Cal. Pub. Util. Code § 240302

(a) The commission, in the ordinance, shall state the nature of the tax to be imposed, the tax rate or the maximum tax rate, the purposes for which the revenue derived from the tax will be used, and shall set a term during which the tax will be imposed.
(b) The purposes for which the tax revenues may be used may include, but are not limited to, the administration of this division, including legal actions related thereto, the construction, capital acquisition, maintenance, and operation of streets, roads, highways, including state highways, and public transit systems. These purposes include expenditures for the planning, environmental reviews, engineering and design costs, and related right-of-way acquisition.
(c) The ordinance shall contain an expenditure plan which shall include the allocation of revenues for the purposes authorized by this section and shall include, at a minimum, the following provisions:
1. (1) The proportional distribution of the revenues among various purposes.
2. (2) The specific projects to be funded under the state highway and freeway portion.
3. (3) The formula for distribution of the city and county portion, which may be amended by voter approval.
(d) Following adoption of the ordinance by the voters, the expenditure plan may only be amended, if required, by the following process:
1. (1) Initiation of amendment by the commission, reciting findings of necessity.
2. (2) Approval by the board of supervisors.
3. (3) Approval by a majority of the cities constituting a majority of the incorporated population.