Cadillac 2011 DTS Owner's Manual page 180

Adaptive Cruise Control 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. Disengage
Adaptive Cruise Control before entering a
highway exit ramp. Do not use Adaptive Cruise
Control while entering or on exit ramps.
If another vehicle enters the same lane as you, ACC will
not detect the vehicle until it is completely in the lane.
Be ready to take action and apply the brakes yourself.
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How well ACC will work on hills and when towing a
trailer depends on your vehicle's speed, vehicle load,
traffic conditions and the steepness of the hills. It may
not detect a vehicle in your lane while driving on hills.
When going up steep hills, you may want to use the
accelerator pedal to maintain your vehicle's speed.
When going downhill, especially when towing a trailer,
you may want to brake to keep your speed down.
Applying the brake disengages the system. You may
choose not to use ACC on steep hills, especially when
towing a trailer.
To turn off the system, apply the brake pedal, press the
cancel button, or press the ACC button.