The downhill speed control function helps the driver when driving down steep gradients.
Downhill speed control is activated on a downhill gradient when the selector lever is in D/S and the driver applies the foot brake. The S tronic gearbox automatically changes down to a suitable gear for the gradient. The downhill speed control function attempts to maintain the speed at which the vehicle was travelling when the foot brake was applied (subject to the laws of physics and technical drive limitations). It may be necessary to adjust the speed again using the foot brake.
Downhill speed control is deactivated as soon as the road levels out again or you press the accelerator pedal.
On vehicles with cruise control system*
Link, downhill speed control is activated when you set a cruising speed.