Abstract :
The Northern Line of the London Underground boasts one of the world´s longest railway tunnels, upwards of 50 stations, 170 train units and typically carries over 700000 passenger-journeys per day. A major disruption in the service-a suspected fire, or a passenger falling ill-can bring the line to a halt for up to an hour, and it can take many hours thereafter to restore normal timetables. Comprehensive information to the line controllers is vital in recovering from these small disruptions and allows a more efficient use of trains and crews. Here, the authors describe positive train identification (PTI), a method of obtaining, in real time, information about the train, its crew and its destination from the most reliable source: the train driver. If there is then a discrepancy with the timetable-based arrangement held in the memory of the signal control equipment, it can be resolved before any diverging junction
