• • I U.S. Deportment - of Tro nsportotion ··JU- 4 Federal Railroad RESEARCH RESULTS Administration FRA OFFICE OF RESEARCH, DEVELOPMENT & TECHNOLOGY

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CENTRALIZEDC T ZE INTERLOCKINGoc I G (CIXL)ex FOO 0 R M 0 VINGI G BLOCKLOCK RESE EARCHE PROJECTp OJ CT SUMMARY TTCI assessed the feasibility of the proposed From September 9, 2019, to March 8, 2021, the CIXL system in areas such as hardware, Federal Railroad Administration (FRA) software, communications, as well as Reliability, sponsored Transportation Technology Center, Availability, and Maintainability (RAM) Inc. (TTCI), to develop and analyze a concept implications [1]. The feasibility assessment for a centralized interlocking (CIXL) system that indicated that the proposed system should be supports moving block methods of train control, capable of working with the existing technology improves overall availability and maintainability, as well as improving the overall system and satisfies the needs of North American maintainability, resulting in increased system railroads. availability; however, the benefits could be marginal because no hardware simplification is This CIXL system leverages the Quasi-Moving achieved in the field. Thus, the CIXL system Block (QMB) functional architecture [2], the implementation should be analyzed on a intrinsic interlocking performed by Positive Train scenario-by-scenario basis to identify where the Control Exclusive Authorities (PTCEA), and benefits outweigh the costs. train-wayside peer-to-peer communications.

Figure 1 presents the QMB architecture with BACKGROUND CIXL. Wayside Status Messages (WSM) handle TTCI identified and researched new methods of time critical communications from wayside to train control that have the potential to enhance trains, relaxing the communication demands railway safety, reliability, and operational between the office and the field as compared to performance while leveraging Positive Train the existing centralized interlocking Control (PTC) technology. architectures. The currently implemented form of PTC

Commands-- CTC over ITCM technology, referred to here as Overlay PTC (O- - status PTC), has evolved into three new modes of train control: Enhanced Overlay PTC (EO-PTC), CAOMvmt Quasi-Moving Block (QMB), and Full Moving Authority PTCEA CAO PTCEA PTC Block (FMB). Manager BOS ITCM Alerts PTCEA BOS rollups Both the QMB and FMB concepts use the exclusive non-overlapping movement authority PTCEAs PTCEA to grant movement authority to each Statut train in the territory. Office functions manage the creation and safety validation of the PTCEAs that, because of their non-overlapping property, Figure 1. QMB Architecture with Centralized can perform core interlocking functions. Interlocking (CIXL) U.S. Department of Transportation Federal Railroad Administration RR 21-07 | April 2021

As a spin-off of TTCI’s QMB project, the creation would complement the initial findings. of the current research project was to design the The RFI requested multiple details concept of operations for a CIXL system, in about the solutions including the which the execution of the interlocking functions following: architecture, hardware, is in the office instead of through current software, communications, interfaces, wayside implementations. The motivation for this safety, maintainability, failure modes, change is the potential to leverage core provider experience, and applicability to interlocking functions that will have already been moving block train control methods. implemented in the office as part of QMB as well TTCI analyzed the information received as to eliminate redundant field interlocking in the responses and used it to generate functions. the results and conclusions of the task. 2. Perform an Inventory of Control Point OBJECTIVES (CP) Topologies and Functions. The objectives of this project were to: TTCI reviewed documentation about railroad signaling systems, especially in • Understand the status, direction, and possible applications of the technology areas related to the operations of CPs of existing solutions that implement and field interlocking. Based on this centralized interlocking review, researchers prepared a questionnaire and sent it to the • Identify the variety of configurations of Railroads part of the Advisory Group field interlocking systems in use on (AG) to gather details about those North American railroads today systems that could influence or that • Develop the CIXL system for moving must be included in the concept of a block concept operations and a high- CIXL system. level implementation/migration plan for the deployment of the system The questionnaire included questions about the size of railroad operations, • Assess the feasibility of the proposed control point topologies and functions, CIXL system concept code line systems in use, network operations and failover recovery METHODS process, and the signaling system TTCI completed the following tasks: monitoring and maintenance process.

1. Perform a Technology Survey. TTCI compiled the responses and TTCI identified existing solutions that analyzed them, as well as followed up would implement centralized interlocking with the railroads to clarify or expand the based on publicly available sources, and information in the responses. gathered and analyzed the available 3. Develop a CIXL System Concept of information from those sources. The Operations initial data analysis showed that TTCI developed a CIXL system concept additional details about the solutions of operations that included architecture, were needed for the purpose of the features, functions, failure modes, and a project. high-level implementation plan of the CIXL system. Then, TTCI issued a Request for Information (RFI) to five signaling To define the CIXL system functions, each CP function, identified in the system suppliers with a presence in inventory of the CP functions subtask, North America, to collect additional was individually analyzed to determine details about the identified solutions that

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whether it could be moved to the office The feasibility assessment indicates that the and how to provide the same proposed CIXL system is attainable both from functionality when implemented in the the hardware and software needs perspectives office. without requiring new technologies to be The high-level CIXL system developed. It also suggests that the CIXL implementation/migration plan describes communication needs should not exceed those the key tasks that need to be performed of Centralized Traffic Control (CTC) over when implementing and deploying CIXL, Interoperable Train Control Messaging (ITCM). and the different approaches that can be selected by a railroad, based on its The qualitative RAM analysis concluded that, specific needs. even though the proposed CIXL solution can 4. Develop a CIXL Feasibility simplify CP software and very likely improve the Assessment. maintainability of system components, resulting TTCI assessed the feasibility of the in overall higher system availability, the proposed CIXL concept. The analysis improvements might be marginal. No reduction included the following: whether the in CP hardware was found to be attributable to proposed concept would result in RAM the CIXL system. improvements; the communication needs of the proposed architecture; the A quantitative RAM analysis is needed to prove potential reduction in costs due to field or discard the benefits of the proposed system, hardware simplification, if any; and especially regarding maintainability of the whether current hardware and software system, since the performed qualitative analysis technologies can satisfy CIXL functional, did not provide incontestable evidence to performance, and safety needs. support or reject the significance of the benefits.

CONCLUSIONS The CIXL system implementation should be TTCI based the proposed CIXL system on the analyzed on a scenario-by-scenario basis to concept that the creation of PTCEAs are in QMB identify if the benefits outweigh the with vital interlocking functionality, which grants implementation costs. movement authority directly to trains. It also The scenarios where it is more likely that this will leverages the peer-to-peer communications occur are: between the trains and Wayside Interface Units that broadcast the status of wayside devices • Territories where future changes in track through WSM. configurations are likely. If the changes include CP configuration modifications This architecture allows a train to compare its or additions, it is less costly to PTCEA with wayside conditions and apply the implement the CIXL system while taking most restrictive condition out of the two, relaxing advantage of those required the office–wayside communication demands, as modifications. compared to conventional centralized • New signaled QMB territory or territory interlocking solutions. Researchers identified with greenfield signaling deployments. that the relaxation of office-wayside These territories are candidates for the communication demands as loose office- CIXL system since it is less costly to wayside coupling. implement the CIXL system and QMB together rather than both separately. The two main components of the CIXL system architecture are the Office Component (CIXL-O) • Territory where FMB is or will be and the Field Component (CIXL-F). implemented. These are also candidates for the CIXL system since field the CIXL system is not practical

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with FMB (i.e., fixed block track circuits ACKNOWLEDGEMENTS will be eliminated). TTCI would like to acknowledge members of Currently available centralized interlocking the Train Control, Communications, and solutions generally do not satisfy the needs of Operations (TCCO) committee for their Class I railroads in areas such as compatibility contributions in the development of the CIXL and interfacing with PTC moving block train system project. control technologies (e.g., QMB and FMB), office-wayside loose coupling design, and CONTACT standard interfaces with other office systems. Jared Withers Federal Railroad Administration The high level-implementation plan identified Office of Research, Development and that the CIXL system CPs in boundaries with Technology field interlocking territories need to include the 1200 New Jersey Avenue, SE Track Code Generation function to coordinate Washington, DC 20590 (202) 493-6362 with field CIXL system CPs and to allow trains to [email protected] have a seamless transition between territories. Additionally, it is recommended that reduced Track Code Generation functionality be retained KEYWORDS at all CPs for the benefits they provide in regard Centralized interlocking system, CIXL, to maintenance, set-up, and detection Quasi-Moving Block, QMB, Positive Train performance. Control, PTC, Communications-Based Train Control, CBTC, control point, CP, Wayside Status Messages, WSM, railroad, train REFERENCES control [1] Vieira, Paulo, A. P. (2020). Higher Reliability and Capacity Train Control. In Press. CONTACT NUMBER [2] Kindt, Joel, B. P. (2020). Quasi-Moving Block DTFR53-11-D-00008L Train Control. In Press. Task Order F000085

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