1.    The superintendent of public instruction, in cooperation with the director, is authorized to adopt standards and specifications applicable to lighting equipment and special warning devices, including the stop sign on a control arm specified in section 39-21-18, to be carried by schoolbuses and other vehicles transporting children to school for compensation, consistent with the provisions of this chapter, but supplemental thereto. The standards and specifications must correlate with and, so far as possible, conform to the specifications then current as approved by the society of automotive engineers.

2.    It is unlawful to operate any flashing warning signal light or the stop sign on the control arm specified in section 39-21-18 on a schoolbus except when the schoolbus is stopped on a highway for the purpose of permitting schoolchildren to board or alight from the schoolbus.

3.    Schoolbuses equipped with safety strobe lights pursuant to subsection 4 of section 39-21-18 must have the safety strobe light in operation whenever the schoolbus is being operated upon a highway for purposes of transporting children either to or from school or for a school-sanctioned activity. It is unlawful to operate a safety strobe light on a schoolbus when the schoolbus is used for any other purpose.