When a signaling system reaches its end of life, an overall replacement is necessary. The replacement may be in-kind but for many mass transit agencies, it is common that capacity needs will have grown significantly, and the transit agency is required to increase capacity while tackling obsolescence. Capacity and obsolescence are the primary reasons for deploying Communications Based Train Control (CBTC) technology to replace conventional trip stop and track circuit-based systems operated by New York City Transit (NYCT) or cab signaling systems operated by Baltimore Maryland Transit Administration (MTA) and the San Francisco Bay Area Rapid Transit District (BART). Resignaling projects are often refereed as brownfield train control projects. Due to the technical and commercial complexity, the quantity of stakeholders, the number of interfaces, the regulatory involvement via safety certification, the temporal and geographic scale of the project and the continual evolution of the existing system, a robust Systems Engineering (SE) process is necessary to achieve success in large signaling replacement projects. This paper describes the software tools and processes that were deployed to meet the technical, legal and commercial needs of a large signaling replacement project during the specification development phase. The processes put in place were tailored to the size and location of the team members. The paper describes the software tools, such as IBM Rational DOORS, Microsoft SharePoint Online and Office 365 which were integrated and configured to allow for collaboration while accounting for the security, commercial and legal requirements of the agency. The selection, deployment and management of these processes and tools enabled the large, complex project to succeed.

The use of using cleaner energy (zero emissions) transportation has become a key focus in the North America even within rail transportation. Within in North America the migration from Diesel to Electric Locomotives, utilizing overhead catenary systems with voltages in the 25kV range for passenger trains has become the standard. In addition, “Shared-Use Rail Corridors” have become more prevalent in North America (USA and Canada), the use of Constant Warning Time Devices (CWTD) based on a change of inductance in the rail are less reliable within Electrified railroads. With shared use track, it is understood that a difference exists between freight and passenger train speeds, resulting in the need for other methods to detect and determine the correct approach times become a priority. Implementing Computer-Based Train Control (CBTC) systems or Positive Train Control (PTC) technology can mitigate the problem if they communicate / request highway crossing activation. But in locations where PTC is not being installed or in Canada where it is not required, other methods need to be explored. This paper will review and analyze the following: 1. Review the existing systems being deployed; 2. Evaluate the deployed systems effectiveness; 3. Test and record data using various innovative technologies including: Axle counters determining speed of approaching train, acceleration (+ / −); 4. Conclusion for the integrating new axle counter technologies and existing track circuits.

Communications Based Train Control (CBTC) has matured over the last 30 years to be the premiere choice for signaling of heavy rail metros throughout the world. In the United States, CBTC has lagged behind in use for a number of reasons. This paper researches these reasons and offers a solution that can benefit both the supply community as well as the end user such that CBTC can be successfully deployed as lower cost. Interoperability as a driver for this innovation will be investigated at all levels possible for operations, management, and interfaces, providing a fully integrated system.

The highest level of automation may be achieved with traditional fixed block systems with numerous benefits. Diagnostic Data can be collected from wayside infrastructure and stored in a central depository. Diagnostics from the vehicle may also be collected, not typically in a dynamic fashion, and stored in a centralized depository. This data is not easily integrated or sequenced between the onboard and wayside. External systems are added to collect all data. This centralized system composes a Maintenance and Diagnostic Center. In addition, with CBTC systems, communication between the wayside and the vehicle include ATP information, Movement Authority, Speed Restrictions from the wayside to the vehicle and reports of train location, speed, travel direction and vehicles status. With ATO, data is also transferred between the train and wayside. Much of the vehicle reported ATO data includes vehicle and on-board controller alarms and events. This train and wayside communicated data is collected and stored in the MDC with the added benefit of being integrated between the on-board and wayside. This integrated data allows data mining to be performed to evaluate many operating aspects of the system. This presentation identifies some of the types of data collected and the analysis that may be performed on the data to identify improvements that are to be integrated in system operation, detect system components that are degrading to a point of failure to help schedule maintenance before failure and provide the capability to review events post mortem to identify the root cause of failures that occur in the system.

As the existing communication technologies which for about a decade have supported railway operations and the huge transition from conventional to modern communication-based signaling approach the extent of their performance capabilities, the railway industry strives to migrate to a proven solution aiming to support the new and diverse broadband services and reduce cost. Long Term Evolution (LTE) radio access technology has been globally accepted because of the unparalleled performance, off-the-shelf convenience, and well-developed standardization. An LTE solution, however, brings both the opportunities and challenges to a Data Communication System (DCS) underlying a Communication-Based Train Control (CBTC) system. The presented research targets one of the main LTE deployment challenges; the spectrum availability. To cope with the increasing scarcity of spectrum resources, LTE/LTE-A has envisaged an extension to the unlicensed band which is already heavily populated with incompatible legacy systems such as the immensely popular Wi-Fi networks. In this paper, a design framework is established to dimension the LTE system according to the CBTC DCS sub-system level requirements. Furthermore, the LTE/Wi-Fi coexistence performance is evaluated and studied in a train control application’s context by using a Markov chain analysis approach.

This paper focuses on the safety aspect of passenger trains approaching a terminal station with a bumper block/post. As evidenced by the recent collision of a commuter train at Hoboken terminal on September 29, 2016, the consequences of a collision with a bumper post could be catastrophic, however, railroads can take preventative measures to reduce the element of risk. Case studies obtained from the National Transportation Safety Board (NTSB) involving similar bumper block accidents are analyzed to identify any potential common denominator. The objective of this paper is to comprehensively present the various mitigation techniques that railroads can adopt to safeguard their systems against these types of accidents. Although some of the mitigation techniques presented in the paper may already be known in the industry generically, their application to specifically mitigating the hazard of bumper collisions is a novel attempt to focus systematically on this topic. Examples of mitigation techniques discussed here in include speed restricting devices, driver alerted features, bumper blocks with more impact tolerance, and organizational safety culture. The effect of newer technologies such as PTC (in USA only) and CBTC towards mitigating this hazard as well as the unique constraints presented at terminal stations is also assessed.

This paper discusses two real-world challenges faced by Communications-Based Train Control (CBTC) testing programs. a) Why is it that even after a successful complete system Factory Acceptance Test (FAT), the performance of the CBTC system during the first few months of field tests is prone to frequent failures? On some projects, it may be months between a successful FAT and the first operation in CBTC mode. b) How accurately and efficiently can the root cause of failures during the field tests be identified and how could a test program be improved to have a smooth transition from field testing to revenue service. Unlike commissioning a conventional signaling system, where after circuit break down and operation testing are completed, the system works well during revenue service, CBTC projects experience an additional round of ‘surprises’ when the system is put in service after months or years of testing [1]. This comment is valid for both new lines and signaling upgrade projects, it should be noted that signaling upgrade projects are more prone to ‘surprises’ due to the limited track access which reduces testing time. Even though the final test results prior to revenue service indicate no ‘showstoppers’, once system is placed in service, it is common to unearth major issues that impact sustainable revenue operation. Though, as it should, this often comes as a surprise to transit agencies installing CBTC for the first time, it is almost accepted as fate by most of the experienced CBTC engineers. This paper describes the tests performed prior to placing system in revenue service and analyzes some of the issues experienced. Detailed information regarding the field tests can be found in [2]. Description of possible mitigations used by CBTC suppliers and transit agencies are included, as well as likely reasons for such a predictable pattern on CBTC projects. Finally, ideas about how to continue improving the mitigation to minimize the risk of major system issues are presented.

This paper provides a unique perspective on successful brownfield railroad applications. It presents realistic challenges and solutions when applying a turnkey solution with a replacement or an overlay system. Brownfield commissioning takes place when an existing infrastructure is to upgrade to a new system with a different technology than the incumbent one. As signaling systems are getting more and more complex, it is extremely important to maintain robustness in the system design as well as project execution, such as logistics, documentation, and issue reporting. Many transportation authorities are moving from their current train control signaling system to a new system to combat obsolescence issues, to gain better system capacity, and to lower operation and maintenance costs. This paper discusses brownfield commissioning in general, and also presents specific cases in migration from a track circuit interlocking system to a Communications Based Train Control (CBTC) system. These two systems have distinct characteristics that provide opportunities of coexistence, but also introduce difficulties in mixed-mode operations.

In order to conduct rail operations safely and securely, operators need reliable train connectivity. With the advent of Intelligent Transport Systems, there are increased demands from this connectivity. This paper introduces the capabilities of 3GPP standard radio technology to meet the railway operator’s connectivity needs using a unified radio infrastructure. 3GPP is the 3rd Generation Partnership Project and provides the standards known to the public as 3G or 4G mobile telecommunications provided by the cellular phone operators. Recent developments in 3GPP standards make the technology suitable for use in both urban and mainline rail environments based on a private 4G LTE network owned and operated by the railroad agency. Since the 3GPP standard equipment ecosystem is shared by mobile operators, public safety agencies, utilities, and airports, the equipment cost is reduced compared to proprietary wireless techniques due to economies of scale. Using a dedicated radio network, all rail applications requiring wireless connectivity can traverse over a single radio infrastructure. These rail applications include: CCTV real time passenger surveillance, mission critical push-to-talk voice, train control signalling (CBTC, ETCS or PTC), train telemetry, including real-time condition-based monitoring and passenger information systems. Using Quality of Service prioritization and pre-emption inherent to the LTE radio system, the mission critical railway applications always receive priority over non-mission critical functions. The FCC has recently announced the availability of the 3.5 GHz band to the public based on spectrum sharing. Spectrum sharing could be an acceptable option for railway application, provided it was given priority for mission critical functions. Current advances in LTE radio, notably Massive MIMO (multiple input, multiple output) antenna arrays, can provide coverage in 3.5 GHz band to a distance of over 1400 yards — which is less than the typical distance between stations. this transit agency dedicated network. Alternately sharing spectrum with Firstnet 700 MHz band should be explored.

A key assumption in the process of optimized design of RF systems is the efficient transfer of power from the transmitter source to the load (i.e., the end antenna). Unless the transmitter is located directly next to the load, a transmission circuit comprised of multiple cascaded or forked segments connects one to the other. An example of such transmission network is the RF transmission chain of the Communication-Based Train Control (CBTC) trackside antenna system. The system design requirement and validation process necessitates development of means for realistic evaluation and analysis of the reflection and insertion loss values offered by the trackside RF chains of a radio-based CBTC system. The aim of this research is to present a comparative study of three different models developed to quantitatively assess reflection and insertion losses in a general multi-stage RF transmission network. To provide a more realistic and credible assessment, the comparison has been further substantiated with measurement data.

The data communications subsystem or DCS is an important element of a CBTC system which supports the wired and wireless data communications between a CBTC equipped train and the wayside elements such as zone controllers and the automatic train supervisory (ATS) system. A “brown field” environment (as opposed to “green field” environment) represents an existing transit system that is already in revenue service and is being re-signaled with a new CBTC system. Such an environment typically represent the most challenging deployment for CBTC a system as it must be installed, tested and integrated in such a manner as to not adversely impact the transit agencies’ ongoing revenue service. Usually, one of the first elements of a CBTC system to be designed and deployed is the DCS. This paper will examine some lessons learned related to the DCS design, deployment, testing and commissioning for CBTC projects in a “brown field” environment with a view to improving future CBTC projects.

There is a growing trend for transit agencies to evolve from wayside and cab-based signal systems to Communication Based Train Control (CBTC). With the complexity of CBTC, a failure of CBTC component could bring a transit system to a standstill. Implementing a secondary signal system can serve to minimize the consequences of a CBTC failure. It is paramount for a transit system to continue to operate, and axle counter technology can be a suitable candidate for use as a secondary signal system. Axle Counter technology has not been widely used in the U.S., but has been used for many years in Europe and the rest of the world. This paper will review and analysis the following: 1. Train Detection Systems; Track circuits vs. axle counters and the basic Principles of Axle Counting; check-in and check-out. 2. Implementing Electromagnetic Compatibility and the EMI standards used in European with previous testing of various axle counter systems, and the frequencies that have been selected, and the proper usage of these frequencies. 3. Testing of radiated emissions using existing guidelines and methods to analyze existing wayside and vehicle Electromagnetic Interferences (EMI), environment conditions, and the limitations of installing axle counters in an existing rail or transit system. 4. Recommendations for improving vehicle and wayside specifications and standards within the U.S. for dealing with installation of axle counter equipment and with failures and EMI emissions between railway devices.

The overall performance of a Communication-Based Train Control (CBTC) system largely depends on the performance of its Data Communication Subsystem (DCS). The DCS network in almost all CBTC commercial system products marketed in the last decade utilizes radio communications in the open ISM bands (2.4 GHz or 5.8 GHz) to establish the bi-directional data link between the central/wayside and onboard segments. To ensure a stable and sound radio communication, a key question is the number of the wayside Access Points (APs) and locations of their antennas. Radio propagation modeling aims to provide an optimal and reasonably reliable solution to the cited question. The diffraction impact of sharp corners and edges in tunnels on the radio propagation process, however, has not been accounted for in majority of models. The purpose of the present research is to incorporate the effect of diffraction coupling due to sharp edges in tunnel sections which include geometrical discontinuities such as cross-junctions and L-bends through ray-mode conversion. The proposed modeling approach offers sufficient versatility to assimilate a variety of discontinuous geometries involving sharp edges in a tunnel environment. Numerical and empirical results suggest that the model provides an accurate tool for analyzing diffraction effects of tunnel discontinuities with sharp edges on the process of radio propagation.

Communications-Based Train Control (CBTC) technology is the most advanced train control system for urban railway infrastructures. It is very different from conventional relay based signaling systems and more complex than most cab signaling systems. CBTC functions are numerous, highly complex with customized details for each project. They cannot be tested for all possible conditions at all locations. Knowledge of the CTBC system and experience with train control commissioning are keys to performing enough tests to detect most issues but permit the start of revenue service as early as possible. The testing strategy proposed by the CBTC supplier is the result of years of experience with the goal of minimizing expensive field tests while demonstrating that the system will work properly in revenue service. Despite the numerous tests performed before revenue service, it is inevitable that operating challenges will be faced during the first months of CBTC system operation. The recent Institute of Electrical and Electronics Engineers (IEEE) Std 1474.4-2011 Recommended Practice for Functional Testing of a Communications-Based Train Control System [1] provides a good description how and where CBTC functions should be tested. However, it does not describe the sequence of tests in the context of a project where CBTC is deployed on a transit property. This paper presents the sequence of field tests required to commission a CBTC system and provides insight based on experience with several CBTC projects in the last decade.

The radio-based Data Communication Subsystem (DCS) between trains and wayside is a key factor for safe and efficient operation of a Communication-Based Train control (CBTC) system. To provide means for a reliable and optimized design of the DCS RF segment, this article presents an in-depth discussion of the UHF/SHF radio propagation process in tunnels. To present a flexible and realistic radio propagation prediction model inside a tunnel environment the framework of modal analysis has been combined with the ray tracing technique and a heuristic approach has been adopted to assimilate horizontal curvatures in the tunnel geometry. The theoretical radio propagation loss predictions from the proposed model are compared to field measurements collected in Toronto subway tunnels and satisfactory agreement is observed.

Wheel detection and axle counting systems provide the basic information for track vacancy detection, for controlling level crossing systems and a range of switching tasks or trigger functions. This technology is established throughout the world for standard gauge railways and is increasingly replacing track circuits. The requirements and the framework conditions in rail-based public transportation systems do, however, differ significantly from those in the standard-gauge railway and long distance track sectors. Nevertheless, in this segment too there is a clear trend towards wheel detection and axle counting systems. New lines and projects are increasingly being equipped with modern axle counting systems due to the benefits in terms of functionality and operating costs. Nowadays even in railed public transport systems, there is a clear move from track circuit systems to wheel detection and axle counting technology.

Ethernet was commercially introduced in 1980 and standardized in 1985 as IEEE 802.3. Due to the instability and unreliability of the initial introduction, safety critical systems have been slow to adapt Ethernet technologies. It is only until the Information Age brought on by the globalization of Internet in the 1990s that network gears become more cost effective, reliable, and technically suitable. With many Ethernet technologies to pick from, selection of a suitable network topology can be challenging. This paper offers insight on the problem of the optimum choice of an Ethernet technology for the purpose of safety critical system. Example of a typical CBTC system will be given along with the key design parameters and several Ethernet technologies analyzed. Simulation models are built on the basis of the two most common Ethernet technologies to provide means of comparison, and numerical results are presented in the paper.

You have selected Communications-Based Train Control (CBTC) for your new transit line, or as an upgrade to the signaling system on your existing rail network. You look forward with anticipation to the benefits it will bring your agency in terms of capacity, safety and reliability. You plan to release your Request for Proposals to the street and then sit back and watch a pack of ravenous CBTC system suppliers pounce on it, eager to make all your signaling dreams come true. But how do you ensure consistency among the offers, to enable you to select the right system for your operation? How do you specify a system that can reasonably be delivered within your budget and schedule constraints? Should you evaluate based on capital or life cycle cost? What bid evaluation criteria should you employ? There are so many factors to consider: tried and true technology vs. cutting edge; an off-the-shelf solution vs. one customized to the exacting specifications of your Operations and Maintenance departments; the degree to which redundancy should be built into the system; readiness to integrate with other support systems, like the data communications backbone or SCADA. Is one CBTC system architecture a better fit for your property, or is it “six of one, half a dozen of the other”? This paper will address the technical components of these factors, to assist you in selecting the right technology for your CBTC deployment.

Railroads are increasingly using Communication-Based Train Control (CBTC) technology to improve service capacity and operating efficiency. CBTC is a mission-critical system under which train monitoring and train control are integrated into a single unified system through data links between vehicles, central processors, and wayside equipment. Radio over fiber technology provides a flexible and efficient solution for the Data Communication System (DCS) which needs to ensure integrity and reliability of message delivery in a transparent manner for the train control functions. A Security Device (SD) is defined as a network entity located between the railroad administration’s (the customer) trusted wired network and the non-trusted portion of the DCS network including the radio-based segment, which runs on a customized piece of hardware with a secure operating system and provides secure gateway functionality. This paper puts forward a network architecture and SD software platform design which meets the requirements of a typical CBTC system. The IPSEC protocol used by the SD for data protection renders authentication service through X.509 certificates. A network setup is put together as the proof-of-concept for the presented design proposal and performance assessment is conducted through experimental studies.

Many railroads are installing new Communications Based Train Control (CBTC) systems and replacing their relay based signaling equipment with solid state equivalents. When installing new signaling and train control equipment on a property, laboratory Electromagnetic Compatibility (EMC) testing is an important part of the qualification process. Much of the new train control equipment is designed and manufactured overseas and Commercial Off The Shelf (COTS) equipment is frequently incorporated into subsystem designs. It is, therefore, important that the railroads and system providers understand the railroad EMC requirements, and that the equipment being installed is tested to the appropriate standards in the laboratory in order to ensure that it will operate as intended in the field. The two main equipment level laboratory qualification testing standards referenced in railway signaling contract specifications are the Military Standard MIL STD-461F and the CENELEC (European Committee For Electrotechnical Standardization) Standard EN 50121 (IEC equivalent IEC 62236). Although the two standards are similar, there are some key differences that can lead to costly delays if not properly understood and addressed. This paper will provide a comparison of these two standards, including the different test methodologies, specific test procedures, and test limits.