Abstract: An aerodynamic drag-reducing air deflector adapted to be mounted on a truck serving to display indicia illuminated from the rear comprising a planar clear plastic-like member on which is screened in reverse the indicia and which is formed to aerodynamic shape, said rear being further coated with a translucent coating. Another embodiment utilized for quick indicia interchangeability has a clear dome and a member carrying the indicia insertable behind the dome and easily replaced with another member with different indicia. In a further embodiment the dome may be mounted on a housing.