Requirements for Safety Relevant Positioning Applications in Rail Traffic – A Demonstrator for a Train Borne Navigation Platform Called “DemoOrt”

Abstract

The positioning of vehicles in rail traffic plays a significant role in the system safety, since the positioning information is used for the train separation and train control. The basis for giving a route to a train is the safe track-vacancy proving. This again needs an integrity check and safe train end identification on board of the train. Therefore, the generation of positioning information is a safety relevant function. Safety critical requirements arising from the criticality of the information are accuracy, reliability, integrity and availability of the positioning information that are to be demonstrated according to the new CENELEC standards EN 50126 and 50129 with the safety integrity level 3 or 4, which are the highest levels used in the area of railways. From the operation mode of the track result further requirements, e.g. precision of positioning information of 1 to 2 metres to receive a track selective train position, or the real-time position calculation for the detection of the safe train end in the Moving Block mode. In order to make the railway transport competitive in comparison to other transport modes cost efficiency is a necessity, both in acquisition and maintenance, but also in operation. Therefore a future oriented positioning system should operate in a vehicle autonomous mode. There are several approaches to a vehicle autonomous safety relevant positioning system using GNSS, particularly the future European system Galileo with its integrity signal and diverse systems, which use different methods of measurement and determination of the position. The effects of multi-path propagation or complete shadowing and their relevance to the development of a safety relevant satellite based positioning system haven’t been taken into account in the systems investigated so far. A significant need for research has been identified in this area. From the stated requirements of the rail system and the characteristics of GNSS emanates the conclusion, that the position of a train can’t be calculated sufficiently on the basis of satellite based positioning systems alone. Hence, further data has to be included in the calculation of positioning information. The DLR’s Institute of Transportation Systems is working on the development of a demonstrator for the train borne, self-supporting navigation for safety relevant applications in the project “DemoOrt” in cooperation with the Technical University Braunschweig, the University Karlsruhe and Bombardier Transportation – Rail Control Solutions. The objective of the project “DemoOrt” is the integration of different navigation systems into an innovative platform, to demonstrate a self-supporting navigation of the rail vehicle. The harmonized concept, consisting of a GNSS-Receiver – nowadays GPS, in future the European system GALILEO, an eddy-current sensor and a digital map, performs the calculation of the positioning information with high accuracy, reliability, integrity and availability. The efficiency of the platform will be tested and demonstrated in the years 2006 and 2007 on a track near Karlsruhe in Germany and a narrow gauge line in the High Tatras in Slovakia.