Va. Code § 46.2-1090.1
In addition to other lights authorized by law, school buses may be equipped with flashing white or amber warning lights of types authorized by the Board of Education after consultation with the Superintendent of State Police. These warning lights shall be installed in a manner authorized by the Board after consultation with the Superintendent and shall be lighted while the bus is transporting school children 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 school children. Drivers of motor vehicles approaching school buses displaying lighted warning lights authorized in this section shall not be required to stop except as required in §§ 46.2-844 and 46.2-859.
Va. Code § 46.2-1090.1