(a) It shall be the duty of the department to maintain all overpasses involving railroads on the state highway system.

(b) It shall be the duty of the county or the municipality to maintain at its own expense the drainage, surface, pavement, approaches, and guardrails of all overpasses involving railroads on its respective public road system. It shall be the duty of the railroad involved to maintain at its own expense any floors constructed of wood and the foundations, piers, abutments, and superstructures of all overpasses on the county or municipal public road system.

(c) It shall be the duty of the railroad or railroads involved to maintain all underpasses except the lighting, drainage, and pavement of the public roads thereunder, which shall be maintained by the department, counties, or municipalities on their respective public road systems.

(d) All maintenance required by this Code section of the department shall be at the expense of the department, and all maintenance required by this Code section of the railroad shall be at the expense of such railroad, provided that the duty of maintenance imposed upon the department by this Code section shall not operate to subject the department to liability for damages resulting from any failure to maintain properly.

(e) Except as provided in subsection (b) of Code Section 32-6-195, nothing in this article shall be construed as voiding agreements executed prior to July 1, 1973.