Autonomous trains will mean more trains in operation and more safety – a feat unachievable without ultra-precise geolocation.
Geolocation is crucial to autonomous transport systems and mobility. Without it, trains and other mobile vehicles operating autonomously would be lost in their environment.
At the present time, railway tracks are divided into sections called “blocks”. Normally, only one train is allowed in a block at any one time. The exact position of a train in a block is not known. The block is protected by a block signal, and ground equipment (for example, track circuits or axle counters) is used to know whether a block is clear or occupied, i.e. whether or not there is a train in it.
In future signalling systems, trains will determine their location and speed themselves with on-board equipment and send this information in real-time to the “control tower” that manages traffic. This will be a new paradigm for rail transport and require the adoption of technologies similar to those found in the aeronautics, maritime, and military sectors.
In the future, an inertial navigation unit (INS) will determine a train’s location. These highly precise devices, which calculate a train’s position and speed by measuring its acceleration and rotation, will be paired with a GPS receiver.
This architecture will exploit the advantages of two technologies: the GPS will correct the integration drift of the INS, and when the GPS is unavailable (for example, in tunnels or dense urban environments), the INS will take over and indicate the train’s position. The INS will also replace the GPS when there is a disturbance of the latter, whether involuntary (e.g. the impact of metal roofs in stations or electromagnetic radiation from industrial activities) or voluntary (e.g. scrambling or decoys).
In the future, trains will be able to locate their position with extreme precision using this system. This will lighten the load on the current control-command functions and allow SNCF to increase traffic on its lines because the blocks will be shorter.