The author would like to thank Talgo for their support in developing this article.
The state of the art in rolling stock has evolved rather quickly in the past few years, and high speed trains are probably the most innovative of all due to the very high service quality, speed and power involved, and complex technological advances such as:
- Advanced three-phase traction motors, usually induction motors, with very high power density and almost maintenance-free, water-cooled traction converters based on semiconductors (IGBT).
- Fully redundant train control and monitoring systems – consisting of highly complex computer networks interconnecting the different vehicles and systems within the train.
- Signaling systems which support the use of Automatic Train Protection as the ERTMS (“European Rail Traffic Management System”), etc.
To illustrate the complexity, train control and monitoring systems are, from the technological point of view, quite similar to those onboard commercial jets – with the obvious differences stemming from the need to control several interconnected vehicles belonging to the same unit.
However, up to now, high-speed services rely on drivers to operate the controls fitted in the driving cab for such purposes.
So the question is: can we expect driverless operation on high-speed trains in the future?
In this analysis we have to consider that in some rail environments, such as automatic metros and people movers, driverless operation has already been achieved successfully.
ERTMS Implementation on the Spanish Infrastructure
ERTMS signaling system was introduced into the Spanish rail infrastructure in order to achieve operations with the maximum levels of safety and reliability.
ERTMS levels 1 and 2 were simultaneously deployed on tracks. The high-speed trains run on level 2, and in case of failure fall back to level 1.
In level 1, traffic management is based on telegrams sent by balises placed on fixed points along the track (figures 2-3). The antennae located under the frame of the unit’s first vehicle receives the data and a computer (EVC – European Vital Computer) processes them (figure 4).
In level 2 such functionality remains operative, however the main bulk of information is exchanged via radio by means of a train-wayside data communication system called “GSM-R,” consisting on a GSM standard specifically intended for its use on railways (figure 5).
Driving modes of AVE trains
Most AVE trains – the Spanish brand for HSR – are fitted with several selectable driving modes. For instance AVE trains of class 102, manufactured by a consortium led by Talgo, are provided with three alternative driving modes: manual, semiautomatic (preset driving speed) and automatic - usually called “automatic train operation” (ATO).
In manual and semiautomatic driving modes, the driver is responsible for choosing the driving speed.
In semiautomatic mode the driver can select a speed and the train will maintain it, applying power or brake depending on the line gradient.
In automatic mode, the driving speed is provided in real time by the ERTMS. This speed is the permitted speed, calculated by the EVC of the ERTMS, working under full supervision mode. Figure 6 shows the ERTMS display (DMI – Driver Machine Interface). The bow indicator is the permitted speed (187.5 mph or 300 km/h in the picture). The needle indicator is the real speed (184.3 mph or 295 km/h in the picture).
Safety is always guaranteed by the ERTMS, which prevents the actual speed from going over the permitted limits regardless of the driving mode being used. The ERTMS system has been designed with the maximum safety integrity level (SIL); for this purpose the value is 4, in compliance with the European standards.
For the purposes of this article, the automatic driving mode (ATO) could be a starting point for implementing an “unattended train operation” (UTO) on high speed trains.