Outstanding bonds—Savings.
While any bonds, whether definitive, temporary, or interim, or warrants, certificates, or receipts of any denomination, with or without coupons attached heretofore issued by the state aeronautics commission, the toll bridge authority, the highway commission, or any of the other agencies whose functions are transferred to the department of transportation by RCW 47.01.031, remain outstanding, the powers and duties relating thereto of such agencies or of any official or employee thereof transferred by *RCW 47.01.111 to the department of transportation, or any powers and duties of any other state official or state agency with respect to such bonds, warrants, certificates, or receipts shall not be diminished or impaired in any manner that will adversely affect the interests and rights of the holders of such bonds, warrants, certificates, or receipts. The holder of any such bond, warrant, certificate, or receipt may by mandamus or other appropriate proceeding require the performance by the department of transportation, or other appropriate state official or agency, of any of the duties heretofore imposed upon any state department, official, or employee under the terms of any such prior bond, warrant, certificate, or receipt agreement or sale: PROVIDED, That the enumeration of such rights and remedies herein shall not be deemed to exclude the exercise or prosecution of any other rights or remedies by the holders of such bonds, warrants, certificates, or receipts.