On the Trail of West – East Signalling Interoperability: A Novel Proposal for an STM and an Interface Proposal for ETCS Onboard Operations on Class B Trackside Signalling Systems

ERTMS and ALSN signalling systems are two of the major signalling systems that are under operation in the world. With the introduction of technical specifications for interoperability, ERTMS promises increased passenger and freight attractiveness and seamless cross-border operation. The ERTMS specifications recognise ETCS as a Class A train protection system and other signalling systems in Europe as Class B train protection systems. The specifications further define “Specific Transmission Modules” (STMs) that enable trains with ETCS onboard to operate in railway lines that are equipped with Class B train protection systems. Although ALSN is classified as a Class B train protection system, ALSN STM is not defined yet. This paper focuses on proposing a novel ALSN STM that enables trains with ETCS onboard to operate in the countries where ALSN trackside is operational. 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.