Search

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.

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.

On August 20, 1969, two Penn Central commuter trains collided head-on near Darien, Connecticut, killing four and injuring 43. That tragedy 45 years ago began the NTSB's call for development and implementation of Positive Train Control (PTC) systems. Since then, the NTSB has issued almost 50 PTC-related safety recommendations and has included PTC on its Most Wanted List every year from its inception in 1990 until enactment of the RSIA. Unfortunately, despite some progress in the four decades since that original recommendation, PTC preventable train collisions still occur. In this paper, we identify human and organizational factors that affect a successful PTC implementation and evaluate the application of High Reliability Organizing (HRO) characteristics in the implementation of this safety system.

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.

With the latest developments in technology, the Automatic Train Operation (ATO) has been widely used in urban rail transit systems over the past decade. The control process used by the ATO system generally consists of two levels. The high-level control calculates the target speed according to the moving authority of the trains and the low-level control implements precise tracking on the target speed by controlling the traction and braking force. Most of the literature has only focused on the high-level control to optimize the train trajectory, but did not practically combine the low-level control of the ATO system. When the optimized trajectory is applied as the target speed, it will cause frequent switches between acceleration and braking for precise tracking and waste a lot of energy. Hence, this previous research may not be applied to practical ATO systems. In this paper, a numerical algorithm is proposed to solve the energy-ecient train control problem with a given trip time by distributing the reverse time to dierent segments. Then a method is presented for optimization of target speeds based on the ATO control principles, which guides the train to output optimized control sequences. The proposed approach is capable of avoiding the unnecessary switching and then eciently reduces the traction energy consumption of the train switches. Furthermore, case studies have been undertaken based on infrastructure data from the Beijing Yizhuang rail transit line, and the simulation results illustrate that the proposed approach results in good performance with regards to energy saving.

Transit service reliability, measured by such performance measures as schedule deviation and headway distribution, is a priority for transit agencies. The successful implementation of strategies to keep transit fleets as close to schedule as possible aims to improve customer service and to operate a more efficient system. Common strategies to recover time lost in day-to-day operations include switchbacks, fallbacks, route changes, and reconfigurations. The San Francisco Municipal Transportation Agency, operator of intracity bus and light rail transit in San Francisco, California, uses all of these strategies to remedy unacceptably large headway deviances. Analysis was conducted to determine the potential effects on service reliability of an application of real-time route changes of light rail vehicles at the Embarcadero turnaround. Historical advanced train control system data are applied to a calculator that reassigns the trains on the basis of average headway lengths. The calculator simulates a scenario...

Communications-based train control (CBTC) is an emerging technology for urban rail transit systems. An integrated method for assessing the capacity of CBTC-system-installed urban rail lines is proposed in this paper. Based on the UIC Code 406 method, the new integrated method includes train movement simulation, timetable construction, test and optimisation. In order to achieve an accurate blocking time, this paper introduces three operational scenarios, namely: consecutive running of trains, entering a station and turn-back at a terminal station. A practical timetable is implemented and optimised by simulating and evaluating the capacity with UIC Code 406. This paper considers Beijing’s Yizhuang metro line in a case study. It is found that a speed limit on the line produces a greater impact on the capacity compared with dwell time and switch speed restrictions. Furthermore, it is noted that a capacity bottleneck can easily occur during the process of entering a station and also during a turn-back operation at a terminal station.

This paper demonstrates an enhanced Brute Force algorithm application for optimising the driving speed curve by trading off reductions in energy usage against increases in delay penalty. A simulator is used to compare the train operation performance with different train control system configurations when implemented on a section of high-speed line operating with two trains, including differences in journey time and train energy consumption. Results are presented using six different train control system configurations combined with three different operating priorities. Analysis of the results shows that the operation performance can be improved by eliminating the interactions between trains using advanced control systems or optimal operating priorities. The algorithm is shown to achieve the objectives efficiently and accurately. Control system configurations with intermediate levels of complexity (e.g. European Train Control System Levels 2 and 1 with in-fill) when coupled with the optimisation process have been shown to have similar performance to the more advanced control system.

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.

Railroads are increasingly using new technologies to improve capacity and operating efficiency. To plan their investments and prepare for the implementation of these technologies, railroads must understand their net effect on operations. This requires understanding both the particular aspects of these technologies that affect capacity and the characteristics of the systems into which they are being introduced. Two important technologies in this regard are communications-based train control (CBTC) and electronically controlled pneumatic (ECP) brakes. Each element of CBTC and ECP brakes with the potential to affect capacity was identified, and its effect under various implementation scenarios was evaluated. The potential impact of each element was assessed and compared with the various baseline conditions and conventional technologies to understand the incremental effect. An extensive review of the literature on the subject was conducted in support of these evaluations. CBTC implementation with enforcement braking will generally result in a loss of capacity, but as these systems become more fully integrated, the potential for capacity enhancement improves. ECP brakes will provide benefits under most operational scenarios because of the shorter braking distances and thus the potential for the closer spacing of trains. The two technologies have a potential interactive effect: CBTC may make it possible to more effectively take advantage of one of the principal benefits of ECP brakes: shorter stopping distances. The results for either technology will be route and network specific, so individual railroads will need to conduct analyses to understand the net effect on the capacity of their systems.

The 2005 railroad chlorine spill in Graniteville, South Carolina, killed “only” nine people, but it illustrated the difficulties of achieving adequate capacity to handle no-notice evacuation for hazardous materials incidents. This research uses Graniteville as a case study to highlight needs for building capacity in evacuation capabilities and transportation recovery. Rail operational concepts emerged, such as the need for positive train control and automatic warning technology. The local community faced several challenges, including a lack of public understanding of how to react to a chlorine spill (even though chlorine traversed the town daily), public necessity for basic transportation to work after the evacuation, and a need for documentation of transportation infrastructure to facilitate recovery. Finally, evacuation issues arose, such as how to determine whether to shelter in place or evacuate, what routes would protect or harm people given different hazardous materials and how they behave in a spill, and the role of transportation professionals in working with emergency responders to manage evacuation. Experience and lessons learned from Graniteville can help define a national research agenda for the transportation requirements of no-notice and hazardous-materials evacuation.

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.

This analysis presents a methodology for measuring the efficiency of train dispatching as a product of three variables: (a) the type of train control system (measured by latency, defined here as the interval between occurrence of a schedule deviation and initiation of corrective action); (b) the physical capacity of the route (track kilometers per route kilometers); and (c) train minutes per route kilometer (a measure of both capacity and dispatcher competence). A mathematical relationship among these three variables is postulated, and a log-log regression analysis is used to develop coefficients that relate each of the three independent variables to dispatching efficiency. To do this, actual train-movement data and minimum train running times for 28 U.S. Class I railroad line segments are used. Results of the regression analysis indicate a statistically valid relationship among latency, track capacity, traffic volume, and dispatching effectiveness. Dispatching effectiveness, calculated by placing track kilometers per route kilometer, train minutes per route kilometer, and latency at their mean values, was 71.3 percent (the mean latency was about 17 min). At a latency of 3.5 min, average effectiveness is 81.3 percent. Examples of the trade-off between latency and effectiveness and between track capacity and effectiveness also can be calculated. For the average line, when latency is progressively reduced from the current value of 15 min to 3.5 min, dispatching effectiveness increases from 71.3 to 81.3 percent. When track kilometers per route kilometer are increased from the average value of 1.3 to 2.0 (double-tracking the entire railroad, holding all other values constant) dispatching effectiveness can be increased from 71.3 to 89.5 percent—a larger increase than that realized from a reduction in latency, but at much higher cost. To quantify the dollar benefits of such an increase in dispatching effectiveness for U.S. railroads, further analyses were carried out. Based on a previous study of Burlington Northern operations, train delay costs ranged from $163/hr to $266/hr. To simplify calculations, a value of $200/hr is used. According to U.S. railroad statistics, there are about 21 million train hours of traffic each year. Benefits available from installing communications-based train control are calculated in terms of additional train minutes per route kilometer available with an increase in dispatching effectiveness based on this analysis. Based on this analysis, it should be possible to save (1 − 0.713/0.813) or 12.3 percent of total train hours. The benefit of this would be $200 × 0.123 × 21 × 10 or $520 million annually. The Association of American Railroads has estimated the cost of positive train control for the entire U.S. railway network to be between $843 million and $1.1 billion.