Subaru Forester 2020 Owner's Manual page 139

Troubleshooting
Lane Centering Function and Lane Departure Prevention Function do not operate
even though there are lane markers.
Is the width of the road too narrow or too wide?
To operate Lane Centering Function and Lane Departure Prevention Function,
the width of the road should be between approximately 10 ft (3 m) and 15 ft (4.5
m).
A lead vehicle is driving ahead of your vehicle and the lead vehicle indicator is illu-
minated, however Lane Centering Function does not activate.
Is the width of the lead vehicle too narrow?
Lane Centering Function does not activate when the lead vehicle is a motorcycle
or another 2-wheeled vehicle, super-compact car, or other narrow vehicle.
Is there a speed difference between the lead vehicle and your vehicle? Or is the
lead vehicle not directly in front of your vehicle?
Lane Centering Function may not activate in conditions such as when there is a
speed difference between the lead vehicle and your vehicle (the lead vehicle is
pulling away), or when the lead vehicle is meandering or driving at the edge of the
lane.
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