The concept
The parking brake is primarily intended to prevent the vehicle from rolling while parked; it brakes the rear wheels.

See also:
Capacities
...
BMW EfficientDynamics: More power, less fuel consumption
With high-performance engines, superior suspension technology and an
extremely torsion-resistant body, the new BMW 3-Series is building on its
position as the sportiest sedan in its segment. It is ...
Electronic brake-force distribution
The system controls the brake pressure in the
rear wheels to ensure stable braking behavior. ...
