(1) Unless these powers are otherwise delegated by the legislature, the transportation commission is the tolling authority for the state. The tolling authority shall:

(a) Set toll rates, establish appropriate exemptions, if any, and make adjustments as conditions warrant on eligible toll facilities;

(b) Review toll collection policies, toll operations policies, and toll revenue expenditures on the eligible toll facilities and report annually on this review to the legislature.

(2) The tolling authority, in determining toll rates, shall consider the policy guidelines established in RCW 47.56.830.

(3) Unless otherwise directed by the legislature, in setting and periodically adjusting toll rates, the tolling authority must ensure that toll rates will generate revenue sufficient to:

(a) Meet the operating costs of the eligible toll facilities, including necessary maintenance, preservation, renewal, replacement, administration, and toll enforcement by public law enforcement;

(b) Meet obligations for the timely payment of debt service on bonds issued for eligible toll facilities, and any other associated financing costs including, but not limited to, required reserves, minimum debt coverage or other appropriate contingency funding, insurance, and compliance with all other financial and other covenants made by the state in the bond proceedings;

(c) Meet obligations to reimburse the motor vehicle fund for excise taxes on motor vehicle and special fuels applied to the payment of bonds issued for eligible toll facilities; and

(d) Meet any other obligations of the tolling authority to provide its proportionate share of funding contributions for any projects or operations of the eligible toll facilities.

(4) The established toll rates may include variable pricing, and should be set to optimize system performance, recognizing necessary trade-offs to generate revenue for the purposes specified in subsection (3) of this section. Tolls may vary for type of vehicle, time of day, traffic conditions, or other factors designed to improve performance of the system.

(5) In fixing and adjusting toll rates under this section, the only toll revenue to be taken into account must be toll revenue pledged to bonds that includes toll receipts, and the only debt service requirements to be taken into account must be debt service on bonds payable from and secured by toll revenue that includes toll receipts.

(6) The legislature pledges to appropriate toll revenue as necessary to carry out the purposes of this section. When the legislature has specifically identified and designated an eligible toll facility and authorized the issuance of bonds for the financing of the eligible toll facility that are payable from and secured by a pledge of toll revenue, the legislature further agrees for the benefit of the owners of outstanding bonds issued by the state for eligible toll facilities to continue in effect and not to impair or withdraw the authorization of the tolling authority to fix and adjust tolls as provided in this section. The state finance committee shall pledge the state's obligation to impose and maintain tolls, together with the application of toll revenue as described in this section, to the owners of any bonds.