When Mercedes-Benz first unveiled PRE-SAFE® in 2002, the primary aim was to combat the problem of the invaluable seconds often wasted just before an accident happens. The optional PRE-SAFE® safety system can make effective use of this time. Its sensors can detect critical driving situations, such as heavy oversteer/understeer, abrupt steering manoeuvres, panic braking and emergency stops.

The PRE-SAFE® electronic system evaluates this information and can initiate preventive measures in typical critical situations to protect the vehicle occupants. The front passenger seat can be moved into a more "favourable" crash position, the side windows and sliding sunroof closed, and the front seat belts tightened using electric motors. In addition, the chambers in the side bolsters of the optional active multicontour seats[1] are filled with air, which improves lateral support in critical handling situations. This enables the sidebags to deploy their full protection potential.

Additional support is available from Brake Assist PLUS (BAS PLUS) and the optional PRE-SAFE® brake. If the system detects that the distance to the vehicle ahead is decreasing too rapidly, the PRE-SAFE® brake warns the driver using audible and visual signals. During this phase, it automatically calculates the brake pressure required to avoid a collision. If the brake pedal is depressed, the required brake pressure is applied – including emergency braking if necessary. If the driver does not react, the PRE-SAFE® brake can initiate braking autonomously – first a partial application; then, if a collision is considered unavoidable, a full brake application.