Cadillac 2011 STS Owner's Manual page 206

To increase the set speed in small amounts, move
the switch briefly to resume/increase. Each time
this is done, the vehicle set speed increases by
about 1.6 km/h (1 mph).
Your vehicle will not reach the set speed until the
system determines there is no vehicle in front of you.
At that point, your vehicle speed will increase to the set
speed.
If the Adaptive Cruise Control system is already
activated,
Press at the end of the lever until the lower
speed desired is reached, then release the button.
To slow down in small amounts, briefly
press . Each time this is done, the vehicle
set speed decreases by about 1.6 km/h (1 mph).
When the system detects a slower moving vehicle, it
will adjust your vehicle's speed and maintain the
following distance (gap) selected.
4-20
Use the GAP button on the steering wheel to adjust
the follow distance between your vehicle and other
vehicle's.
Press the top of the button to increase the distance or
the bottom of the button to decrease the distance. The
first button press shows the current follow distance
setting on the HUD. The current following distance
setting is maintained until it is changed.
There are six follow distances to choose from. The
follow distance selection ranges from near to far
(one second to two seconds follow time). The distance
maintained for a selected follow distance varies based
on vehicle speed. The faster the vehicle speed the
further back you will follow. Consider traffic and weather
conditions when selecting the follow distance.