru the 40's and 50's steam and diesel was mixed for double heading, pushers and mid train helpers - and generally without radios either..........
greg - Philadelphia & Reading / Reading
LastspikemikeIs the dynamic behaviour of a MU hauled train mayerially different whether the locomotives are all at the head end or split mid train or even end train?
Yes. The purpose of distributing the power is to reduce drawbar forces. If you put all the power on the head end, all the tonnage is on the first drawbar. If you distribute the power, the total drawbar forces are lowered.
Second if you distribute the power you distribute the points from which a brake application are applied and released, that results in a quicker brake application, a shorter stopping distance and a quicker release means a quicker acceleration and both equate to improved fuel utilization.
Running multiple trains in close succession still is longer by teh disatnce between the trains. If you run a 15,000 ft DPU with 3 sets of power its 15,000 ft long. If you run 3 5,000 ft trains separated by 1000 ft, you now effectively have a train with a 17,000 ft footprint. Grade crossings are blocked longer, it takes longer to clear an opposing train, longer siding lengths are required, etc. Additional electronics are required to maintain the close separation.
And the benefits are......?
Dave H. Painted side goes up. My website : wnbranch.com
The other thing that has to be considered is where the additional power is placed in the train, how many tons ahead and how many tons behind.
Yes there is constant adjustment of the tonnage being pulled/pushed as the train goes around curves, and up and down grades. Other than a bulk train (coal, oil, grain, ans, etc) the tonnage varies across the train, different length cars are loaded to different tonnages so the effects of grades, up and down, varies across the train.
Lastspikemike gregc Lastspikemike Are there advantages to coupling the two trains together? besides, as the video said, there's fewer engineers, wouldn't separate trains be required to follow signals, need to be at least a block apart and not interfere with other trains. in other words, wouldn't seprate trains be extras? isn't a single long train more efficient? In times past sure. But nowadays it is childsplay to automate a locomotive and current MU setups must in fact do so. I raise the points for two reasons: does current MU technology actually make the engineer obsolete or could easily do so? Is the dynamic behaviour of a MU hauled train mayerially different whether the locomotives are all at the head end or split mid train or even end train? If the two sets of locomotives could each haul half the train as a separate train and automation can allow the trailing train to run the same track section and signalling area consecutively, very close behind the lead train, then why bother coupling the two trains? Indeed, what's to stop the railroads from essentially running nose to tail with many trains in succession all protected by smart cruise control already available for individual passenger automobiles and tested for transport truck convoy setups? Docklands Light Railway (DLR) part of London's underground system, although in reality, an elevated system has run fully automated now for a very long time, just firvexsmple of what was already feasible years ago. Real underground trains run very close together under some sort of computerized safety system, although each train has a driver at least nominally in control. It seems to me that the discussion about whether and where in the train the loads are taken up begs the question of whether MU is really two trains coupled because railroads are required to have at least "one engineer" nominally in control of the entire train or for some other reason. It is correct that the current state of technology would easily facilitate one engineer controlling multiple separate trains from one locomotive. Coupling is not necessary for control any longer.
gregc Lastspikemike Are there advantages to coupling the two trains together? besides, as the video said, there's fewer engineers, wouldn't separate trains be required to follow signals, need to be at least a block apart and not interfere with other trains. in other words, wouldn't seprate trains be extras? isn't a single long train more efficient?
Lastspikemike Are there advantages to coupling the two trains together?
besides, as the video said, there's fewer engineers, wouldn't separate trains be required to follow signals, need to be at least a block apart and not interfere with other trains. in other words, wouldn't seprate trains be extras? isn't a single long train more efficient?
In times past sure. But nowadays it is childsplay to automate a locomotive and current MU setups must in fact do so.
I raise the points for two reasons: does current MU technology actually make the engineer obsolete or could easily do so?
Is the dynamic behaviour of a MU hauled train mayerially different whether the locomotives are all at the head end or split mid train or even end train?
If the two sets of locomotives could each haul half the train as a separate train and automation can allow the trailing train to run the same track section and signalling area consecutively, very close behind the lead train, then why bother coupling the two trains? Indeed, what's to stop the railroads from essentially running nose to tail with many trains in succession all protected by smart cruise control already available for individual passenger automobiles and tested for transport truck convoy setups?
Docklands Light Railway (DLR) part of London's underground system, although in reality, an elevated system has run fully automated now for a very long time, just firvexsmple of what was already feasible years ago. Real underground trains run very close together under some sort of computerized safety system, although each train has a driver at least nominally in control.
It seems to me that the discussion about whether and where in the train the loads are taken up begs the question of whether MU is really two trains coupled because railroads are required to have at least "one engineer" nominally in control of the entire train or for some other reason. It is correct that the current state of technology would easily facilitate one engineer controlling multiple separate trains from one locomotive. Coupling is not necessary for control any longer.
In the event of a required emergency stop, those "two trains" are going to be safer coupled together if they are as close together as you suggest.
There have been many discussions on the 1:1 forums and blogs about automated train operation, and systems like Trip Optimizer and Leader that attempt to do so. Suffice it to say that long North American freight trains are proving difficult to automate, in large part because the computers do not yet understand slack as well as a good engineer. I've also yet to see Trip Op get out and manually line frozen switches, or change the knuckle it just broke.
It does matter where you put the remote, and how many remotes you have, this will vary from train to train. As an example, a 200 car 30,000 ton loaded unit train requires 3 AC locomotives on our mainline. They are far easier to run when built 1x1x1 compared to 2x1x0.
They had also tried running such trains 2x0x1, but this led to some broken knuckles when cresting hills if you didn't put the fence up and throttle down the lead consist, as the front of the train would be accelerating downhill while the rear was still coming up.
Greetings from Alberta
-an Articulate Malcontent
LastspikemikeAre there advantages to coupling the two trains together?
dehusman gregc doesn't this mean you either want the head end consist pulling the entire train or the trail end consist pushing the entire train? Not if you have multiple powered consists. The whole idea of helpers or DP is to not have the head end consist doing all the work.
gregc doesn't this mean you either want the head end consist pulling the entire train or the trail end consist pushing the entire train?
Not if you have multiple powered consists. The whole idea of helpers or DP is to not have the head end consist doing all the work.
maybe there's a simple explanation of how this happens that doesn't require a computer either. (it would be nice to hear this explained by someone experienced).
presumably if both lead and trailing consist have the same # of engines and are at ~equal power (i.e. same notch) they provide the ~same tractive effort. but the acceleration each provides will depend on load (# cars).
presumably if "~all" the couplers are slack, the lead consist is pulling "~all" the train. the trailing consist is generating that same force but with little load, so it accelerates faster, bunching up couplers near the tail end of the train, increasing its load.
as more of the load is taken up by the trailing consist, it accelerates less and conversely, as fewer car are pulled by the lead consist, it accelerates more, changing the # of cars pull/pushed.
at some point, an apprpriate # of cars are pulled by the lead consist and pushed by the trailing consist such that their accelerations are ~equal and they both maintain the same speed or increase/decrease speed at the same ~rate.
the # of cars pulled/push changes as the situation changes whenever the load on one engine shifts.
the lead consist of a train cresting a grade will start to accelerate and pick up more of the load as more cars crest the grade. the trailing consist will accelerate as its load is reduced. the "balance" changes constantly as the train crests the grade and will reestablish itself once the train is on level grade. a similar rebalancing occured when the grade changed
this balance, # of cars pull/pushed is maintained by physics. no computers required
gregc...what do "dynamics" and "power" mean in this context?
And yes, you could keep the head end in dynamic and the rear in some power notch even after the slack had run in. This would be like having the rear pushing on the whole of the train resistance plus the braking resistance of the lead locomotives -- wasteful in a sense, but safe within limits (which Jeff can describe far better than I could try to do).
doesn't this mean you either want the head end consist pulling the entire train or the trail end consist pushing the entire train?
In particular this gets around the issue in long trains where you have a mix of grades and resistance that has parts of the train in 'tension' and other parts in 'compression'. I remember an engineer on either CNJ or LV explaining that there might be four or more such variations in a particular train... and part of professional train handling involved both recognizing and knowing how to manage the consequences.
[/quote]...or is the ideal case where half the cars between two consists are pulled and half pushed, where all the couplers are stretched in the half cars behind the lead consist and the couplers are bunched in half the cars front of a trailing consist?[/quote]For best theoretical economy you might run that way, and I often see (and hear) things like unit coal trains with reasonably consistent drawbar characteristics and no irregular patches of long-travel cushioned draft gear that are running with the node 'balanced' at the point corresponding to the power distribution. (For example we had loaded trains westbound on the ex-Southern from just east of the University of Memphis campus to Collierville that ran with 2 units on the point and one DP rear, and the node could be observed to be about â…” back in the train as it ran over the somewhat irregular track profile.
However even slight power or speed changes could and did result in noticeable banging as the node moved, sometimes at surprisingly high speed, forward or back in the train.
do locomotive couplers have strain gauges that report the drawbar force in the cab?
one of the videos said a benefit of distributed power is to reduce the force on the first coupler between the lead consist and car, allowing much longer trains. with ~equal power in a trailing consist, this force could be cut in ~half. does this suggest that if a train were stopped on a slight grade (e.g. 0.1%) where presumbly all the coupler slack was stretched, the trailing consist should run (?) first to remove coupler slack in most of the train before the lead consist begins applying power?
does this suggest that if a train were stopped on a slight grade (e.g. 0.1%) where presumbly all the coupler slack was stretched, the trailing consist should run (?) first to remove coupler slack in most of the train before the lead consist begins applying power?
gregcwhat do "dynamics" and "power" mean in this context?
Dynamic brakes and power is, well power, the throttle is above idle and pulling.
gregcdoesn't this mean you either want the head end consist pulling the entire train or the trail end consist pushing the entire train?
gregcdo locomotive couplers have strain gauges that report the drawbar force in the cab?
No.
jeffhergertIt's possible to place the head end into dynamics while having the DP consist(s) in power.
what do "dynamics" and "power" mean in this context?
jeffhergertIdeally, you want the slack either bunched or stretched.
or is the ideal case where half the cars between two consists are pulled and half pushed, where all the couplers are stretched in the half cars behind the lead consist and the couplers are bunched in half the cars front of a trailing consist?
one of the videos said a benefit of distributed power is to reduce the force on the first coupler between the lead consist and car, allowing much longer trains. with ~equal power in a trailing consist, this force could be cut in ~half.
obviously i have no understanding of this except for the physics. would this never happen, happen often or easily handled by an experenced engineer?
gregc dehusman The brakes need to be applied to the whole train ASAP to maximize the braking effort and reduce train line forces. If you apply brakes on the rear end first, then the chances of breaking the train in two is increased. this is interesting. i can understand that it may be ideal that brakes be applied to all cars simultaneously, but my understanding is this is impossile with current air brakes. that brakes are applied to cars starting with the cars closest to the source that the brakes are released from. if there is a single consist at the front of the train, brakes get applied to the front of the train first resulting in "coupler slack (?)" being lost toward the rear of the train and the train "bunching up (?)" (i don't know wat the proper terms are for these behaviors). if there are engines at each end of the train, this means from each end and that braking occurs last to cars in the middle of the train. if there are engines in the middle of the train, it further "equalizes" the application of the brakes resulting in brakes being more evenly "applied to the whole train ASAP". as an (electrical) engineer i assume that being able to independently control power and braking at different parts of the train would improve control. i don't assume a (locomotive) engineer would know what to do with this control, but assume a computer could. an engineer would tell the computer what he wanted to do and the computer would figure out how i assume there are certain situtations where this would be most useful possibly going up/down a grade on a curve, cresting a hill or (??)
dehusman The brakes need to be applied to the whole train ASAP to maximize the braking effort and reduce train line forces. If you apply brakes on the rear end first, then the chances of breaking the train in two is increased.
this is interesting.
i can understand that it may be ideal that brakes be applied to all cars simultaneously, but my understanding is this is impossile with current air brakes.
that brakes are applied to cars starting with the cars closest to the source that the brakes are released from. if there is a single consist at the front of the train, brakes get applied to the front of the train first resulting in "coupler slack (?)" being lost toward the rear of the train and the train "bunching up (?)" (i don't know wat the proper terms are for these behaviors).
if there are engines at each end of the train, this means from each end and that braking occurs last to cars in the middle of the train. if there are engines in the middle of the train, it further "equalizes" the application of the brakes resulting in brakes being more evenly "applied to the whole train ASAP".
as an (electrical) engineer i assume that being able to independently control power and braking at different parts of the train would improve control. i don't assume a (locomotive) engineer would know what to do with this control, but assume a computer could. an engineer would tell the computer what he wanted to do and the computer would figure out how
i assume there are certain situtations where this would be most useful possibly going up/down a grade on a curve, cresting a hill or (??)
The DP consist(s) can't have their air brakes applied/released independently, but the DP consist(s) can be controlled independently when it comes to power or dynamic braking. It's possible to place the head end into dynamics while having the DP consist(s) in power.
The throttle/dynamic brake use and proper use of the air brake can control slack movement in the train. (At least to a point. On some of the land barges they like to run now there are places you can do everything right and still break apart.) Ideally, you want the slack either bunched or stretched. It's how fast or harsh the changeis made from one condition to the other that can lead to problems like a broken knuckle or pulled out drawbar.
Jeff
In principle it's really simple, although people seem to love overthinking it philosophically
Each locomotive contributes its tractive effort to the load, through whatever behind it is also pulling on the load. That's how steam locomotives 'divide the effort' when double- or multiple-heading. When helpers push on the rear it can be just as with DPU; the helpers can 'push' a certain number of cars, the lead consist pulls a certain number of cars, and the point of 'zero slack' between them (where the effective 'tractive' effort goes to zero; we call it the 'node') can move backward and forward, sometimes at high speed, just as most of us have experienced with DP trains.
Conventional diesel-electrics take this a little further: each independent traction motor is geared to a particular axle, and takes up its share of the load automatically. A relatively modern AC locomotive controls the motors either in groups of 3 (using two inverters) or individually (using six inverters) carefully adjusting the power if urn wheelslip is detected, but otherwise adjusting the traction-alternator field to suit the commanded engine rpm.
Diesels are funny; they use a comparatively high percentage of their developed combustion horsepower for compression, so the faster they turn the more fuel they consume -- loaded or unloaded. And the eight-notch (actually binary relay logic-determined!) models the action of a solenoid-controlled governor in adjusting engine speed -- via fuel admitted. (The notch commands a 'governed speed', really a range of speed, and the mechanism of the governor then provides more or less fuel at the injectors to produce that ... but this is engine speed, not wheel rpm or train speed, just available power at a given generator rpm. (FADEC/EFI does this more intricately, but with an eye toward electrical compatibility with locomotives with mechanical Woodward governors, so the effect is the same.)
Now, there are other considerations about when a consist starts to become a lashup. One is different effective gear ratio (pinion and bull gear varies just as car differential "rear end ratios" can, and with the same quantization by integral numbers of teeth, with wherl diameter and state of tread wear complicating things) with freight units having higher mechanical advantage. This mattered more with DC motors, where temperature rise governs minimum rpm and 'centrifugal force' governs maximum rpm ... but remember I said that every axle contributes its own pull? What the limits mean is that a given consist is load-limited at low speed by the limitations of the least capable axle, and speed-limited by what may be a different least capable axle ... and of course, overall, by the traction the axles can achieve (or fail to achieve for the variety of reasons we've discussed over the years).
What is NOT automatic is the rate at which units in a consist load. GEs in particular are notorious for avoiding pollution and visible smoke by taking their sweet time to accelerate to speed and then load the engine to needed fuel consumption at that rpm -- in the bad old days this could take 30 seconds or more. Meanwhile other locomotives can load more quickly -- meaning they take more than their share and nuzzle against or try to run away from slower-loading units. Theoretically you can engineer most of that behavior out -- but locomotive manufacturers have not made that a control priority...
SD70DudeOn CN that feature was tried and found to be problematic, as the EOT's valve would tend to stick open.
you would think such a thing should be thoroughly tested and possibly have redundant values so that even if one stuck open the other wouldn't.
on the other hand, if it's designed to be used in case of emergencies, wouldn't it be more important that it is guaranteed to open than closes afterwards?
gregc gmpullman A modern EOT or end of train device will allow controlled or simultaneous brake pipe reductions from the rear, too. This type is in development but the current EOTs will allow an emergency application from the rear. No need for a locomotive to apply brakes from the rear thanks, i wondering about that too
gmpullman A modern EOT or end of train device will allow controlled or simultaneous brake pipe reductions from the rear, too. This type is in development but the current EOTs will allow an emergency application from the rear. No need for a locomotive to apply brakes from the rear
thanks, i wondering about that too
On CN that feature was tried and found to be problematic, as the EOT's valve would tend to stick open. This caused a few train separations as the tail end of the train would brake harder as the brake pipe pressure dropped.
I can also see it causing an unintentional release if the valve stuck open for a bit too long and then shut itself, causing the rear brake pipe pressure to drop lower than intended and then rise again as the pressure-maintaining feature of the locomotive brake valve tried to compensate for it.
We haven't used it for some years now, and there are standing instructions to disable it if we find a locomotive or EOT that has it enabled.
It was called "Brake Assist".
gmpullmanA modern EOT or end of train device will allow controlled or simultaneous brake pipe reductions from the rear, too. This type is in development but the current EOTs will allow an emergency application from the rear. No need for a locomotive to apply brakes from the rear.
An EOT would be able APPLY the brakes, but it won't be able to RELEASE the brakes. To do that you need an air compressor and there is no way an EOT could have that big of an air compressor and hang on a coupler.
gmpullmanA modern EOT or end of train device will allow controlled or simultaneous brake pipe reductions from the rear, too. This type is in development but the current EOTs will allow an emergency application from the rear. No need for a locomotive to apply brakes from the rear
mobilman44 Geez Sheldon, I do understand how a diesel loco works. I feel bad that my question exposed all that guessed at ignorance you dug up. Others before you answered my question, and I guess I just marvel at how a consist of various different locos could pull/push together without fighting each other. In the future, I'll be a lot more selective of what questions I ask here. Ha, whoever said there was no such thing as a stupid question was obviously wrong. Shame on me........
Geez Sheldon,
I do understand how a diesel loco works. I feel bad that my question exposed all that guessed at ignorance you dug up.
Others before you answered my question, and I guess I just marvel at how a consist of various different locos could pull/push together without fighting each other.
In the future, I'll be a lot more selective of what questions I ask here. Ha, whoever said there was no such thing as a stupid question was obviously wrong.
Shame on me........
No worries, my apologies, your question seemed so basic and the answers quickly went into a lot of detail down a lot of paths.
Simple answer is because all these powered axles are not linked mechanically, the application of power balances out, mostly......
It is one of the virtues of electric traction.
gregcif there are engines at each end of the train, this means from each end and that braking occurs last to cars in the middle of the train.
A modern EOT or end of train device will allow controlled or simultaneous brake pipe reductions from the rear, too. This type is in development but the current EOTs will allow an emergency application from the rear. No need for a locomotive to apply brakes from the rear.
Regards, Ed
ENJOY !
Mobilman44
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
dehusmanThe brakes need to be applied to the whole train ASAP to maximize the braking effort and reduce train line forces. If you apply brakes on the rear end first, then the chances of breaking the train in two is increased.
Railroaders who operate 1:1 equipment but do not model would probably not understand his joke about matching locomotive speeds. Granted, you'd be unlikely to run into such a person on a forum like this.
I've seen that line a few times over the years in various places online, and I've even heard it in person out at the museum (along with "what kinda transmission's in that thing").
gmpullmanThe Bessemer & Lake Erie ran them like that for a while, too. Albion, Pa. to Conneaut, Ohio ore docks.
Cool. The CN uses 2 B&LE tunnel motors as helpers on Byron Hill, which is just south of Fond du lac, WI.
Mike.
My You Tube
I could be wrong here, and Mobilman44 should speak up and say so if I am.
But I took his question to simply mean MU'd diesels, not modern DP, and him wanting to understand how one engineer controls 2 or more locomotives without them fighting each other like our models sometimes do.
This question, if I am right, suggests that the OP does not fully understand how a diesel electric locomotive works, let alone how how three or four of them respond to one set of commands.
Maybe he needs to understand how the traction motors are connected to the wheels and the fact that a real locomotive will roll when pushed, while our models will not.
And how the traction motors are controlled electrically and how the diesel engine and the traction motors respond to the commands from the engineer.
Maybe he needs to first understand how the four or six traction motors are separately geared to their individual axles and how they work together to move the locomotive.
Then it will make more sense to him how one set of commands can control multiple locomotives with minimal "conflict" as all these separately powered axles apply power to move the train, differently from our models with one motor applying power thru worm gears that will not free wheel.
Again, I could be wrong, but I think the OP is asking a more simple question than most of you have been trying to answer.
And now the irony in this, I am DC modeler, and nearly every train on my layout is powered by more than one powered locomotive. And while many are relatively "matched sets", I also run double or trippled headed steam of mixed brands and wheel arrangements.
Example, a Spectrum 2-6-6-2 and a Proto 2-8-8-2 on the head end of a coal drag of 40-45 hoppers. They run fine together, no modifications, nothing done to "speed match" them.
Generally, if you really need two or more locos, and the starting voltage and gearing is close, they will run fine together.
So, maybe, the OP just needs to understand how the real diesel electric locomotive works in the first place?
Maybe his question was confusing because he was not sure what terms to use?
Or maybe I'm all wet?
RE: the sparky video of excessive wheelslip, that was probably caused by a defective wheelslip sensor or control module on that particular unit.
Here's a TSB report on a runaway that happened as a result of poor train handling, but a key link in the chain was an emergency brake application that happened as a result of the safety features built into the Locotrol II system:
https://www.bst-tsb.gc.ca/eng/rapports-reports/rail/1996/r96c0086/r96c0086.html
gregcwhile watching the videos i wondered how brakes were controlled and if brakes could be applied from the trailing unit, at least at first, presumably from obvious reasons?
Generally the brake application is applied from each of the remotely controlled engines at the same time in order to minimize the transmission time through the train line. The brakes need to be applied to the whole train ASAP to maximize the braking effort and reduce train line forces. If you apply brakes on the rear end first, then the chances of breaking the train in two is increased.
and similarly if brakes could be released from the head unit?
Why? That'ts what regular brakes do. The goal, once again is to release the brakes ASAP across the whole train.
can brakes for any consist be independenly controlled, and for units in the middle of the train, can front and rear brake connections be independently controlled?
The train line runs the length of the train. Any changes in pressure will be propogated throughout the the whole train line eventually. If you set or release the brakes on just part of the train you will end up with brake in twos or runaways.
thanks
fly-by-wire was developed during the space shuttle era as a means to control an aircraft electrically via computer or even remotely (!!). initial systems only gave the computer 20% control which was presumably enough to relieve the pilots of the need to make frequent adjustments reducing fatique.
another feature prevented pilots from exceeding limits. this was modified since the pilot is the best person to make that decision when his life is on the line. such intelligence often takes time to sort out.
while watching the videos i wondered how brakes were controlled and if brakes could be applied from the trailing unit, at least at first, presumably from obvious reasons?
and similarly if brakes could be released from the head unit? can brakes for any consist be independenly controlled, and for units in the middle of the train, can front and rear brake connections be independently controlled?
and with regard to power, why can't the computer independently control power on various units to at least maintain a desired speed, if not acc/deceleration, or even coupler force?
Mark Cole, who helped write the ATSF manual for Locotrol II in the mid-'80s just before the aborted SLSF merger, noted that in the revision from the original to II, the Harris engineers incorporated "too many safety items which caused the trains to go into emergency whenever something wasn't exactly what the equipment required". I suspect much of the way later versions handle 'indefinite LoS' was "informed" by such experience.
There can be issues with the loss of signal. I still remember the original uncensored video of the Panhandle wreck, where the head-end radio was destroyed on impact and the DP kept pushing the train into the developing dust cloud...