Wash. Rev. Code § 47.60.220
The department has all the obligations, duties, and rights of a common carrier of persons and property in its operation of ferries, terminals, or other facilities used in its ferry operations, including the right to participate in joint rates and through routes, agreements, and divisions of through and joint rates with railroads and other common carriers and the right to make any filings with the interstate commerce commission, the United States maritime commission, or any other state or federal regulatory or governmental body and to comply with the lawful rules and regulations or requirements of any such body, and is subject to laws relating to carrier's liability for loss or damage to property transported, and for personal injury or death of persons transported.
RCW 47.60.220