Section 146. The management and control of a transportation area shall be vested in a board of trustees of whom two shall be chosen by the mayor of each city concerned, with the approval of the city council, and two by the selectmen of each town concerned. The initial appointees shall serve for terms of one and two years, respectively, and their successors for terms of two years. If a transportation area is established by a single city, or town, its board of trustees shall consist of five members, of whom the initial appointees shall serve for one, two, three, four and five years, respectively, and their several successors for five years each. Each trustee shall be sworn to the faithful performance of his duty, and a certificate thereof shall be recorded in the records of the secretary of the area, and shall serve until his successor is qualified. A trustee may be removed for cause by the appointing authority, and any vacancy shall be filled in the same manner as an original appointment. The trustees shall not be deemed public officers within the meaning of section forty of chapter two hundred and seventy-one, nor shall they incur any personal liability as such. Together with their agents and employees, they shall be deemed agents of the transportation area. The trustees shall receive no stated salaries, but may be paid not more than ten dollars each for every meeting attended, but no trustee shall receive in the aggregate more than three hundred dollars annually. No stockholder in a street railway company the property of which is leased to a transportation area shall act as a trustee for such area.