Notwithstanding Section 454, the commission may establish a “zone of rate freedom” for any passenger stage transportation service which is operating in competition with other passenger transportation service from any means of transportation, if the competition together with the authorized zone of rate freedom will result in reasonable rates and charges for the passenger stage transportation service. An adjustment in rates or charges within a zone of rate freedom established by the commission is hereby deemed just and reasonable. The commission may, upon protest or

on its own motion, suspend any adjustment in rates or charges under this section and institute proceedings under its rules of practice and procedure.