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Richard Shenton MIRSE

Reliable Data Systems

Since commercial railways began around 200 years ago, passing trains have been detected from the trackside. Now we have entered the era of train based positioning. The cost of installing, operating and maintaining track circuits and other infrastructure equipment is driving the introduction of train based alternatives. Whilst GPS is widely used for train positioning on low density lines, it cannot on its own meet the exacting requirements of train control. There is a  need for a new generation of location system which can provide continuous positioning on individual lines with high  integrity and low cost.

This paper describes the operation of VTPS (Video Train Positioning System) a cab mounted vision system providing reliable positioning at low cost. The system uses image processing technology to provide the full range of positioning requirements for the operational railway, including odometry, spot location and track discrimination. The paper details the techniques that are employed and how these are used to provide accurate results with high integrity. It describes how the individual functions are combined to provide a complete positioning capability, supporting applications such as train control, platform stopping, standstill detection and train integrity.