Cadillac 2010 DTS Owner's Manual page 185

Your vehicle will not reach the set speed until the
system determines there is not a vehicle in front of you.
At that point, your vehicle speed will increase to the
set speed.
Decreasing Set Speed While Using ACC
Press the SET– button until you reach the lower speed
desired, then release it.
To slow down in very small amounts, briefly press the
SET– button. Each time this is done, the set speed
decreases by 1 km/h (1 mph) slower.
Resuming a Set Speed
Suppose the ACC is set at a desired speed and then
the brakes are applied. This will turn off the ACC. But it
does not need to be reset.
Once the vehicle speed reaches about 40 km/h (25 mph)
or more, press the +RES button. ACC will be engaged
with the previously chosen set speed.
Selecting the Follow Distance (GAP)
When the system detects a slower moving vehicle, it will
adjust your vehicle's speed and maintain the follow
distance (gap) you select.
Use the plus and minus buttons on the steering wheel
to adjust the follow distance.
Press the plus button to increase the distance or the
minus button to decrease the distance. The first button
press shows the current follow distance setting on
the DIC. The current follow distance setting will
be 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 will vary
based on vehicle speed. The faster the vehicle speed
the further back your vehicle will follow. Consider
traffic and weather conditions when selecting the follow
distance. The range of selectable distances may not
be appropriate for all drivers and driving conditions.
If you prefer to travel at a follow distance farther than
ACC allows, disengage the system and drive manually.
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