Ten90 Solutions LLC

On October 9, the Railway Age website published an interesting article by Dr. Carl Nash entitled "PTC, a different approach."

Dr. Nash argues: 1) railroads are wasting money on duplicative PTC systems that require "very large numbers of expensive, high maintenance and probably unreliable trackside sensors to monitor train position and speed."

2) adapting the WAZE/Google auto/road navigation system for railroad use would be "relatively easy."  The relatively easy adaptation would include speed limits for all sections of track, positions of all switches, and warning and enforcement modules so that in the event the engineer ignores the warning, the system "will automatically apply the train brakes."

3) the position and speeds of all trains,  all switch positions, and all maintenance locations would be sent through satellite communication to central control, "where it would be monitored to determine a potential collision between trains."

4) All of this, including a "proximity warning system," currently used on automobiles could be done cheaply across the entire general railway system.  How cheaply?  Less than $1 billion dollars cheaply. 

Well said I, after recovering from the force of the blow of my own hand hitting my own forehead when I said, "why didn't I think of that," why didn't I think of that?  Because it's incorrect.  Because it is not an accurate representation of technology, equipment, or necessary functioning of the railroad PTC systems, particulary I-ETMS and ACSES.  Maybe because it never addresses the real problems involved in the development, validation, and deployment of the railroad PTC systems. 

I'll leave the issues of waste and duplication for others, but I do want to point out that unlike public streets and highways, railroads did not develop and do not exist as public property with universal access. Railroads developed as and continue to be private property with restricted access, and the different legacy systems of train control in use on the railroads developed from exactly that history.  PTC systems on the major railroads, including Amtrak's NEC, are not designed to supplant that legacy but in fact overlay that legacy, for better or for worse.  Interoperability is a problem to be solved, not the starting point as it is in a navigation of public access roads and highways. That's one.  That creates waste and duplication?  Maybe, but it's where we have to begin.   

Next, neither I-ETMS nor ACSES employs large numbers of "probably unreliable trackside sensors to monitor train position and speed."  Both systems are "locomotive centric" meaning position and speed are derived from signals transmitted, and processed, on-board the locomotives.  For I-ETMS, location is provided by GPS systems, which also provides a speed input.  Speed values are also checked against values derived from tachometers but there is no "monitoring"-- watching over-- the speed of the train by "trackside monitors."   

ACSES utilizes in-track, not trackside, sensors, called balises to transmit a message identifying the balise location to the train and the distance to the next message transmitter, including upcoming speed restrictions.  Monitoring the speed however is performed on-board the locomotive, not by the balise system. 

In both system continuous speed monitoring, including warning and enforcement is processed and initiated by the on-board equipment. Location is also calculated by the on-board equipment through reference to external and internal signal inputs. 

Just for information's sake, I'll point out that well before the PTC mandate, more than 50 percent of the general railway system's tracks have been equipped with an extremely reliable, not really that expensive, but demanding of maintenance, system of track sensors to monitor train location, called-----track circuits.  Track circuits are so reliable, dependable, accurate in determining train occupancy, that we literally stake our lives on them.   

As for easily adapting the WAZE/Google navigation systems... well it can be adapted, but so what?  That adaptation, the mapping of railroad track system, the conversion of the actual geography and topography through and upon which the railroad operates has been accomplished.  Was it accomplished at a greater cost than that of the WAZE system?  Probably, but the data obtained has to be so much more complete, dense, and detailed for railroad operations. Why?  Because that detailed, dense information is critical to developing the braking algorithms that ensure safe train separation.

I know very little about the WAZE system.  Never used it.  According to Dr. Nash, the system "provides not only information on where roads go...it also monitors traffic to show what the most rapid route is likely to be."  No offense to anyone, but railroads don't really require that last bit of information.  Railroad are fixed guideways and to mitigate congestion, we have to schedule train movement through time and space, utilizing as much time and space as we can for all movement while minimizing the time any single train spends in any single space between terminals.   

Now contrary to what Dr. Nash claims, switch positions on the railroad are not detected by GPS systems.  I think this is the source of Dr. Nash's confusion about the high number of "trackside sensors" deployed with I-ETMS system.  To my knowledge, no current GPS system is accurate enough to distinguish between the "open" and "closed" position of switch points, or the "normal" and "reverse" positions of a switch or crossover. 

Just for the historical record, long before the PTC mandate, railroad have had, again on over 50 percent of tracks a highly effective reliable switch position indicator at, and between interlockings, called "signals." 

Anyway, in "dark" non-signal territory, switch positions are monitored by wayside interface units (WIU),  connected directly to the switch and configured to detect and communicate switch position via wireless radio, not GPS. 

WIUs are also used to transmit signal indication and information directly to the locomotive (not to the control center), and that information is used by the warning and enforcement modules on-board the locomotives to establish mandatory speed and braking requirements. 

In all cases, GPS systems are not even capable of receiving such information from switches and signals and initiating an action based on the information. GPS satellites are "transmit only" and the earthbound receivers are "receive only."

And so we come to the "relative ease" and cheapness of including warning and enforcement and automatic brake initiation systems with WAZE.  Dr. Nash refers to the "$1000" expense to equip an automobile with a "proximity warning system," or automatic braking when an obstruction is detected. 

Again I confess, I don't know how the proximity warning systems on automobiles work, but I figure that, like trains, there must be a braking algorithm involved that requires inputs of speed, vehicle weight, rates of acceleration and deceleration, and distance (among other things) to determine whether or not to initiate a brake application.  The range of those variables such as weight and length and distance are, when compared to train, relatively simple.  Train weights are in the thousands of tons.  Train lengths are in thousands of feet and train length is a critical variable as the length of the train, as well as the presence or absence of distributed power, and/or an End Of Train (EOT) device capable of initiating a brake application from the rear of the train, will determine the required time from the moment a request is make for brakes to the moment the brakes have effectively applied on all cars of the train.   

I don't know what the value of a "proximity awareness system" is when it takes 6000-11000 feet to stop a freight train.  The trick is to continuously monitor and enforce the proper speed from any point to the targets-- the targets being the restrictions to the train's authority for movement, and the ultimate limit to that authority.   

The point is that developing the braking algorithms to ensure safe train separation, and safe train operation, on a railway is a much more complex challenge than developing a proximity awareness systems for an automobile.  The braking algorithm has to account for train variables, and topographical variables-- curvature, track gradient, etc. 

And again, for the record, I'll point out that long before the PTC mandate, more than 50 percent of the general railway system already had a highly reliable, effective, maintenance requiring proximity warning system, again based on track circuits.  We call it automatic block signaling.  So reliable a system is it in fact, that PTC systems will enforce those signal indications, not supplant them.   

I know PTC development and deployment is a time-consuming and expensive job, but I don't believe that time is being wasted, and I don't believe that expense is due to the railroads' reluctance to "let Google do it." 

David Schanoes

October 18, 2018