For a gentle descent.

Hill Descent Control (HDC).

Hill Descent Control (HDC) is a standard feature which drivers can activate when negotiating steep downhill gradients. This automatic speed control brakes each wheel individually as required, reducing the X3's forward motion to slightly more than walking speed. Drivers can vary their speed by using the accelerator or brake. This makes for a smoother, more easily controlled descent as drivers can concentrate fully on steering.