The City agrees that all conditions of employment in its individual operation relating to hours of work, overtime differen tials and all working conditions shall be maintained at not less than the highest minimum standards in effect at the time of the passing of this Title of the Code and the conditions of employment shall be improved wherever specific provisions for improvement are made elsewhere in this Title of the Code. It is further understood and agreed that any wages, hours or working conditions agreed to that are in excess of those established herein shall not be reduced.