The M-Class can prepare for an impact before it occurs. The standard-specification PRE-SAFE® system can trigger preventive measures in the key moments that proceed a potential accident. If the sensors register emergency braking, panic braking, abrupt steering movements at speed or heavy over/understeer, PRE-SAFE® causes the front seat belts to be pulled taut by electric motors as a precaution and the front passenger seat is moved into a position more "favourable" to a potential impact (this function is available only in conjunction with the memory package). In driving scenarios with a high level of transverse dynamics, indicating the vehicle is in imminent danger of a side-on collision or overturning, the side windows and sunroof (if fitted) can be closed automatically. When the danger has passed, the tension in the seat belts is released. All other components can then be returned to their original positions.