Abstract:California has been a leader in advancing policy solutions to environmental and energy challenges since the 1960s. Many of those policy innovations have spread worldwide. Beginning with statutes passed by the California legislature starting in 2002 and continuing through today, California is adopting a comprehensive set of policies, regulations, and incentives to reduce greenhouse gas emissions, with particular emphasis on those associated with transportation—vehicles, fuels, and mobility. This paper reviews California's policy and regulatory approach related to transportation and highlights energy and climate policy lessons. The portfolio policy approach requires wise oversight, which will become more critical as California begins to adopt policies and rules to achieve more aggressive targets for 2030 and beyond. The shortcomings of a California-only policy approach will be overcome by expanding policy collaboration with other jurisdictions.