The department of transportation has the power to make all needed rules for its government and for its proceedings, and regulate the mode of all investigations and hearings of railroad companies and other parties before it, and to adopt and enforce such rules and regulations and modes of procedure as it may deem proper for the hearing and determination of all complaints made by any railroad company or other parties; provided, that no person desiring to be present at any such investigation by the department of transportation shall be denied admission.