Cadillac 2005 STS Owner's Manual page 162

Other Vehicle Lane Changes
If another vehicle enters the same lane as you, Adaptive
Cruise Control will not detect the vehicle until it is
completely in the lane. Be ready to take action and apply
the brakes yourself.
Using Adaptive Cruise Controls on Hills
and When Towing a Trailer
How well Adaptive Cruise Control will work on hills and
when towing a trailer depends on your speed, vehicle
load, traffic conditions and the steepness of the hills.
3-30
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 speed. When
going downhill 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 Adaptive Cruise Control on steep hills when towing
a trailer.
Disengaging Adaptive Cruise Control
To disengage the system, apply the brake pedal or
move the Adaptive Cruise Control switch to off. Adaptive
Cruise Control information will not appear on the HUD
when the system is not engaged.
Erasing Set Speed Memory
When you turn the Adaptive Cruise Control switch or
the ignition off, the set speed memory is erased.