What does a flag on the back of a bicycle or displayed on vehicles indicate?

• The bicycle or vehicle is equipped with a tracking device.
• The bicycle or vehicle has a malfunction.
• The cyclist or driver may have impaired hearing.
  Explanation:

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  A flag displayed on the back of a bicycle or on other vehicles indicates that the bicyclist or the driver may have impaired hearing.

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• The bicycle or the vehicle is transporting hazardous material.