Positive Train Control Systems Research Articles

Putting Technology in Charge: Human and Organizational factors influencing the reliability of train operations under PTC

In 2018, US Congress passed the Rail Safety Improvement Act that required Class I railroads to install Positive Train Control systems on their tracks. On December 29, 2020, two days prior to the deadline, FRA announced that PTC is in operation on all 57,536 required railroad route miles. On September 25, 2021, Amtrak train 7 derailed near Joplin, Montana which resulted in the loss of 4 lives, 44 injuries, and over $22 million in damages. PTC, which is designed to prevent these types of accidents, was enabled and operating when accident happened. In this study, we identified performance factors that have a significant influence on the reliability of train operations under PTC. Although technical factors affect the operation, factors that arise from inadequate interaction of the subsystems or lack of alignment between organizational and human factors, and the technical system have a higher contribution to the train operations under PTC.

Prevention of End-of-Track Collisions in Passenger Terminals via Positive Train Control: Benefit-Cost Analysis and Operational Impact Assessment

End-of-track collisions at passenger terminals have raised safety concerns because of their potentially severe consequences such as infrastructure and rolling stock damage, service disruption, and even casualties. As introduced in the previous study sponsored by the U.S. Federal Railroad Administration, the implementation of Positive Train Control (PTC) systems at passenger terminal stations could potentially prevent end-of-track collisions. As the second phase of that project, this paper aims to provide a comprehensive evaluation of the proposed concept of operation via quantitatively identifying the safety benefits, incremental costs, and operational impacts associated with PTC enforcement on terminating tracks. The benefit-cost analysis indicates that the safety benefits may exceed the incremental costs over a 20-year period under specified circumstances and assumptions. In addition, the preliminary results disclose that the operational impact in PTC enforcement should be negligible, except for the rare occurrence of wayside interface unit (WIU) failure or radio failure in the Interoperable Electronic Train Management System (I-ETMS)-type PTC system that would result in a stop well short of the targeted point and potentially delay both onboard passengers and inbound/outbound trains. Both benefit-cost analysis and operational impact assessment methodologies are implemented in a decision tool that can be customized for different terminals with heterogeneous infrastructure and operational characteristics and be adapted to other transportation modes.

Improving Railway Operational Efficiency with Moving Blocks, Train Fleeting, and Alternative Single-Track Configurations

With installation of positive train control (PTC) on many U.S. rail corridors, Class I railroads may soon leverage these investments in communications network infrastructure to implement “advanced PTC” systems incorporating moving blocks. Train control with moving blocks can benefit operating strategies that dispatch fleets of multiple trains running at minimum headways. On single-track corridors with passing sidings long enough to hold multiple trains, fleeting may increase the efficiency of train meets, reduce train delay, and yield incremental capacity benefits. Alternative single-track configurations with fleet-length sidings at double the spacing of conventional single-train sidings can facilitate these operating strategies while minimizing additional track infrastructure and associated capital and maintenance costs. To investigate the operational synergies between moving blocks, fleeting, and longer but less frequent sidings, Rail Traffic Controller software is used to simulate and compare the delay performance of train operations on representative rail corridors for different combinations of fleeting strategy, train control system, siding configuration, and freight traffic composition. Operating fleets in conjunction with moving blocks produces the lowest overall train delay in specific cases of low schedule flexibility and heterogeneous traffic. With more efficient meets, moving blocks and/or fleeting primarily benefit low priority trains that typically wait for opposing traffic during train meets. Such incremental line capacity benefits have short-term financial consequences as they allow additional capital investments in double track to be deferred. Knowledge of train delay performance under moving blocks and fleeting will aid railway practitioners evaluating investments in advanced PTC systems and track infrastructure expansion.

Prevention of End-of-Track Collisions at Passenger Terminals via Positive Train Control

A series of end-of-track collisions occurred in passenger terminals because of noncompliant actions from disengaged or inattentive engineers, resulting in significant property damage and casualties. Compared with other types of accidents, end-of-track collision has received much less attention in the prior research. To narrow this knowledge gap, this paper firstly analyzes the safety statistics of end-of-track collisions, then develops a fault tree analysis to understand the causes and contributing factors of end-of-track collisions. With the objective of mitigating this type of risk, this paper discusses the potential implementation of Positive Train Control (PTC) for the passenger terminal. This paper primarily focuses on the enforcement of the two most widely implemented systems, the Advanced Civil Speed Enforcement System (ACSES) and the Interoperable Electronic Train Management System (I-ETMS). For each implementation scenario, the Concept of Operations (ConOps) is proposed that depicts high-level system characteristics for the proposed PTC system enforcement at stub-end terminals. Ongoing work is being carried out by the authors to fully evaluate the cost-effectiveness and operational impacts of enforcing PTC in terminating tracks to prevent end-of-track collisions.

Security requirement derivation by noun–verb analysis of use–misuse case relationships: a case study using positive train control

Use cases and misuse cases, respectively, state the interactions that an actor can have and a mal-actor be prevented from having with a system. The cases do not specify either the security requirements or the associated attributes that a system must possess to operate in a secure manner. We present an algorithmic, domain-independent approach rooted in verb---noun analysis of use cases and misuse cases to generate system requirements and the associated security attributes. We illustrate the utility of this general five-step method using Positive train control (PTC) (a command and control system used to navigate trains in a railway grid) as a case study. This approach allows the designer to protect against the effect of wireless vulnerabilities on the safety of PTC systems.

Risk Assessment of Positive Train Control by Using Simulation of Rare Events

The risk assessment of positive train control (PTC) presents a number of challenges that can be addressed through simulation, a common tool for analyzing large, complex stochastic systems. The combined analysis of a simulated rail system with safety models that track the propagation of human errors and equipment failures toward hazards and accidents (or their eventual safe resolution) enables the prediction of accidents and their probability of occurrence for a base case without PTC and an alternate case with PTC. Accidents are rare events, and when probabilities of rare events are estimated, efficiency is a major concern because the computer resources required for statistically reliable estimates are usually overwhelming. The problem of efficiency can be addressed through multilevel splitting, or staged simulation. The basic idea of splitting is to create separate copies of the simulation whenever it approaches the rare event. The FRA generalized train movement simulator (GTMS) integrates a rail system simulator with safety models and staged simulation to arrive at metrics of safety and risk that meet federal regulatory requirements. The simulation techniques used and a description of their implementation in the GTMS are presented. The paper concludes with a case study risk assessment that uses the GTMS of a nonvital overlay PTC system for a Class I railroad.

Positive Train Control (PTC) failure modes

Positive Train Control (PTC) systems can eliminate the consequences of collision or derailment. However, prior to the full-scale deployment of these systems, the Federal Government must conduct a regulatory review and approve the risk analysis of the PTC system performance. The objective of this review is to ensure that the operating environment after installation of the PTC system is at least as safe as the operating environment before the system installation. This paper is intended to provide researchers an understanding of PTC, the reason for its use, the regulatory requirements for the required comparative risk analysis of the PTC system, the critical failure modes that the comparative analysis must address, and future work that would facilitate the risk assessment process.

Incremental Train Control System

In 1995, GE started development of the incremental train control system (ITCS) for Amtrak to use on its Michigan corridor between Detroit and Chicago. The primary objective for ITCS was to allow Amtrak passenger trains to operate at 110 mi/h intermixed with freight traffic. To achieve this objective, the traditional wayside signal system would be enhanced with a positive train control (PTC) system to enforce the wayside signal indications (train movement authorities) and operating speed limits. Additionally, the highway-rail grade crossings had to provide the required warning time for trains operating at higher speeds than for what the crossings had originally been designed (79 mi/h). ITCS in Michigan is a fail-safe (vital) positive train control system that overlays the existing signal system for improved safety and provides a cost-effective solution for high-speed train operation. ITCS meets the requirements for PTC, a train control system recently mandated by the U.S. federal government to prevent trainto-train collisions, over-speed derailments, incursions into roadway worker zones, and movement over a misaligned track switch.

Electrical engineering in motion [From the Editor

This issue of IEEE Vehicular Technology Magazine includes four articles on communication-based signaling and positive train-control systems, four more covering aspects of wireless communications, and an invited paper on the state of the U.S. auto industry.

Modeling the NAJPTC network using NS-2

Positive Train Control (PTC) refers to microprocessor-based communication technologies that are capable of preventing train collisions, derailments, and injuries to workers operating within the railroad system. In North America, there are 11 competing PTC projects in various stages of refinement. The North American Joint Positive Train Control Project (NAJPTC) is one of those efforts, based on the Advanced Train Control System (ATCS) protocol. NAJPTC is a joint development project of the Association of American Railroads, the Federal Railroad Administration, and the Illinois Department of Transportation. In this paper, we use a network simulation system (NS-2) to model NAJPTC ATCS communications to determine the feasibility of that PTC system when overlaid onto geographic data from Google Earth, and digital elevation data from the United States Geological Survey. Our simulations were useful in observing and tracking the signal strength of a moving train, resolving packet collisions via strategic base station placement, and modeling and mitigating communication losses.

Trust-based secure Positive Train Control (PTC)

Positive Train Control (PTC) is a wireless control system ensuring railroad safety by enforcing train separation, speed enforcement, roadway worker protection and other safety functions. Due to shared trackage rights over each-other’s tracks in North America, company A’s trains must be safely operated by company B’s crew on company C’s tracks, requiring different PTC systems to securely interoperate with each other. We propose using a trust management system with certificates and over the air re-keying (OTAR) as a security framework to ensure secure interoperation. Preliminary estimates show that our solution meets timing needs of PTC.

Key management requirements for PTC operations

Positive train control (PTC) is an electronic system that enforces activities such as train separation, speed enforcement, and roadway worker protection essential to operate railroads safely and efficiently. Vehicular ad-hoc networks (VANETS) provide distributed real time communication of traffic hazards and road conditions among vehicles in a radio line of sight. Communicating PTC VANET systems offer the potential to reduce highway rail intersection (HRI) collisions by communicating train movement information to highway vehicles. For this to occur, different PTC systems must securely interoperate with each other. This outlines a PTC security framework utilizing using a certificate based trust management system and over the air re-keying (OTAR) to support interoperation.

Risk and Train Control: A Framework for Analysis

The effects of train control strategies on the risks of railroad operations are examined. Analysis of a hypothetical 1800-km (1, 200-mi) corridor identified the main factors that increase risks. Passenger traffic is the most important factor because the addition of passenger trains creates the possibility of catastrophic accidents with dozens of fatalities. Increasing the number of trains per day leads to more than proportional increases in the risks of collisions. Single-track operations are much more susceptible to collisions, whereas higher train speeds increase both the likelihood and the severity of the consequences of accidents if there is a signal overrun or a failure to obey a slow order. Positive train control (PTC) systems can reduce most, but not all, of the collisions and overspeed derailments, as improper train handling or equipment failure could still lead to accidents. Establishment of a digital communications link to the train should also allow the possibility for improved grade-crossing protection. For the hypothetical corridor, the potential benefits from improved grade-crossing protection were on the same order of magnitude as the predicted benefits from PTC systems. If new technologies are developed to detect broken rails, the digital communications link could also be used to implement immediate braking, thereby preventing some additional derailments. The risk-based approach demonstrated may provide a more complete assessment of rail risks than a methodology that estimates safety benefits based on documentation of accidents that might have been prevented if more advanced train control techniques had been in place. Risks include the possibility of catastrophic accidents, whether or not such accidents occurred recently. A causality-based methodology also allows greater flexibility in sensitivity analysis and in assessment of trends in traffic volume, traffic mix, and other factors.