Optimising vehicle positioning systems on automatic railways-a case study

As Prime Contractor for the Docklands Light Railway System Prime Contract, Booz-Allen and Hamilton (in joint venture with Brown and Root Projects Ltd.) was responsible for completing the design and upgrading of the new advanced signalling system, new vehicle fleet and implementing organisational change. This included the integration of the new advanced signalling system with the new vehicle fleet. As the DLR was an automatic railway system, the control and stopping accuracy of the vehicles was absolutely critical to the safe and reliable operation of the system. A major challenge for Booz-Allen was to optimise the on-board signalling control algorithm to stop the vehicles (at stations) reliably within a ±50 cm window for 99.99% of the time. An even more stringent safety target was to ensure that undetected errors in the train position control system could not accumulate so as to permit a train to stop and enable its doors beyond any station platform at a rate greater than 10^-9 per hour. Booz-Allen implemented a detailed design and test programme to optimise the vehicle control algorithm. This paper discusses the process adopted, details the design issues associated with achieving safe station stops, and presents actual test data collected throughout the test and integration programme