Transport for New South Wales’ (TfNSW) Digital Systems Program (DSP) will transform Sydney’s rail network to create high capacity ‘turn up and go’ services to meet growing demand. It will replace legacy signalling and train control technologies, based on 1980s and earlier computer-based interlocking, with European Train Control System (ETCS), Traffic Management System (TMS) and Automatic Train Operation (ATO). The replacement of the heart of the signalling and control systems of the heavy-rail network is envisaged to take years and affect many systems across the operational railway.

Modern railways are large System of Systems, comprised of several independent and geographically dispersed constituent systems (Maier 1998), where interactions are complex and prone to system level failures affecting large portions of the network. With increasing demand due to population growth, the Sydney railway infrastructure is reaching the capability limit of the employed technology, necessitating changes to increase capacity (Transport for NSW 2012). The application of digital technology promises to improve capacity, reliability and limit the effect of failures (Royal Academy of Engineering 2016) on Sydney’s railway. Systems Engineering has been adopted, early in the system lifecycle, to manage the complexity and risks in a rigorous and consistent manner.

This paper was prepared to share our insights at the 30th Annual INCOSE International Symposium, July 2020. It documents the real-life application of a Model-Based Systems Engineering (MBSE) methodology in the conceptual design stage on Transport for New South Wales’ Digital Systems Program. It illustrates how this methodology was applied to capture the operational and maintenance concepts, derive the architecture and interfaces and guide resulting requirements. We share valuable lessons-learnt for the acquiring organisation on the deployment of MBSE and its benefits.

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