California to Require Zero-Emissions Buses by 2040 The Golden State’s Air Resources Board voted to enforce the new requirement. The eco-friendly push will start in 2029, when the state will mandate all new buses to stop using fossil fuels. Subsidies will be given to transit companies to upgrade their vehicles. Additional funds from California's settlement with Volkswagen over "Diselgate" will be available as well. Electric and hydrogen fuel cell buses are expected to become cost-effective enough to replace the old fleet. Currently, only 153 out of the 12,000 buses in California are zero-emission vehicles.