Mercedes-Benz SLK-Class 2013 Owners Manual - Manual (Page 191)

The warning vibration occurs earlier if:
R you approach the outer lane marking on a
bend.
R the road has very wide lanes, e.g. a
freeway.
R the system recognizes solid lane markings.
The warning vibration occurs later if:
R the road has narrow lanes.
R you cut the corner on a bend.
Driving systems
189
Driving
and
parking
Z