High speed signalling in France

Two important factors guided SNCF in its choice of high-speed line driving and signalling techniques: the higher the speed, the more difficult it is for drivers to perceive lineside signals properly; and, despite rail´s excellent safety record, human beings are more failure-prone than automatic devices. As a result of these two factors, the following principles were adopted in research into driving and signalling systems: the signalling system was to be designed so that the safety of very high speed trains would not be dependent on correct observation of lineside signals; and trains were to continue to be manually operated with drivers controlling acceleration, deceleration, coasting and braking but a speed monitoring system was to be mounted to check vehicle movement in relation to the signals displayed and intervene if necessary through sharp brake application. The author discusses these principles as applied to the South East and Northern TGV lines