Standard features include antilock brakes, an electronic stability system, front and rear side-impact airbags, side curtain airbags and Pre-Safe. By monitoring the braking, steering and stability systems, Pre-Safe can ready occupants for a collision by tightening the seat belts, adjusting the position of the front passenger seat and available power rear seats, and closing the windows. The more advanced Pre-Safe Brake system, which requires the optional Distronic Plus adaptive cruise control system, can brake the S-Class automatically if the system deems there is a chance for an accident.