SBB operates the most heavily and densely used rail network in the world. Every day, between 8,000 and 9,000 trains run on SBB's network of over 3,000 kilometres, delivering some 880,000 passengers to their destinations. SBB also transports around 150,000 tonnes of freight each day by rail.

Train protection plays an important role in ensuring that passenger and freight trains run safely and on time over this busy network. 

In Switzerland, three systems are currently used for train control:

• “Integra-Signum”: This warning system alerts the locomotive driver at the distant signal when approaching a closed signal or when the speed needs to be reduced. If the driver fails to observe a stop signal, the train brakes automatically. This system operates at all the main signals on the entire rail network.
• “ZUB”: This system complements Integra-Signum by continuously monitoring the speed of the train between the distant and main signals. If the driver does not reduce speed between the signals, the brakes are applied automatically. This ensures that the train is brought to a halt before a danger point (e.g. a crossing).
• “European Train Control System (ETCS) Level 1”: This train protection system largely corresponds to the principles of "ZUB" and "Integra-Signum". It is also used with track-side signals but takes the European approach of ETCS and its basic principles. In Switzerland, ETCS Level 1 is used with the LS (Limited Supervision) specific operating mode.
• “European Train Control System (ETCS) Level 2”: With this train protection system, the movement authority, speed information and route data are displayed in the driver's cab. In-cab signalling thus makes it possible to dispense with track-side signalling apart from a few indicator panels. The train movements as well as the maximum speed for the local section, the train's maximum speed, the correct route and the direction of travel are all continuously monitored by the radio block centre.

With the network-wide deployment of ETCS Levels 1 and 2, the entire Swiss standard-gauge network can now be used interoperably, i.e. without additional national train protection systems.

At present, the ETCS Level 2 cab signalling system is used in Switzerland on lines with speeds greater than 160 km/h. This train protection system is therefore used on the new high-speed Mattstetten-Rothrist line and in the Lötschberg base tunnel. The new high-speed line has been operating with ETCS Level 2 since March 2007.

SBB is the first railway in Europe to have successfully implemented an ETCS Level 2 system in full scheduled operation with train headways of two minutes.

The ETCS Level 2 cab signalling system is also used as a train protection system in the Gotthard and Ceneri base tunnels and their access routes, as well as in Valais. Further lines are to be equipped with this system in the medium term.

There are a large number of different national train protection systems in Europe for historic reasons. For a train to be able to run from Amsterdam to Genoa, it currently still requires several different train protection systems. ETCS (European Train Control System) was developed as a European standard to harmonise technologies and promote rail transport in Europe and thereby strengthen the competitive advantage of rail transport. The large number of train control systems used in European countries is to be standardised and replaced, in terms of both technology and operations, to facilitate frequent and fast cross-border train movements throughout Europe.

With the rollout of ETCS L1 (LS) completed in 2018, Switzerland is the first country in Europe to fully meet the requirements for European interoperability. The entire conventional standard-gauge rail network in Switzerland is equipped with ETCS Level 1 Limited Supervision using the existing track-side signals and can be operated with traction units equipped with the latest version of ETCS (baseline 3).