ERTMS "in cab" works as follows:
When you enter a ERTMS section the train will "call in" to the system and will gain a "Movement authority" (to be called MA). For this the signalling system ERTMS has to know the trains length and mass.
A MA is a data package containing the distance till the END of the MA and the maximum allowed speed. Near the end of the MA the "Brake curve" will apply indicating to the driver that he has to slow down the train. Normally, and if the driver is within "brake curve limits" it will show as a yellow speedometer slowly decreasing to the desired speed at the end of the MA. When the train is not braking hard enough the speedometer will turn orange accompanied by acoustic warnings, indicating that the driver has three seconds to react. If he fails to do so the speedometer will turn red and the emergency brake will fully apply bringing the train to a complete stop.
A Movement Authority can have any specified speed limit at the end. Like a curve with a limit of 60 or a complete stop. Also the MA can be extended when the train will receive a new MA overwriting the previous one. For example the proceeding train is no longer an obstacle and a higher speed is approved.
This is what happens if a train will NOT receive a data package, or a incomplete or faulty one:
https://www.youtube.com/watch?v=3PuCN1SivXs
And during ERTMS testing: (In English)
https://www.youtube.com/watch?v=gqpYRiR6Ipc
In the Netherlands there are 4 main line routes with ERTMS:
- HSL Zuid (speeds up to 300 km/h)
- Betuweroute (Freight only)
- Amsterdam Bijlmer - Utrecht (mixed traffic, dual signalled ERTMS and classic light signals)
- Hanzelijn (Lelystad - Zwolle) (mixed traffic, dual signalled ERTMS and classic light signals)