La. Roads, Bridges and Ferries § 48:947
All tolls and revenues collected under the provisions of this Part shall be kept by the State Treasurer in separate accounts for each bridge. The tolls and revenues derived from each bridge shall be used exclusively for its maintenance and operation, and the residue for the retirement of its bonds.
However, whenever it is necessary in the opinion of the department of highways to construct more than one bridge and approaches on a through or main highway, bonds may be issued to cover the cost of constructing the bridges and approaches and the tolls and revenues therefrom shall be kept together in one account and used for the maintenance and operation of the bridges and the retirement of the bonds. In such a case, all the bridges shall remain toll bridges until the retirement in full of all the bonds.
La. Roads, Bridges and Ferries § 48:947