Abstract: A supplemental warning apparatus for school buses which is mounted on the roof of the bus in a vertical plane spaced above the usual warning sign which is carried on the side of the bus, the warning apparatus including a display member carried by a base which display member is shiftable between a retracted position and an upright vertically extended warning position. The supplemental warning apparatus may be coupled with the warning sign assembly on the side of the school bus; the passenger door of the school bus; or may be directly operated by the driver of the bus, all to the end that a warning is given from the roof of the bus which can be seen by surrounding traffic when the view of the normal warning sign on the side of the bus is blocked by such traffic.