Dodge 2007 Durango Owner's Manual page 136

136 UNDERSTANDING THE FEATURES OF YOUR VEHICLE
If a defective bulb or wiring circuit is detected for the
turn signal system, the arrow indicators will flash at a
faster rate.
You can signal a lane change by moving the lever
partially up or down.
NOTE: If a turn signal has been left on for at least a mile
duration, a continuous chime will sound.
Turn Signal Lever