First introduced on the 7 Series, Automatic Stability Control + Traction (ASC + T) is a suspension control system that reduces engine output, until the vehicle can move or acceleration can take place, without the wheels spinning. 

This happens regardless of how the driver is using the accelerator. If the reduction in acceleration is not enough, each drive wheel is braked individually until both wheels have optimum traction. Braking is under control of the BMW pioneered Anti-lock Braking System (ABS) system.

Intelligent regulation systems prevent the vehicle from swerving when accelerating on a loose surface, insuring that directional stability is reliably maintained. If a wheel threatens to spin, the wheel brake is applied or else the system intervenes to regulate the engine management accordingly. Only so much throttle is applied to insure lateral stability, even if the accelerator is fully depressed. An integrated engine drag torque regulation system stops the drive wheels from blocking if the driver suddenly removes his foot from the accelerator. The system can be switched off if you desire.

• Optimum safety on slippery road surfaces such as ice, snow, loose gravel etc.
• Even sudden patches of slippery road surface are immediately registered and the system reacts accordingly.
• No blocking of wheels occurs, even when the accelerator is suddenly released on a slippery surface or there is a shift change to a lower gear.

ASC+T Explained also explains ABS.

ASC+T is a reprint from BMW Magazine.

ASC+T Screensaver is a penguin trying to go up a hill. The penguin is unsuccessful at many tries and falls on his back. He finally gives up and takes a BMW to go up the hill. Free download!