With a view to reducing the cost of on board positioning and speed detection equipment in train control systems using radio communications, for secondary lines, GPS positioning performance was investigated in the case where it is used in combination with MSAS (MTSAT Satellite-based Augmentation System). Results showed that it was possible when using this system to locate the vehicle on the track by using horizontal protection level, when on open track sections. Furthermore, tests carried out using only on board equipment show that it should be possible to build a system which does not rely on any ground installations.