Streets and Highways Code § 106

Whenever in its opinion the public convenience and necessity require it for State highway purposes, the department may enter into a cooperative agreement:

(a) To construct a bridge across any river, stream, or inlet of the sea.

(b) To reconstruct or replace an existing, privately owned bridge over any river, stream or inlet of the sea, which bridge is used for highway purposes by the public and the owner.

(c) To acquire an existing bridge, or a right of way over the location of such bridge, whenever the acquisition of such bridge or right of way by the State alone would ordinarily require an excessive expenditure of State highway money.