This paper is concerned with an overview of the state-of-the-art in accurate train localisation techniques and some their applications; and describing the scope of research being carried out at the University of Birmingham, funded by the Engineering and Physical Sciences Research Council (EPSRC). The aim of our research is to identify existing and developing technologies for accurate train localisation in open space and tunnels and their applications, and attempt to match appropriate techniques, in terms of their cost and performance specifications, to the applications for different types of railway and other mass transit systems. This enables the identification of technology gaps as well as new potential applications. The study has commenced by employing systems engineering tools to build a database of techniques and applications, and to establish appropriate user requirement specifications for various types of railway operators. These tools are briefly described and their planned application to the project is outlined. The location techniques discussed include GPS, track circuits, radionavigation, and magnetic transponders.