Whenever any county has appointed a road commissioner for all road districts in the county as authorized by Section 2006, or whenever any county has adopted a county charter pursuant to Section 4 of Article XI of the California Constitution, providing for the appointment of a road commissioner as a county officer, and for the organization of a permanent road department for the construction, improvement, and maintenance of highways and bridges, the road commissioner has charge of the construction and maintenance of all county bridges in the county, under the order and direction of the board of supervisors as provided in Section 1332.