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Peter Burns MBA, BAppSci (Elect), FIRSE, CPEng, FIEAust

PYB Consulting

As signalling technology moves from the world of the fixed signal to the world of Communication Based systems, one major issue which arises is how to deal with the legacy unfitted train.
Traditionally, the available answers to that issue have been:
    •    Don’t allow non-fitted trains to run on the relevant part of the network (the captive fleet option); or 

    •    Build the Communications based System as an overlay on traditional signalling infrastructure including its 
fixed signals. 
This second option in particular denies the railway any of the cost benefits associated with the new technology and acts as a barrier to its use. 
This paper will explore the alternative – to make the signalling for the unfitted train an overlay on the underlying Communication Based Signalling, rather than the other way around. 
The method for doing this will be explored via the example of the Electronic Virtual Trainstop. We do not have one of these right now, but we are in a position to develop its specification.


In a world where the signal engineer has involvement in defining the train’s on-board systems, this paper will explore three specific subsystems and the interfaces between them needed to achieve operability. One subsystem is part of the infrastructure, associated with the communications based signalling itself. The second is conceptually portable, but operationally part of the equipment taken on board the train. The third is the electronic virtual trainstop itself – the core on-board system. 
The issue with defining an on-board system for an unfitted train seems apparent just looking at the terms. In reality, “lack of fitment” covers a range of possibilities, ranging from no fitment whatsoever, through a very basic system-independent facility (here we find the Electronic Virtual Trainstop) to a train fully fitted with somebody else’s Communication Based signalling. Each possibility will be discussed. 
By defining the intermediate system and some basic open interfaces, the paper will show how the issue of interoperability can be managed for the full range of possible trains.