State's war on carbon emissions faces setbacks in court and Congress | Beyond legislative and legal headwinds, sales of zero-emission vehicles are falling short of California’s interim goals

It's worth nothing that vehicle tailpipes are the biggest source of greenhouse gas emissions in California. and the one other lever available is to try to reduce driving. That means no more freeway expansions, and putting that money into mass transit and bike access so that people don't need cars as much.