Cal. Gov't Code § 65081.3

(a) As a part of its adoption of the regional transportation plan, the designated county transportation commission, regional transportation planning agency, or the Metropolitan Transportation Commission may designate special corridors, which may include, but are not limited to, adopted state highway routes, which, in consultation with the Department of Transportation, cities, counties, and transit operators directly impacted by the corridor, are determined to be of statewide or regional priority for long-term right-of-way preservation.
(b) Prior to designating a corridor for priority acquisition, the regional transportation planning agency shall do all of the following:
1. (1) Establish geographic boundaries for the proposed corridor.
2. (2) Complete a traffic survey, including a preliminary recommendation for transportation modal split, which generally describes the traffic and air quality impacts of the proposed corridor.
3. (3) Consider the widest feasible range of possible transportation facilities that could be located in the corridor and the major environmental impacts they may cause to assist in making the corridor more environmentally sensitive and, in the long term, a more viable site for needed transportation improvements.
(c) A designated corridor of statewide or regional priority shall be specifically considered in the certified environmental impact report completed for the adopted regional transportation plan required by the California Environmental Quality Act, which shall include a review of the environmental impacts of the possible transportation facilities which may be located in the corridor. The environmental impact report shall include a survey within the corridor boundaries to determine if there exist any of the following:
1. (1) Rare or endangered plant or animal species.
2. (2) Historical or cultural sites of major significance.
3. (3) Wetlands, vernal pools, or other naturally occurring features.
(d) The regional transportation planning agency shall designate a corridor for priority acquisition only if, after a public hearing, it finds that the range of potential transportation facilities to be located in the corridor can be constructed in a manner which will avoid or mitigate significant environmental impacts or values identified in subdivision (c), consistent with the California Environmental Quality Act and the state and federal Endangered Species Acts.
(e) Notwithstanding any other provision of this section, a corridor of statewide or regional priority may be designated as part of the regional transportation plan only if it has previously been specifically defined in the plan required pursuant to Section 134 and is consistent with the plan required pursuant to Section 135 of Title 23 of the United States Code.