Acura 2011 RL Owner's Manual page 329

Limitations
ACC does not work below 25 mph
(40 km/h). It cannot bring your
vehicle to a complete stop.
ACC will not sound a beeper or
display a message on the multi-
information display to warn you of
vehicles going slower than 13 mph
(20 km/h) or vehicles that are
parked. In these cases, it is up to
you to maintain a safe distance by
using the brake pedal.
ACC may not recognize
motorcycles or other small
vehicles ahead of your vehicle.
ACC may react to vehicles beside
you or even a building beside you
by momentarily applying the
brakes or sounding a beeper under
conditions such as a sudden curve
or narrowing of the road, an
abrupt movement of the steering
wheel, or if you are in an unusual
position within your lane.
Adaptive Cruise Control (ACC)
323