Obsolescence management in rail signalling systems: concept and Markovian modelling

Obsolescence is one of the most common reasons for the premature replacement of signalling systems. One of the major reasons for obsolescence is the short lifespan of hardware/software components, which seem to be replaced with newer technologies almost on a daily basis. As a result, it is critical that line replaceable units (LRUs) or lowest level replaceable units (LLRUs) be available over the lifetime of the system and be monitored systematically. Obsolescence monitoring and detection is currently done through linear methods which have many issues due to the non-linear nature of the parameters as well as the inter-dependency of elements. The purpose of this paper is to describe the obsolescence concept in rail signalling and introduce a Markovian obsolescence detection model to avoid early system obsolescence. Normally, suppliers support their customers worldwide with obsolescence monitoring in order to obtain early information on equipment obsolescence issues. Nevertheless, to sustain effective obsolescence management, agencies should allocate adequate resources such as personnel, budget and tools. An obsolescence plan/strategy is discussed in this paper and can be applied across a system's lifecycle. Such an obsolescence plan should be backed up by supply chain strategy during the system lifecycle in conjunction with asset management.