The Secretary of Highways, upon acquiring any such toll bridge, is hereby directed to continue the collection of tolls and charges on such bridge or bridges or reconstructed bridges until the Commonwealth has been reimbursed to the full extent of the original cost of acquiring such bridge, together with such interest thereon as shall have been expended by the Commonwealth and the cost of compensation of toll collectors and the cost of any insurance procured for such bridge. All tolls and charges collected by the Secretary of Highways shall be paid into the Toll Bridge Fund and the salaries of toll collectors and any insurance premiums shall be paid therefrom, on requisition of the Secretary of Highways. Whenever the tolls collected from such bridge, after deduction of all moneys expended for the cost of compensation of toll collectors and costs of insurance, shall have become sufficient to reimburse the Commonwealth in full for the cost of acquiring such bridge with interest thereon, as aforesaid, then such bridge shall become and be thereafter a free bridge: Provided, however, That any such bridge shall be maintained as a free bridge and the collection of tolls thereon shall cease if at any time the legislature shall provide for the payment out of the General Fund or from the Motor License Fund, if authorized by constitutional amendment, of all interest and sinking fund charges of any bonds issued for the acquisition of such bridge. The Secretary of Highways is hereby authorized to adjust, readjust and fix, from time to time, the amount of tolls and charges on such bridge as may be acquired under the provisions of this act,¹ for the purpose of paying the interest and sinking fund charges on bonds issued for the purpose of acquisition.