Free Ride: railway signalling at a next safety level?

Abstract

In solving harmonization and capacity problems of the future railway networks the European Rail Traffic Management System (ERTMS) is adopted as the future standard. It is intended to facilitate interoperability across borders and a more dynamic use of the railway infrastructure by separating trains based on their factual behaviour and dynamic characteristics. A gradual replacement of track bound detection and signalling by onboard detection is in progress. ERTMS applies internal instead of external information and trajectory clearance by automatic train detection and ultimately, integrity control and a moving block protection. Simultaneously, a track capacity maximizing strategy under conditions of punctuality and financial incentives for private railway operators creates goal conflicts at the operational level. Such a dual strategy of automation and coping behaviour in operational decision making creates conceptual contradictions for a safe and efficient trail control at an integral systems level. It also may erode safety principles of train separation and creates flow instability at the saturation points. Such a change in safety assurance concepts requires either a choice for an almost perfect reliable engineering design, implementation and operational strategy of full automation or a conceptual technological alternative for train control, applying a human centred design approach. This diabolic dilemma for the next development phase of ERTMS train control systems can be solved by a human centred design, the Free Ride concept.