What PTC Is—and Isn’t

Written by Ron Lindsey, Contributing Editor

RAILWAY AGE, FEBRUARY 2021 ISSUE: It comes down to understanding the difference between technicians and technologists.

The article “PTC 2.0: Now is the Time” (RA, December 2020, p. 30) does not, in my mind, clearly define what PTC really is. The argument presented underscores my long-held contentions that technicians step in too quickly when what is needed first are technologists, and that some of the investment in meeting the largely unfunded federal PTC mandate has been misdirected. In this article, I offer several alternatives for the railroads, both individually and collectively, toward improving operations.

To start with, there currently is no “PTC 2.0.” Industry-wide, there is only one version of PTC, with some slight variations. PTC is and always will be a safety enhancement system. In that same vein, PTC is not even functionally vital, in that it does not generate movement authorities. That point alone prevents PTC from being directly involved in advanced management systems, as suggested by this excerpt from the article: “PTC systems also enable a railroad to run scheduled operations and provide improved running time, greater running time reliability, higher asset utilization and greater track capacity.”

— PTC prevents human-factor-caused train accidents. It does not improve velocity. —

PTC prevents human-factor-caused train accidents. It does not improve velocity. At best, it assures that velocity be maintained, based upon existing management systems and processes. In fact, if not properly implemented, for example, by using overly conservative braking algorithms, PTC can result in velocity reduction due to inappropriate enforcements. It is not uncommon to hear the term “Vital PTC,” but understand that it refers to equipment’s hardware vitality, not its functional vitality. As such, it provides only for some level of reliability.

PTC implementation provides an onboard intelligence platform and a wireless data network for back-office system handling and transmission of train speed and position. PTC by itself does not require this. To be blunt, all that is needed for advanced systems is an onboard GPS and a wireless data network to deliver train speed and location data with some level of frequency determined by the management systems being used. I refer to this as “In-Time,” rather than “Real-Time,” with the latter being a technician’s common design error.

Prior to the 2008 mandate, the Federal Railroad Administration’s (FRA) concerted efforts at getting the railroads to implement PTC was limited to demonstrating that PTC would have sufficient safety benefits to justify an investment. A Railroad Safety Advisory Committee (RSAC) study facilitated by the FRA was unable to identify sufficient safety benefits. So, FRA turned to business benefits.

But there are only two such possible business benefits that can be attributed directly to PTC. First is train accident prevention. Second, PTC’s safety gain could enable cost reductions, such as transitioning to dark territory from signaled territory, providing a net safety gain. But the mandate forcing PTC implementation, with railroads carrying the financial burden, changed analysis to determining how best to “profit” from the sunken cost. But who is available to make such analyses?

Technicians are the source of safety and maintenance integrity. As such, their natural mindset is to design, test and install to the upmost. Cost effectiveness is second to safety, and everything is vital as to hardware and functionally, even when it isn’t, e.g., signal aspects and PTC. Management will accept designs without regard to costs because they have no one else to challenge the cost-effectiveness of other solutions using different technologies. In the case of PTC, no one challenged the integration of Intermittent Signals in its enforcement functionality. The money required to include Intermittent Signals was unnecessary, since PTC looks at distant control points. I have yet to be challenged on this point by anyone over the past 12 years. 

— A technologist would first determine what is required for positioning accuracy instead of shooting for an unnecessarily high level by addressing non-vital PTC’s weakest component, the braking algorithm. That algorithm is subject to variables that often are not even known as to value, yet alone their coefficients. —

Another example is even more troublesome. The technicians on the Interoperable Train Control (ITC) committee set up by the industry to make PTC implementable solicited a contract to develop an on-board positioning module with an 18-cm accuracy and 10-9 confidence level. That is inconceivable to me, in terms of both dimension and the shortage of reasoning that established such requirements.

A technologist would first determine what is required for positioning accuracy instead of shooting for an unnecessarily high level by addressing non-vital PTC’s weakest component, the braking algorithm. That algorithm is subject to variables that often are not even known as to value, yet alone their coefficients, i.e., braking system condition at any one point; actual consist weight, especially for long trains; and rail condition, such as the presence of wet leaves. The topography confronting the train is known, but the above variables can overwhelm the positioning module accuracy. In other words, accuracy requirement is in terms multiple meters, not centimeters. Arguing that such accuracy is required for track determination in parallel track configurations demonstrates a lack of understanding about PTC. For example, a switch position monitoring method I designed for dark territory and track circuits in CTC has that covered.

Consider this extract from the December article: “One technology that needs to be considered is the use of additional satellite arrays and frequency bands provided by the Global Navigation Satellite System (GNSS).” A point is made about inadequacy of GPS availability in some topography. A technologist would reply on three points: 

• First, there is little need if any for greater precision, as noted above. 

• Second, such situations can be readily addressed with installation of DGPS (Differential GPS) towers. 

• Third, using the Kalman process provides reasonable accuracy for extended time situations, which can be determined by technologists.

That’s it. No other expensive expansion of satellite-positioning technologies is required. What one does, as I designed for CBTM (CSX’s PTC project), is provide a buffer zone that can be mathematically determined (Monte Carlo simulation would be ideal) within acceptable statistical limits. To be honest, for CBTM, I simply made an estimate without any real analysis at that point in its deployment. Again, PTC is not vital.

Indeed, technologists are a rare breed in traditional, primary industries. They should have a broad understanding of primary technologies. Ideally, they also have an MBA mindset with training and experience in such disciplines as to discounted cash flow, econometric modeling, linear programming, simulation modeling and statistics. I say this because I am so trained and have employed such disciplines in nearly everything I have designed, including PTC, and the VCTC (Virtual CTC) for Egypt’s and Kazakhstan’s railroads that eliminates track circuits.

Looking Ahead

I see three major pursuits for railroads, individually and collectively.

First is the use of VCTC-type systems to replace conventional CTC. The details of VCTC have been presented in earlier Railway Age articles as well as on my blog, strategicrailroading.com. Simply stated, it is the use of GPS on both the head and rear end of a train to determine block occupancy, eliminating the need for nearly all CTC wayside infrastructure.

Second, each railroad needs to perform an EITA (Enterprise IT Architecture) based upon Single Source of Truth (SSOT) philosophy. My consultancy has provided the first such analysis in the industry for KTZ, Kazakhstan’s railroad. Given the amount of data that can be provided via the Internet and a wireless data network, EITA can best-provide manageable and reliable design of a railroad’s IT architecture. This is not a simple effort. As a consultant to KTZ, I was provided a limited view of what it had done with my model. I believe that every major railroad can benefit from such an analysis. However, it requires top management’s commitment to providing the proper resources and well-experienced facilitators.

Third, the railroads collectively require an industry-based business strategy aligned with an industry-based technology strategy developed by technologists as to what can be accomplished with an industry-based EITA and the available wireless data network.

The bottom line: Suppliers and rail management need to leverage technologists to consider alternatives, cost-effective solutions for advancing the safety and efficiency of rail operations.

All of the major points noted in this article are included in Ron Lindsey’s suite of courses he offers to suppliers and railroads, at all levels of their organizations, with P.E. continuing education credits. 

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