If there are practical difficulties or unnecessary hardships for an operator to comply with the rules and regulations under this act, the commissioner, with the approval of the board, may modify the application of such rules or regulations to such a situation, if the spirit of the provisions shall be observed and the public safety is secured. Any operator may make a written request to the board stating his grounds and applying for such modification. Any authorization by the commissioner and the board shall be in writing and shall describe the conditions under which the modification is permitted. A record of all modifications shall be kept in the department and open to the public.