Transmission Voie-Machine (TVM, English: track-to-train transmission) is a form of in-cab signalling originally deployed in France and used on high-speed railway lines. TVM-300 was the first version, followed by TVM-430.
TVM-300 was developed in the 1970s as part of the TGV project. At speeds of above 220 kilometres per hour, TGV trains run only on dedicated tracks designated as lignes à grande vitesse (LGV). At high-speeds it is not possible for a driver to accurately see colour-light based railway signals along the track-side. Signalling information is instead transmitted to the train and displayed as part of the train controls. The driver is shown the safe operating speed, displayed in kilometres per hour.
The 1980s-developed TVM-430 system transmits more information than traditional signalling would allow, including gradient profiles and information about the state of signalling blocks further ahead. This high degree of automation does not remove the train from driver control, although there are safeguards that can safely bring the train to a stop in the event of driver error.
Read more about Transmission Voie-Machine: Other Signalling Systems