§ 211. General provisions. No driver of a motor truck or motor bus shall drive such vehicle or be on duty for any period of time in excess of that authorized pursuant to regulation of the commissioner. The commissioner is hereby authorized to promulgate rules and regulations governing the hours of service of drivers of motor trucks and motor buses. Such rules and regulations shall be no less protective of public safety than the rules and regulations promulgated by the federal government with respect to hours of labor of operation of motor trucks and motor buses, provided, however, that with regard to drivers of motor buses operated by a public transportation authority operating exclusively within its jurisdictional area, the rules and regulations of the commissioner shall provide that no driver of such motor buses shall drive more than twelve hours following eight consecutive hours off duty and no driver of such motor buses shall drive for any period after having been on duty for fifteen hours following eight consecutive hours off duty and every driver of such motor buses shall have at least twenty-four consecutive hours off duty in every period of seven consecutive days and in no event shall such a driver be on duty for more than seventy-five hours in any period of seven consecutive days.