Cal. Sts. & High. Code § 100.25

In addition to the other matters that may be covered by the agreements authorized under Section 100.2, provisions for improvements, revisions or extensions of city streets or county highways leading to or from a freeway, deemed by the department to be necessary in accommodating the freeway traffic in making proper connections between the existing system of city streets or county roads and the freeway, may be included in such agreements and the department may perform such work as a part of the freeway construction.