Every taxicab operated under this chapter shall have a rate card setting forth the authorized rates of fares displayed in such a place as to be in view of all passengers. The authorized taxicab rate shall be determined by the city commission as the need may arise, but in no case may a holder charge rates not authorized by the city commission; and the violation of this section shall be grounds for revoking such holder's certificate. (Prior code § 22-1-4)