On the trail of west – east signalling interoperability:A novel proposal for an STM and an interface for ETCS onboard operating on class b trackside signalling systems

Abstract

ERTMS (European Rail Traffic Management System) and ALSN (Continuous Automatic Train Signalling) systems are two major signalling systems operating worldwide. ERTMS was presented to the world by Europe. ERTMS signalling system has specifications that aim to unify railway operations, resulting in interoperability between countries. Before publishing such specifications, European Rail Administrations dealt with different requirements and conditions, leading to inflexibility in management processes and inhomogeneous movement control systems. That is why they have proposed a set of specifications called 'Technical Specifications for Interoperability' (TSI) to enable seamless cross-border operations. The structural and functional requirements of each sub-system are provided under this directive. This dissertation will focus on TSI for "Command Control and Signalling" (CCS). The ERTMS is considered ETCS as the Class A train protection system. On the other hand, the ALSN signalling system is one of the most operational signalling systems in the world, constituting 10% of the world's railways. TSI specifications also recognise the ALSN signalling system as one of the Class B train protection systems. Every signalling system has onboard and trackside sub-systems. ERTMS has ETCS onboard and trackside sub-systems; ALSN also has ALSN onboard and trackside sub-systems. TSI specifications define interfaces and modules to allow the operation of Class A onboard signalling systems in railway lines equipped with Class B trackside systems. This kind of module is called a 'Specific Transmission Module' (STM) by the TSI specifications. This dissertation proposes a novel STM and interface to allow the operation of rolling stock with ETCS onboard a railway line equipped with an ALSN trackside signalling system. The proposed STM unit is conceptualised as a system architecture, and a new standardised interface is introduced to enable signalling interoperability between ERTMS and ALSN. A comparative literature review is performed for ERTMS and ALSN signalling systems. The study revealed that the available literature for these two systems mainly focuses on modelling, optimisation, and issues faced during implementation/ operation. Additionally, ERTMS has also STM-related literature that proves the availability of efforts for integrating other signalling systems into ERTMS. There is a huge literature gap between these two systems. According to the search query performed in Scopus, the literature of ERTMS dates back to 1968, with 2,208 articles, conference papers, books, etc. ALSN signalling system was developed in the 1930s in the Soviet Union. However, the Scopus search showed that there are only 78 registered works of literature relevant to ALSN. The major reason is that ERTMS has a set of standards and specifications that are available online to everyone around the world; however, ALSN is a closed system where no standardized approach is available with standards and specifications. The efforts for modelling the signalling systems did not get enough attention from ALSN; however, for ERTMS, new modelling techniques with different methods are proposed by various studies. The optimisation efforts in ERTMS are more focused on bringing additional features to the already well-defined sub-systems. Some studies are related to optimising one of the most vital communications in ERTMS: communication between balise and balise transmission module. For ALSN, optimisation studies are densely focused on the immunity of ALSN code and optimisation of the system itself. ERTMS literature proposes solutions for the issues raised during the transition period from legacy signalling system to ERTMS. For ALSN, these efforts are more focused on the issues raised during the operations. As defined earlier, there is a "Specific Transmission Module" (STM) that enables ETCS onboard to receive movement authority from the legacy (national) signalling system. These signalling systems might be various, as defined by the list of Class B train protection systems. There are studies that propose new STMs. The transition period from the legacy signalling system to the ERTMS signalling system is a challenging investment in technical and financial aspects. The investment is required to be made both in the trackside and onboard. New trains need to be acquired, or retrofitting of the existing stock needs to be initiated. Europe is still in the transition period, which is why new developments in STM technology are required, to realise the full potential of the existing railway. Another reason to adopt STM systems is to benefit from the competitiveness of the railway manufacturing market. Since this approach allows the operation of trains with ETCS onboard in other railway lines where a Class B signalling system is under operation, it automatically increases the capacity of the railway line, the internal return rate of the rolling stock investments and decreases the time spent in border crossings. A proposition of ALSN STM is a gateway to seamless rail transportation between the "Commonwealth of Independent States" (CIS) that connects Europe to Far Asia and South Asia. To the author's knowledge, STM for ALSN has not been proposed yet. Although Latvia, Lithuania and Estonia are part of the European Union and have the ALSN signalling system as their legacy signalling system, the attempt for an STM has not been made by those countries. Although ALSN is identified as a Class B train protection system by the interoperability technical specifications of the European Union, there is no proposed method to enable the interoperability of these two signalling systems. To perform the requirement analysis of the newly proposed STM and interface, this dissertation analyses each signalling system's working principle and sub-components. As the onboard components of ETCS are very crucial for this study, the identified components and their working principles are analysed. The ETCS onboard system has the following sub-components: Driver Machine Interface (DMI), European Vital Computer (EVC) Train Interface Unit (TIU), Balise Transmission Module (BTM), Loop Transmission Module (LTM), Euroradio, Odometry, Train Integrity and Specific Transmission Module (STM). To elaborate on the interface between onboard and trackside, more attention is paid to BTM. The responsibility of BTM is to send a tele-powering signal as a 27MHz Continuous wave signal to activate the balises and to receive the up-link signal generated by balises. The up-link signal received carries the data called "telegram" in the form of a frequency shift keying (FSK) signal. The received signal demodulates in the BTM unit to be sent to EVC. As the train passes over a balise, BTM telepowers the balise, which initiates the communication between the balise and BTM. The initiated communication results in the transfer of "Uplink data". The data processing starts in BTM, where it is demodulated to a digital telegram. BTM shares the digital telegram with European Vital Computer (EVC). In EVC, the received data is processed and displayed to train drivers on DMI. To perform the requirement analysis, ALSN trackside sub-components are identified. The most distinctive component of ALSN trackside is the code track transmitter (CTT) that generates Green (G), Yellow (Y) and Red-Yellow (RY) ALSN codes. These codes are sent to the transmitter relay (TR), where amplitude modulation occurs with a separate AC network connection. The generated codes are given to the rails with a code transformer (CT). Whenever a train enters the block section and triggers the track vacancy detection, the ALSN codes transmission window initiates. There are three types of ALSN codes: Green (G), Yellow (Y) and Red-Yellow (RY). These codes show the signal indication of the signal light that the train is approaching. Each signal aspect has a corresponding sequence of rectangular pulses with intervals. The required components are separately identified for ETCS onboard and ALSN trackside. For ETCS onboard, the required components are Driver Machine Interface (DMI), Train Interface Unit (TIU), Odometry, European Vital Computer (EVC) and Balise Transmission Module (BTM). For ALSN onboard, the required components are code track transmitter, transmitter relay DC & AC and code transformer. Additionally, the ETCS onboard shall be equipped with the newly proposed ALSN STM. ALSN STM is designed to be an external type, whereas there is no direct integration to the ETCS onboard Profibus. The requirement analysis shows that ETCS onboard shall be employed as a whole, and its integrity shall not be harmed; however, the external type ALSN STM shall be designed to result in degraded situations rather than safety hazards. As a result of the requirement analysis, the conceptual system requirements specifications of ALSN STM unit is prepared. The output of the ALSN trackside system will be the input of the ALSN STM unit. The input is AC-modulated DC impulse signals. The output of the unit is going to be the input of the ETCS trackside system. The output of ALSN STM unit will be digital telegrams that will carry the movement authority information. Since the telegram will be generated digitally by ALSN STM, the input will be directly fed into the FPGA board of the BTM unit. The AC-modulated DC impulse signals will be picked up by the receiving coils of the ALSN STM unit. The received signals will pass through the bandpass filter to eliminate the harmonics and distortions. As ALSN employs rails as a transmission medium, ALSN signals can be attenuated. Considering that the ALSN STM has an amplifier component. For demodulation, the amplified signal will go through a digital pulse converter. At this stage, the ALSN code is transformed into a movement authority. This movement authority information is sent to the conversion unit, where it performs the act of selecting the correct telegram against the received ALSN code. The matched telegram code is generated by the telegram generator and fed into the BTM unit of the ETCS onboard. This dissertation also proposes a novel interface as Conceptual Form Fit Functional Interface Specification (FFFIS). A novel interface, "E", is proposed between External ALSN STM to BTM function of ETCS onboard.