Cadillac 2007 XLR Owner's Manual page 156

There are six follow distances to choose from. The
follow distance selection ranges from near to far
(1 second to 2 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 you 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 choose to
travel at a distance farther than Adaptive Cruise
Control allows, disengage the system and
drive manually.
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A graphic on the HUD indicates the selected
follow distance. This picture shows a maximum
follow distance. The vehicles will move closer
as you select a smaller follow distance.