FORD 2002 Expedition - Manual (Page 165)

REVERSE SENSING SYSTEM (IF EQUIPPED)
The reverse sensing system (RSS) sounds a tone to warn the driver of
obstacles near the rear bumper when the reverse gear is selected.
To help avoid personal injury, please read and understand the
limitations on the reverse sensing system described below.
Reverse sensing is only an assist for some (generally large and fixed)
objects when moving in reverse on a flat surface at “parking speeds” of
approximately 4.8 km/h (3 mph) or less. The weather may also affect
the function of RSS. RSS may have reduced performance, or be
activated in inclement weather. It is the driver’s responsibility for
ensuring that their path is clear when operating the vehicle.
To help avoid personal injury, always use caution when in
reverse and when using the reverse sensing system.
This system is not designed to prevent contact with small or
moving objects. The system is designed to provide a warning to
assist the driver in detecting large stationary objects to avoid damaging
the vehicle. The system may not detect smaller objects, particularly
those close to the ground.
The RSS will assist the driver in detecting certain objects while the
vehicle slowly moves in reverse at speeds less than 4.8 km/h (3 mph).
The RSS is not effective at speeds greater than 4.8 km/h (3 mph) and
may not detect certain angular or moving objects.
Driving
165