Cadillac 2004 XLR - Manual (Page 131)

ACC may detect a vehicle that is not in your lane and
apply the brakes.
ACC may occasionally provide a driver alert and/or
braking that you consider unnecessary. ACC could
respond to signs, guardrails and other stationary objects
when entering or exiting a curve. This is normal
operation. Your vehicle does not need service.
Highway Exit Ramps
{ CAUTION:
ACC may lose track of the vehicle ahead and
accelerate up to your set speed while entering
or on highway exit ramps. You could be
startled by this acceleration and even lose
control of the vehicle. So, disengage ACC
before entering a highway exit ramp. Do not
use ACC on exit ramps.
3-21