Handicapped Placards may only be used if the person it is issued to is in the vehcile

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Handicapped placards are issued to the person, not the vehicle.  As a result, you cannot use the placard if the person to whom it is issued is not in the vehicle.  See below for more.
http://www.ncdot.gov/download/dmv/DMV_Brochure_Handicap_Placard_2010_05.pdf