Digital Systems – Understanding the risk and impact on Sydney’s rail network, operators and customers


Transport for NSW (TfNSW) develops and delivers an integrated transport system including roads, rail, ferries, light rail and point to point transport, as well as the planning, policy, systems and infrastructure that delivers it safely for the people of NSW. Their Digital Systems Program forms part of TfNSW wider ‘More Trains, More Services’ program. It is an integral step towards transforming Sydney’s rail network using world class technology, contributing to the performance, cost and safety benefits of the NSW Future Transport Strategy 2056.

The Digital Systems program is significant, replacing legacy signalling and train controls with European Train Control System (ETCS) Level 2 signalling, Automatic Train Operation and a Traffic Management System. It is a highly complex program, implementing new technology across a busy, operational network with many stakeholders, project inter-dependencies and constraints.

Replacing aging bespoke signalling and control with internationally standardised commercial off-the-shelf products was a potential hazard. Much of this older technology was initially applied during the rail ‘golden era’ and was now struggling to meet the demands and expectations of a thriving major metropolis of some five million people. Concurrently contracting and integrating major suppliers, and quantifying and communicating new operations and maintenance routines, added to the project complexity.


Shoal was engaged to manage the program complexity, working closely with both TfNSW staff and Digital Systems contractors. We applied Systems Engineering methodologies to develop a model and framework for Digital Systems. The framework allowed program-related information, including strategy, systems, functions and requirements, to be captured in a structured and traceable manner. The framework guided the system engineering approach through rich visualisations, to support key decision-making throughout the program lifecycle.

The process entailed modelling and validating the current, interim and future state operational scenarios with operational and technical subject matter experts. Using these scenarios, a detailed impact assessment was then performed to assist with the change management process. The system boundary and external interfaces were also derived from the scenarios to clearly define the scope of Digital Systems. This enabled a consistent understanding of the system boundary and scope of Digital Systems, together with a clear grasp of the current business in terms of people, process and systems.


System and subsystem requirements were developed ensuring traceability to operational concepts, and business and stakeholder requirements. Early consideration of future state and resultant impacts was also a factor while formulating a complete and concise set of requirements.

The resulting system model captured different and complex viewpoints relating people, process and technology into one comprehensible whole. The advantage of this modelbased systems engineering approach is that changes made in the model flow seamlessly through to all generated information, ensuring information consistency across the entire program. Changes in stakeholder viewpoints, project inter-dependencies and constraints over the life of the program can be managed more effectively.

The insights gained into this complex system enabled a holistic understanding of the Digital Systems Program. It defined the links and dependencies between strategy, program business requirements, functional behaviour, architecture, system requirements, human factors and operational integration to enable TfNSW to meet their project objectives.