Three safety inspections and a preventive maintenance inspection shall be conducted on each public school vehicle annually in accordance with Motor Vehicle Administration regulations and inspection standards. The supervisor of transportation or the Department's Chief of Pupil Transportation may require additional inspections of individual vehicles at any time. A daily preoperational check of each vehicle shall be performed each day the vehicle is operated. A post-operational check shall be conducted at the end of each trip. A school vehicle found to be mechanically unsafe shall be immediately discontinued from use until made safe and authorized to be placed in service again by the supervisor of transportation. Each local school system shall have a written procedure for conducting pre-operational and post-operational checks.