When talking about ERTMS, we mainly talk about two systems:
- The ETCS (European Train Control System), a train control standard, based on in-cab equipment able to supervise train movements and to stop it according to the permitted speed at each line section, along with calculation and supervision of the maximum train speed at all times. Information is received from the ETCS equipment beside the track (balises or radio) depending on the operation level. The driver’s response is continuously monitored, and if necessary the emergency brakes would be taken under control.
 | The objective of this comprehensive ATP (Automatic Train Protection System) is to constantly monitor the train speed, and compare it to the maximum values that are sent by trackside signalling. This communication that is needed between onboard and trackside will be provided by means of balises (that is what operation Level 1 will be called) or by GSM-R radio connection (operation Level 2). |
- GSM-R (Global System for Mobile Communications - Railways) is the second ERTMS system, the European radio communications standard for railway operations. Based on GSM radio technology, GSM-R uses exclusive frequency bands to communicate the train with traffic control centres, devices beside the track, etc.
ERTMS is therefore the European standard for such an ATP that achieves interoperability throughout Europe. Indeed, it allows a train equipped with an ERTMS onboard device made by any supplier to run on track sections equipped with ERTMS devices made by other suppliers. This also implies the ability for any onboard equipment installed on any train to behave in exactly the same way under the same circumstances.
ERTMS does not cover all traffic management functions.