The board may investigate all means of transportation and the management thereof, the enforcement of its rules and regulations, and the action, conduct and efficiency of all officers, agents and employees of the authority. In the conduct of such investigations the board may hold public hearings on its own motion, and shall do so on complaint or petition of any municipality which has adopted this act or which has granted rights to the authority by ordinance. Each member of the board shall have power to administer oaths, and the secretary, by order of the board shall issue subpoenas to secure the attendance and testimony of witnesses, and the production of books and papers relevant to such investigations and to any hearing before the board or any member thereof or any officers’ committee or employees’ committee appointed by the board to hear any complaint of an officer or employee who has been discharged or demoted.

Any district court of this state or any judge thereof, either in term time or vacation, upon application of the board, or any member thereof, may in his or her discretion compel the attendance of witnesses, the production of books and papers, and giving of testimony before the board or before any member thereof or any officers’ committee or employees’ committee appointed by the board, by attachment for contempt or otherwise in the same manner as the production of evidence may be compelled before said court.