The secretary, by and with the approval of the state transportation commission, may appoint some suitable person who shall be authorized to sign the name of said engineer to all vouchers as he designates from time to time in writing for the disbursement of funds. The appointee shall take the oath of office required of other employees of the department and shall execute in favor of the state a surety company bond in the sum of fifty thousand dollars ($50,000), subject to approval of the state transportation commission, conditional for the faithful performance of his duties, the premium of the bond to be paid out of the state road fund.