Cal. Pub. Util. Code § 99320.5

If the transportation planning agency determines that the cost of an approved claim for capital expenditures for public transportation purposes, excluding highways, within a county is, together with all other approved claims to be paid from the local transportation fund of such county, in excess of the money in such fund for the fiscal year, the board of supervisors of such county shall be notified to call an election in conformity with the provisions of this article.