The River Tyne (Tunnels) Order 2005

9.  Where a revision of the level of tolls pursuant to paragraph 7 would be insufficient for the purposes set out in this paragraph the amount of tolls chargeable in respect of any vehicle or class of vehicles may if the undertaker so determines be increased to an amount required—

(a) to pay the costs and expenses incurred in designing, constructing, managing, operating and maintaining the tunnel crossing or any costs associated with financing any of the same;

(b) to provide such funds as are or are likely to be necessary to discharge the obligations of the undertaker pursuant to a concession agreement;

(c) to pay the interest on, and repay the principal of monies borrowed in respect of, the existing tunnels;

(d) to make payment into any maintenance or reserve fund provided in respect of the tunnel crossing; and

(e) to provide funds for, to meet expenses incurred in or the cost of securing any necessary authority or consent for, and in constructing or in securing, the construction, maintenance and operation of, the new tunnel.