ERTMS

Hybrid ERTMS/ETCS Level 3 Concept

The ERTMS is ... . Its description is available in the paper. The file is available here (theme here). An Alloy version is available here (theme here).

Operational Scenarios

Disconnected train	Connected train not reporting	Connected train not reporting rear info	Connected train fully reporting
			![](images/train_rear_pos}
Train with expired mute timer	Train with expired integrity timer	Actual train front position	Actual train rear position
Free VSS	Occupied VSS	Ambiguous VSS	Unknown VSS
			![](images/vss_jumping}
VSS with expired disconnected propagation timer	VSS with expired integrity loss propagation timer	MA assigned to a train	Jumping train info
			![](images/ttd_shadow_b_timer}
Free TTD	Occupied TTD	TTD with expired shadow timer A	TTD with expired shadow timer B
![](images/ttd_ghost_timer}	![](images/ttd_vss}
TTD with expired ghost propagation timer	VSSs comprising a TTD

Scenario 1 - Normal running of a single train with integrity confirmed by external device

Scenario 2 - Splitting of a composite train with integrity confirmed by external device

Scenario 3 - Shadow train

Scenario 4 - Start of Mission / End of Mission

Scenario 5 - Integrity lost

Scenario 6 - Connection lost and reconnect within session

Scenario 7 - Connection lost and reconnect within session with release of VSS

Scenario 8 - Sweeping, jumping and two trains in a VSS

Scenario 9 – Ghost train