Positive Train Control — Ready to Go?

In 1922, the Interstate Commerce Commission (ICC), predecessor agency of the Federal Railroad Administration (FRA), issued the first order under the Transportation Act of 1920 to require 49 railroads to install either a train stop or train control system on at least one division over which passenger trains operated. Since that time, using technology to keep trains apart has been a strategic public policy goal. Currently, implementation of “positive train control systems” is one of the board’s Most Wanted List of transportation safety improvements.

As microprocessor technology entered the realm of railroad signaling and train control during the 1980s, the railroad industry, through the Association of American Railroads (AAR) and the Railway Association of Canada (RAC), developed detailed, tiered specifications for implementation of an advanced train control system (ATCS) that were based on the use of a digital radio communication network and microprocessor controls. As conceived, ATCS had ambitious safety and operational goals, including the replacement of existing wayside signal systems. During the same period, the BNSF Railway Company (BNSF) worked with Rockwell International to develop and demonstrate the Advanced Railroad Electronics System (ARES), which utilized data radio links and wayside equipment similar to ATCS, but foretold the future of the general rail system by relying on a global positioning system (GPS) for train location. Although both of these systems were considered to be technical successes, they were subsequently abandoned. However, ATCS radio technology was incorporated into newer traffic control systems to support pole line elimination, and much was learned from the ATCS and ARES development efforts.

In 1994, FRA delivered to Congress a report titled, Railroad Communications and Train Control that pronounced ATCS specifications to be sound and commented favorably on ARES. The report, required by the Congress, also introduced the term “positive train control” (PTC) for the first time and used it to refer to technology that could automatically intervene to prevent train collisions, control a train’s speed and ensure that trains operate within authorized limits. During the same year, the AAR and RAC abandoned their commitment to ATCS, but two freight railroads began the first of a series of new pilot projects designed to demonstrate PTC technology using GPS (augmented or not) to locate trains.

As the 1990s proceeded, the progress of high-speed rail development in the United States became a key element of the U.S. Department of Transportation’s (DOT) Next Generation High-Speed Rail Program. Digital radio communications technologies were seen as an alternative means for the railroads to enhance safety, and at the same time meet the requirements for high-speed rail implementation at a cost significantly lower than that of existing hardwired technologies.

In September 1997, FRA asked the newly formed Railroad Safety Advisory Committee (RSAC) to establish a PTC Working Group. One of the group’s first actions was to make clear that the term PTC, even though commonly associated with highly capable microprocessor and communication-based technologies used to prevent train accidents, should be reserved for a set of safety objectives, rather than a specific technology. The working group affirmed that the three core objectives of PTC systems are to prevent train collisions, to enforce speed restrictions and to provide protection for roadway workers. In 1999, the RSAC delivered to FRA’s administrator a report titled, Implementation of Positive Train Control Systems that attempted to describe a realistic blueprint for successful deployment of the technology. (The report was appended to a letter report to the Congress filed by the administrator in May 2000.) It identified specific actions that government and industry would both need to undertake if PTC was to be deployed successfully across the nation’s rail network.

Initial Steps Toward Deployment
Amtrak made the first use of PTC technologies. Based on advice regarding requirements from FRA’s Office of Safety, and ultimately supported by a 1998 order requiring its deployment, Amtrak rolled out the Advanced Civil Speed Enforcement System (ACSES) which, coupled with the existing cab signal and automatic train control systems, provides PTC capabilities supporting train speeds of up to 150 mph. Although ACSES uses transponders to determine train location, Amtrak decided to pursue the GPS-based approach for its Incremental Train Control System (ITCS), which is deployed on its Michigan line. This system has been employed in service under an FRA waiver granted in March 2000 and has supported 90-mph service since January 2002.

On the freight side, PTC remains a technology undergoing testing and demonstration, but the overall pace of its implementation is increasing rapidly. When the 1999 RSAC report was delivered, FRA was already working with CSX Transportation (CSXT) on its Communication-Based Train Management System (CBTM) and a number of other related freight railroad projects were underway (several of which were later terminated or significantly redirected). At that time it became clear to FRA that the Class I railroads were serious, but still striving to identify reliable and properly scaled technology.

FRA’s Next Generation High-Speed Rail Program had also spearheaded a partnership with Illinois DOT and other stakeholders, including the AAR, to establish the North American Joint PTC program (NAJPTC). NAJPTC had as its central objective to effectively demonstrate and deploy a new form of PTC that could support high-speed passenger rail operations (to at least 110 mph), with the potential for moving blocks and intermingled freight traffic. While that program did not result in the deployment of a fully capable train control system on the designated corridor, it did ultimately help accelerate the development of some of the technologies used in other projects.

Regulatory Support
The appearance of advanced train control systems and the envisioned size of their implementation on U.S. passenger and freight railroads underscored the critical need for regulatory support of the PTC initiative. The prescriptive nature of existing Title 49 Code of Federal Regulations (CFR), Part 236 requirements for signal and train control systems did not support microprocessor-based PTC-type system designs and the unique newly emergent train control architectures. Responding to the need for regulations, FRA worked through the RSAC to develop Performance Standards for Processor-Based Signal and Train Control Systems, published in March 2005 and effective in June 2005. These regulations, often referred to as the “PTC rule,” grandfathered PTC systems in revenue operation prior to the effective date of the regulations, and a limited allowance was made for systems under development at the time. All other PTC systems that were not otherwise exempted were required to comply with the PTC rule.

The new regulations are unique among the current federal rail safety regulations because of the extent to which they are technology-neutral and performance-based. Prior to the new rule, the existing regulations for signal and train control systems prescribed requirements for specialized, precise and inflexible electromechanical and fixed electrical and electronic circuitry. The prescriptive regulations hindered or restricted the use of newer, more advanced train control systems using versatile, general purpose and software-controlled microprocessors. In contrast, the new rule gives the railroads and vendors significant freedom to innovate and make better use of advances in technology. The realistic assessment of operational, economic and safety benefits and costs observed during the last decade of PTC systems implementation did not allow FRA to mandate PTC implementation. Instead, FRA has encouraged the voluntary implementation of PTC technology.

Despite the relative complexity of the PTC rule, the performance-based standards are quite simple and straightforward in principle. The fundamental regulatory precept of the rule is that the new system must be at least as safe as the system it is replacing or augmenting. The railroads seeking to adopt such systems must provide a comparative risk assessment for the old and new systems as evidence that the proposed system is sufficiently safe for a particular operational environment. This requirement is applicable to both passenger and freight rail systems.

The performance-based regulations establish the conditions for revolutionary changes, as opposed to evolutionary and incremental advancements, providing an environment favorable to develop innovative and technologically advanced PTC systems.

Now, with the regulatory structure in place, FRA is supporting the development, testing and implementation of several PTC prototype systems for freight, passenger and mixed traffic lines in the Pacific Northwest, Michigan, Illinois, Alaska and on the eastern seaboard. The PTC system design concept for each of these prototype systems varies, depending on the actual operational needs of railroads and the level of sophistication of existing signaling systems. Some implementation efforts are intended to satisfy the core objectives of the PTC concept by serving as an “overlay,” while the others are approaching the level of “vital application.” The vital applications aim to replace existing signaling systems or methods of train operations and extend system functionality to include issuance of movement authority and the control of wayside equipment through digital radio communication.

The configuration of each PTC system employed also varies depending on which of the two major elements of the system — dispatch/control center or the train itself — is responsible for the major decisions regarding safe operations. Some of the prototype PTC systems are office-centric or dispatch-based systems, while the others are mobile-based or train-based systems. Each has advantages and disadvantages within the overall conceptual framework provided by the regulation.

Technical Readiness
It is not the case that PTC is readily available “off the shelf” merely because most of its electronic components already exist. Nevertheless, recent system development efforts have achieved notable successes, as well as highlighted additional areas that will require further work.

As previously noted, Amtrak has successfully implemented two architecturally distinct types of PTC systems: ACSES on the Northeast Corridor (NEC) and ITCS on trackage it owns in Michigan. In December 2006, FRA approved the Product Safety Plan (PSP) for the Electronic Train Management System (ETMS) Configuration I, which applies to non-signaled territory and single-track traffic control territory on the BNSF Railway. Although approval of the PSP indicates FRA’s confidence that ETMS is safe, deployment outside the initial test bed and equipping of additional locomotives will be needed to prove that the system’s availability and performance fully support the railroads’ operational requirements. Further, the technical framework that is required to fully support mixed passenger and freight operations needs continues to be refined. It has yet to be fully demonstrated that on lines with heavy freight traffic, the PTC systems used by major freight railroads can be successfully configured to support passenger operations.

The major remaining technical challenges associated with PTC technology implementation include achieving and documenting the proven or validated interoperability between different PTC designs chosen by railroads operating over each other’s territories (as they routinely do), the deployment of a uniform and compatible human/machine interface, and — most importantly — the effective use of radio frequency bandwidth allocated for railroad industry operations with communication protocols that fully support the reliable operation of PTC systems.

There are nine ongoing PTC projects in the United States that illustrate alternative approaches for resolving these technical challenges. The projects involve nine railroads (predominantly Class I) and are located in 16 states. The systems are operated or tested on about 2,600 track miles. These projects are at different stages of development and maturation.

The ACSES system implemented by Amtrak on the NEC is a transponder-based system that enforces civil and temporary speed restrictions and positive stops at absolute signals. It is integrated with the nine-aspect cab signaling system and automatic speed control, completing the package of all PTC functionalities. It supports safe passenger rail movements at speeds of up to 150 mph, and two freight railroads operate equipped locomotives over portions of the territory. The ITCS system, employed by Amtrak in Michigan, is a train-based PTC system that employs wireless grade crossing activation and enforcement of speed restrictions and work zone boundaries. ITCS is authorized to allow passenger trains to operate at speeds of up to 95 mph on a mixed light-density freight/passenger corridor. Amtrak is currently conducting a verification and validation of the ITCS system to increase maximum allowable speed to 110 mph. Both of these Amtrak systems were grandfathered under the PTC rule, thus relieving the need to comply with its provisions.

Of the several PTC projects undertaken by freight railroads, the most advanced, in terms of deployment, is the ETMS implemented by BNSF. ETMS is an overlay on existing methods of railroad operations. Its use is currently limited to freight operations. In December 2006, ETMS had the distinction of being the first PTC system in the United States that successfully completed the regulatory review required by 49 CFR Part 236 Subpart H. As part of the approval, FRA authorized ETMS deployment on 35 BNSF subdivisions. BNSF continues to enhance ETMS capabilities, including potential integration of Amtrak-equipped locomotives. If successful, this would allow Amtrak to provide PTC-protected passenger service when transiting BNSF territories.

The freight railroads are pursuing other additional innovative and interoperable PTC systems with potential applicability to passenger rail. CSXT continues work on its CBTM overlay and UP is developing the VTMS. When complete, VTMS will be capable of replacing existing methods of operations, providing PTC functionality in a fail-safe manner. NS has commenced work on its version of a vital PTC system called optimized train control (OTC). The Ohio Central Railroad System (OCRS) has started working on its version of PTC called Train Sentinel. The CSXT, UP and NS PTC systems are all variants or derivatives of the BNSF ETMS system, while the OCRS represents a completely different design.

In addition to the preceding, deployment of other PTC systems is being actively undertaken to support revenue passenger operations. Metra has started adaptation of the BNSF ETMS to provide overspeed enforcements. Like the BNSF system, the Metra PTC system is a safety-critical overlay on existing methods of operations.

While significant progress has been made in the technical area, there are a number of ongoing issues that, if not resolved, could adversely impact PTC deployment. Systems that have been implemented are not interoperable between railroads. Trackage rights, haulage rights, shared power agreements and joint terminal operations are extensive and service requirements demand seamless transitions from one property to another. For both passenger and freight locomotives, avoiding the additional expense of equipping each locomotive with every PTC system that could be encountered underscores the critical need for proven interoperability. Closely related to standardization of the hardware is the need to establish compatible human/machine interfaces. These interfaces are crucial to allow engineers to operate the shared PTC hardware without requiring significant additional training.

Another area requiring resolution is ensuring the effective use of the radio frequency (RF) links between PTC components. Experiences on the NAJPTC project and on ITCS in particular have highlighted the need for this. The NAJPTC project sustained difficulties in resolving communication capacity issues, which necessitated its removal from revenue rail corridor originally planned and relocation to the controlled environment of the Transportation Technology Center Inc. (TTCI) in Pueblo, Colo., for further development and testing. ITCS reliability has been slightly less than optimal, necessitating installation of a new communications infrastructure to obtain a satisfactory level of reliability.

Related to the effective use of the RF links is the Federal Communications Commission’s (FCC) re-hosting of the railroad command and control frequencies to the 160MHz range channel bandwidths from 25 kHz to 12.5 kHz, with an eventual target of 6.25 kHz. The mandatory re-hosting that is required to be completed by 2013, adds pressure and complicates the resolution of RF issues for PTC. There is, however, a positive aspect to the re-hosting issue. The conversion to narrow-band communications requires that all radio systems currently in the railroad inventory be replaced. Since all radios must be replaced anyway, it provides an opportunity for railroad locomotive owners to re-equip their fleet, and make them PTC-ready.

Finally, there is the need to demonstrate the extension of PTC technologies to combined heavy freight density and passenger service corridors. The newer PTC systems designed for application to major freight lines have neither been implemented nor tested under conditions of mixed traffic. Given the relative vulnerability of passenger trains with respect to freight trains in a collision scenario, such testing is necessary to ensure that the PTC functions will correctly operate, with associated protections provided.

FRA has a number of current ongoing research projects that provide the industry with technical and funding support in resolving immediate and long-term issues discovered during deployment. Priorities are given to those projects that enhance the accuracy, capability and reliability of the PTC technology.

Even though the NAJPTC pilot project in Illinois was terminated, FRA continues to support research efforts for the implementation of moving blocks and integration of train control functions with onboard train operation assist systems such as the New York Airbrake’s LEADER System and GE Transportation Trip Optimizer. The development of vital PTC at TTCI, as a cooperative effort between FRA and the Railroad Research Foundation (RRF), will incorporate these features. The project started in January 2007 and is scheduled to be completed in three years.

In order to improve the efficiency of PTC-equipped trains, the development of a more accurate braking algorithm is required. The braking algorithms incorporated in current PTC systems are overly conservative; trains are often stopped well short of the targets. TTCI has been contracted by FRA to develop an adaptive braking algorithm with the help of the Train Operation and Energy Simulator, a computerized train simulation program. The newly developed algorithm will adjust critical parameters for braking distance calculation. This research is scheduled for completion by the third quarter of 2008.

FRA has been actively working with the railroad industry, through the AAR Wireless Communication Committee (WCC), to address problems of insufficient throughput of the communication link that support PTC systems and other digital communication-based applications, as well as issues of transition to the narrow-band VHF radios. A joint FRA and AAR project called Higher Performance Digital Radio (HPDR) focuses on the development of a radio that can integrate the voice and digital data, and provide the necessary throughput to support all foreseeable onboard communication needs. In conjunction with that, the AAR WCC, in cooperation with FRA, supports the University of Nebraska’s development efforts to integrate Wi-Fi and WiMax broadband wireless coverage to support railroad applications. Currently, railroads and the University of Nebraska are working to resolve interoperability issues associated with the data transmission.

FRA has also funded several projects to support the development of the interoperability standard and an associated system that would comply with this standard. FRA has sponsored RRF to develop an interoperable communication-based signaling system based on the proposed American Railway Engineering and Maintenance-of-Way Association and AAR industry standards. The testing of such a system is to be completed by the end of 2008. FRA is also working with RRF on exploring the possibility of having one universal platform onboard the locomotive that would perform the functions of various PTC systems. This work is the extension of earlier work called “Eastern Platform,” a standard developed by Conrail/NS/CSXT and funded by FRA. Proposals for full-scale implementation of the Universal Onboard Platform and the HPDR have been solicited from the industry.

To provide more robust roadway worker protection, TTCI, with FRA funding, has developed a design for a portable employee in charge (EIC) terminal. The EIC can use this terminal to digitally communicate with an onboard PTC system and control train movements through a roadway work zone in a vital fashion. Additional cooperative effort is required in testing this terminal with a PTC system under revenue service.
In order to assist developers of PTC systems in performing a risk assessment for a newly developed system, FRA has funded two projects: “Generalized Train Movement Modeling” by DecisionTek, LLC and “A Practical Risk Assessment Methodology for Safety-Critical Systems” by Union Switch & Signal Inc. These efforts show promise and are currently classified as research efforts. Their use for regulatory evaluation has yet to be determined.

PTC Costs
The economics of PTC implementation have been a matter of significant debate between railroad management, railroad labor, FRA and others. Various assessments performed by individual railroads during the early stages of PTC implementation have indicated that safety benefits are a very small portion of the total benefits they expect to realize. In order to derive more precise estimates, FRA commissioned a study in 2006 on PTC costs and benefits. This congressional study assessed the probable costs associated with an enhanced PTC system that could support additional railroad business capabilities beyond the basic PTC functionality of positive train separation, speed enforcement and protection of roadway workers. The results of the study confirmed that at present, safety benefits were less than 1 percent of total benefits.

The report concluded that, while the railroads would receive some benefits from PTC due to improved railroad operational and safety efficiencies, in a highly competitive market place the majority of the benefits would accrue primarily to the shippers and general public. From the estimated total net societal benefits ranging from a low of $3.3 billion per year to a high of $7.1 billion per year, it was estimated that railroads would only receive between 2.33 percent and 11.76 percent of these benefits. It should be noted, however, that the railroads’ ability to recover costs through higher rates has improved in the past several years, so that the report’s estimates regarding allocation of societal benefits may already be somewhat dated.

There is universal agreement that the cost of implementation and deployment of PTC is significant and that the safety benefits, while important, are small in relation to the costs. Implementation costs by the railroads for just 100,000 miles of track would likely require upfront capital outlays by the railroads in excess of $2.3 billion.

It is unthinkable that PTC would be applied to freight railroads while leaving passenger trains unequipped. The inevitable implication of a PTC mandate for major railroads is that passenger service providers will need to budget for this expense.

Although regulatory support of PTC technology is in place, and a significant advancement and evolution of the technology itself has occurred, technical and financial challenges still remain, which could limit widespread deployment of interoperable PTC systems on U.S. railroads. Despite these outstanding issues, FRA believes that PTC systems are closer to being ready for deployment than ever before.

Grady C. Cothen, Jr. is the deputy associate administrator for Safety Standards in FRA’s Office of Safety. Olga K. Cataldi is a senior electronics engineer on the staff of the associate administrator for Safety. Mark W. Hartong is a senior electronics engineer on the staff of the associate administrator for Safety. Yan H. Tse is the program manager for Advanced Train Control Systems in FRA’s Office of Research and Development.

More Related Information:
Archived Article: Global Rail Safety: Equipment and Technologies
Archived Article: Maintenance Matters — Plant Inspection
Mass Transit Buyer’s Guide: Rail
Transportation Video Network: Plasser American