This driving mode is intended for an operation where the ATO function is automatically fed, in real time, by the on-board ERTMS, giving the maximum permitted speed.
The driver activates the ATO function by pressing a specific button placed on the driver’s desk (figure 7).
Additionally the driver has the freedom to set the highest allowed speed and the maximum power, by respectively setting the automatic speed control (ASC) handle and the master controller, in the desired positions; it is common to set both controllers (speed and power) to the maximum range value (figures 7-8).
The train control and monitoring system (TCMS) always takes the most restrictive speed value – the lowest one – between the speed values provided by the ERTMS and the ASC handle, and automatically calculates the tractive or braking effort required to respect such speed limit.
Unattended Train Operation (UTO)
Nowadays driverless operation has been successfully introduced in some rail environments such as metros or people movers; similar trends can be observed in other fields such as military aviation (e.g. unmanned aircraft intended for intelligence-gathering).
These experiences, along with the high degree of sophistication already in place in HSR applications, underlines the fact that we already own the required technology for driverless operation on high-speed trains, and it could be implemented provided that some changes be made on both the infrastructure and the rolling stock, as I explain below.
The existing requirements of the ERTMS do not foresee driverless operation, as concrete actions and acknowledgements are required from drivers when the train is running. ERTMS would have to be modified necessarily in order to enable driverless operation under this ATP signaling system.
Stopping at Platforms
ERTMS could bring the train to a halt at platforms by providing a maximum allowed speed of zero at the appropriate time – on a level 2 ERTMS this would be performed over the radio by the corresponding centralized traffic control (CTC). However, as the system stands nowadays, it cannot perform this action with the extremely high accuracy that would be required to stop the train in the exact place unless further changes are carried out.
The automatic metros have solved this problem by placing passive balises in the tracks near the stations, in order to let the train know its exact location as well as the precise place where the train has to stop at platforms.
Currently, the ERTMS uses position balises, but additional balises would be required for driverless operation.
Opening and Closing the Access Doors
An automatic door-unlocking system would be required when the train stopped at the stations, and passengers would then open the doors manually, as is implemented in metros and commuter trains.
The on-board access doors system would need to be informed in some way when the boarding and unboarding process has finished.
This is not easily solved using automatic systems: relying on a preset time for boarding/unboarding is simply not enough, since the associated variability for this operation is too wide in high-speed environments (e.g. very different demands depending on the particular date and time, impact of handling luggage on transfer times, etc.). A time criteria would lead to inefficiency or, even worst, unduly restricting passengers from boarding.
However such automation may not be required at all: the ticket controller could support this function by providing the “train ready to depart” signal when appropriate.
Other Aspects of High-Speed Environments
As mentioned before, high speed environments are dramatically less self-contained and controlled than those of driverless systems. Therefore, there are more factors that could impact operations, and in turn a wider variety of eventualities of a varied nature (e.g., a train stranded at an intermediate point, many miles away from the closest station).