The levels and operation modes are fundamental concepts of the ETCS system (European Train Control System).
Level 1 involves continuous supervision of train movement (i.e. the onboard computer is continuously supervising the maximum permitted speed and calculating the braking curve to the location to which the train is permitted to proceed (the end of movement authority) while non-continuous communication occurs between train and trackside, generally through Eurobalises.
Lineside signals are necessary in level 1 applications, except if a semi-continuous infill is provided (semi-continuous infill denotes the transmission of infrastructure information from the Euroloop or the Radio infill unit to the train, hereby providing the train with information on the train’s future movement. See the Radio Infill Unit and Euroloop sections below for more information). Train detection and train integrity checks (i.e. the train is complete and has not been accidentally split) are performed by the trackside equipment beyond the scope of ERTMS.
Level 2 involves continuous supervision of train movement with constant communication via RMR between the train and trackside. The level 2 as now defined in CCS TSI 2023 merges the ETCS Level 2 and Level 3 as described in the previous CCS TSI.
Lineside signals are optional in this case, and train detection and integrity checks could be performed by the trackside equipment beyond the scope of ERTMS or managed within the scope of the ERTMS system.
The following figure shows the case of train detection and train integrity checked by the trackside equipment beyond the scope of ERTMS.
The following figure shows the case of train location and integrity managed within the scope of the ERTMS system, i.e. there is no need for lineside signals or train detection systems on the trackside other than Eurobalises. Train integrity is supervised by the train.
In addition, there are two more levels: Level 0, which applies to trains equipped with ETCS running on non-equipped lines; and Level STM, which is meant for trains equipped with ETCS running on tracks where the legacy national system (i.e. Class B system) needs to be operated. With regard to the STM level, ETCS acts as an interface between the driver and the national ATP (Automatic Train Protection).
Operation modes can be defined as different system conditions depending on the status of the trackside and the train. Unlike the ETCS levels (associated with train-trackside communication), ETCS modes are related to the operational status of the trackside or the onboard equipment.
The main ETCS modes are Full Supervision and Automatic Driving. The ETCS onboard equipment will be in Full Supervision mode when all train and track data, which is required for complete supervision of the train, are available onboard. Additionally, if ATO (Automatic Train Operation) conditions are fulfilled, the Automatic Driving mode is activated so that the train can start and stop automatically. In these modes, the onboard ETCS equipment is responsible for train protection (always ensuring that the maximum permitted speed and the end of movement authority are not exceeded).
There are also modes related to specific information that the trackside ERTMS subsystem can send, e.g. the Limited Supervision mode enables the train to be operated in areas where trackside information can be supplied to carry out background supervision of the train. In contrast to Full Supervision and Automatic Driving, in this mode, the information is simplified (especially the trackside Static Speed Profile) and the driver is responsible for the train’s movement.
There are also other modes for different operational situations. The following are some examples: shunting mode, on-sight mode (which allows the train to enter an occupied section) and a staff-responsible mode, which is a transition mode that allows train movement when it is acquiring data from the trackside under the driver’s responsibility.