Safe odometry for high-speed trains

The following article shows the technical reflections needed to achieve the precise speed measurements speed of trains running under ERTMS (European Rail Traffic Management System), essential to ensure the required safety level of this control-command system (not just signalling). It presents the changes in the TGV (Train à Grande Vitesse; High-speed Train) odometry: The evolution of architectures, sensors and the levels of safety depending on signalling equipment.