Ford 2011 Explorer Owner's Manual page 111

Driver Controls
Detection issues
The radar sensor has a limited field of vision. In some situations it may
not detect vehicles at all or detect a vehicle later than expected.
Detection issues can occur:
• When driving on a different line than the vehicle in front.
• With vehicles that edge into your lane. These vehicles can only be
detected once they have moved fully into your lane.
110
2011 Explorer (exp)
Owners Guide, 1st Printing
USA (fus)