Sts. & Hy. Code, § 109.5

Whenever the construction of any facility of the United States or any department or agency thereof, or any feature thereof, requires construction or relocation of, or other change in any state highway or bridge, the department may enter into an agreement with the United States, or with the United States and any person, providing therefor, and for the exchange of any property required thereby. The department may enter into like agreements for acquisition of a right-of-way over, or respecting maintenance of, any facility, constructed or owned by the United States or any department or agency thereof, all or any portion of which is to be used for highway purposes.