Heard the News?

Big news from last week, and believe it or not, it had nothing to with Precision Scheduled Railroading, or the constitutionality of an impeachment trial when the impeached has retreated to the east coast of Florida.

Is such a thing even possible? Apparently so, because it was announced last week that several employees of BNSF received a patent in January 2021 for a “moving block system.” Turns out upon closer examination, the patented invention is not for a moving block system, but a fixed block system that is partitioned into a number of virtual track blocks within each fixed block. By detecting the presence or absence of “electrical circuit discontinuity” a virtual track occupancy or non-occupancy by a train can be derived for each of the virtual track blocks.

Full disclosure: I am not a signal engineer, an electrical engineer, a IT engineer, any sort of engineer, including locomotive engineer. My “expertise,” such that it is in the area of signaled train control, is derived from the patient explanations of principles and practices of safe train separation provided to me over many years by the extremely talented and dedicated designers, managers, and practitioners of signal based train control at Metro-North Railroad. I never miss an opportunity to express my gratitude to them all, from track level maintainers to department chiefs. I don’t have to mention names. They know who they are. However, I will mention one, Walter “Bud” Jackson, who passed away in 2017. He embodied the very best of the best practices in executing the installation of train control systems, and he never tired of trying to remedy my inexhaustible ignorance.

My ignorance remains inexhaustible, so any mistakes, errors of comprehension should not reflect on the efforts of those who tried to cure me.

What I do understand about train control systems, from the very beginning of such systems in the operating rules and timetables, through telegraphic delivery of train orders, through block signal systems manual and automatic, to microprocessor based systems, is that everything is based on a simple logic: everything is “if, then;” “yes” or “not-yes;” “no” or “not-no;” “on” or “not-on;” “off or “not off;” “1” or “0.” It’s a binary world, or world, at least at this non-molecular level, and you either are or are-not, and no fuzzy logic is allowed, much less necessary.

I’m not trying to offend anyone who bridles at the constraints of the binary world, but then, I usually don’t have to try. Just comes naturally to me.

Anyway, that logic is the way we have to do things to control the movement of trains; to prevent aberration from becoming chaos; to manage risk. The fact that I’m personally a confirmed binary might have something to do with my gravitation to, my affection for, my advocacy of the simple logic behind vital train operations but it does not diminish the validity of that logic.

The information pertaining to the patent grant can be found here.

I think I understand it. I’m not sure I understand how it works, but I believe I understand the claim for the way it is intended to work. Unfortunately, I just can’t call up my “mentors” from the C&S department and go over the document line-by-line, although if anyone, less ignorant than me, would like to do that, please email me at dmschanoes@ten90solutions.com and we’ll arrange a call.

Basic features of the proposed system as I understand, or fail to understand, them:

a) the physical block, defined by insulated joints at the outer opposing ends, is partitioned into virtual track blocks

b) an electrical circuit discontinuity is made detectable in one of the virtual track blocks created within the limits of the physical track block and

c) the discontinuity is used to generate a code indicating “virtual block occupied”

d) the code, indicating virtual block occupied or not occupied is transmitted to a train following within the limits of the physical block

The patent applicants detail description of their invention stating: [Note– to understand the description it is important to review them with the drawings accompanying the application]

a)Two methods of train detection are employed. One method determines rail integrity [broken-rail protection] in an unoccupied block. The other determines the train’s position in the occupied block along with broken-rail protection.

b) The description identifies as Track Code A (TC-A) the “available open source electrocode commonly used by railroads and is carried by signals transmitted via at least one of the rails of the corresponding physical block. ”

c) Track Code B (TC-B) is particular to this invention and “provides for the detection of train position within one or more virtual track blocks within an occupied physical track block and is preferably carried by signals transmitted by at least one of the rails of corresponding physical track block.”

d)”TC-A and TC-B may be carried by the same or different electrical signals….Generally, TC-A is dependent on a first location sending a coded message to a second location and vice-versa… On the other hand TC-B is implemented as a reflection of the transmitted energy using a transceiver pair with separate and discrete components. With TC-B, the system monitors for reflections of the energy through the axle of the train.”

e) A Virtual track block position message that represents occupancy data is determined by analysis of TC-A and TC-B signals and transmitted to computers onboard “locomotives in the vicinity.”

f) “TC-A is preferably implemented by transmitter-receiver pairs with the transmitter and receiver of each pair located at different locations. TC-B is preferably implemented with transmitter-receiver pairs, with the transmitter and receiver of each pair located at the same location. The signature of the energy from the transmitter is proportional to the distance from the insulated joint to the nearest axle of the train.”

So this is what I get from the patent material: within each physical block various “signal houses” or CILs are established. Each CIL generates and transmits electrical energy to discrete “packets” of track, with the packets corresponding to “virtual” mini-blocks. Apparently, even with a physical block occupied, the energy transmitted from the intermediate CILS to the rails degrades (or upgrades) with not only detectable differentiation, but also with some sort of uniform, repeatable differentiation dependent on the distance from the insulated joint to the nearest axle of the train. This principle of a “regular,” repeatable, decline or increase in the reflection of the energy dependent upon distance has to apply to both the “occupying” or entry-point insulating joint and “clearing” or departing insulating joint. If this is so, then indeed within the physical block, virtual blocks can be established at a distance equivalent to the signal design distance to zero mph from the end of a leading train.

So my questions are

a)Does that principle apply under all conditions? Do soil conditions, weather conditions, ballast conditions affect the reflection of the energy or the measure thereof?

b)Are deviations from that principle calculable, explainable by the mechanisms associated with the principle itself?

c)Does the principle apply to trains of any length, of any weight, operating at any speed?

d)What is the level of precision, and the rate of error associated with measuring this reflection of energy from the insulating joint nearest the lead or trailing axle of train?

The patent document states: “One technique for measuring track position and generating TC-B is based on currents transmitted from one end of a physical track black towards the other end of the physical track block and shunted by the wheel of the train. Generally (emphasis added), since the impedance of the track is known, the current transmitted from an insulated joint will be proportional to the position of the shunt along the block. Once the train position is known the occupancy of the individual track blocks is also known.”

Generally, “generally” is not adequate, nor sufficient for determining track occupancy, and let’s be clear, we’re not determining location for a performance measurement, we’re determining OCCUPANCY for an authority for movement. There is a big difference, with the latter being a vital determination requiring a vital process that complies with the “either, or” “yes, no” “on, off,” “go, no-go” logic of vital train operations.

If the vital requirement cannot be satisfied in either reliability, or accuracy, and by failure into the safe, no-go mode then the system cannot be used for train control.

Moreover, even if the detection system satisfies those requirements, there is another variable that compels investigation, and that variable is true braking rates. We have long been concerned when analyzing the safety of train control systems with “true ground speeds”– how the locomotive generates, and recognizes, its true ground speed. Since this is a locomotive-centric system for determining, and enforcing, allowable speed, a true braking rate must be known.

We do this by algorithm, but I’m not sure we have sampled enough real circumstances with real limitations on braking forces to radically reduce train separations.

We are always involved in turning a a variable quantity, required braking distance, into a vital quality, i.e sufficient braking is always available regardless of train make-up to prevent overruns of authorities. But we always have required, and executed, safe braking tests to validate the safe braking analysis that keeps our nightmares bad dreams and not our awake life. As we reduce train separations, reduce our “buffers,” the reality of different train braking rates becomes ever more vital.

Patent or no patent, please prove the invention satisfies the requirements of vitality, and prove it to someone like me, in my inexhaustible ignorance.

David Schanoes

February 15, 2021

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  1. It appears to me that the principal purpose of this system is not for typical ‘block signal’ brake purposes, but to facilitate differential acceleration: if you have a train stopped in a siding, and a train in the same direction passes at a particular speed, the train in the siding can immediately follow and start accelerating in the same ‘block’. There is no immediate chance of collision, but the alternative is to wait until the relatively enormous distance of the fixed block is opened before the second train can even start to move. PROVIDED the micro block system can detect even catastrophic deceleration (as with derailment) of the first train and holds the speed of the accelerating train to something below what a full-service application would stop it from in the distance opening up between the two, you preserve safety.

    Not as good as good CBTC, of course, but as a deterministic overlay on ABS it is certainly better than nothing.

    1. The “principal purpose” for this system has to be the same as the principle purpose of block signal systems– safe train separation. That being said, a train can follow another train out of the siding once the leading train clear, not the complete block, but the signal (and overlap) at the controlled point of the interlocking. Even without CTC based systems, exit from the siding is possible, as hand throws, and even electrically locked switches can release behind the main track train. Acceleration isn’t the real issue here, given the time it takes trains to reach MAS from zero velocity.

      I think the gain in efficiency of the BNSF system shows up and is driven by reducing headways for trains operating at similar speeds for similar distances– increasing the number of “track slots” available, say, on BNSF’s Southern Transcon.

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