Mercedes-Benz GL-Class 2013 Owners Manual - Manual (Page 169)

Hill start assist helps you when pulling away
forwards or in reverse on an uphill gradient.
It holds the vehicle for a short time after you
have removed your foot from the brake pedal.
This gives you enough time to move your foot
from the brake pedal to the accelerator pedal
and to depress it before the vehicle begins to
roll.
Hill start assist will not function if:
R you are pulling away on a level road or on
a downhill gradient.
R the transmission is in position N.
R the electric parking brake is applied.
R ESP ® is malfunctioning.
Driving
167
Driving
and
parking
Z