Power steering.

Responsive handling, precise control: the power steering system makes your BMW even more light-footed and agile, and gives you a direct, immediate driving feel. Even when parking and manoeuvring out of tight spaces, steering your BMW is effortless and direct.

A high-pressure pump, powered by the engine, builds up pressure in the system's hydraulic fluid. Lines channel the hydraulic fluid to a steering cylinder, where a control valve regulates the pressure in proportion to the movement of the steering wheel.
The cylinder is connected to the steering shaft, and the hydraulic pressure is transformed into steering force applied to the rack. Every movement of the steering wheel is noticeably lighter and easier than with unassisted steering as the system turns the front wheels in the desired direction. The steering wheel requires considerably less effort to turn, even when the vehicle is not moving.
In addition, control systems such as power steering and Active Steering adapt the amount of power assistance and/or the steering angle to suit the vehicle speed. The influence of power steering is greatest at lower speeds, and reduces gradually as speed increases.