Dodge Challenger 2018 Owner's Manual page 138

136 SAFETY
The BSM system notifies the driver of objects in the
detection zones by illuminating the BSM warning light
located in the outside mirrors in addition to sounding an
audible (chime) alert and reducing the radio volume. Refer
to "Modes Of Operation" for further information.
The BSM system monitors the detection zone from three
different entry points (side, rear, front) while driving to see
if an alert is necessary. The BSM system will issue an alert
during these types of zone entries.
Entering From The Side
Vehicles that move into your adjacent lanes from either
side of the vehicle. Side Monitoring