In addition to other lights permitted in this article, buses operated as public carriers, taxicabs as defined in § 46.2-2000, and commercial motor vehicles as defined in § 52-8.4 may be equipped with (i) illuminated vacant or destination signs and (ii) single steady-burning white lights, emitting a diffused light of such intensity as not to project a glaring or dazzling light, for the nighttime illumination of exterior advertising. In addition to other lights authorized by this article, buses operated as public carriers may be equipped with flashing white warning lights of types authorized by the Superintendent of State Police. These warning lights shall be installed in a manner authorized by the Superintendent and shall be lighted while the bus is transporting passengers during periods of reduced visibility caused by atmospheric conditions other than darkness. These warning lights may also be lighted at other times while the bus is transporting passengers.