The Office of Regulatory Staff, upon order of the commission, may issue six classes of certificates as are mentioned in Section 58-23-40 after application therefor has been made in writing by the owner of the vehicles upon blanks provided by the commission and after such hearing as the commission may consider proper. The commission must hear any objections by any person or corporation who may be affected by the issuance of a certificate by the Office of Regulatory Staff. The six classes of certificates shall be respectively designated certificate A, certificate B, certificate C, certificate D, certificate E, and certificate F.