California leads the way with strict diesel-engine and train emissions rules.

California has passed new rules to limit emissions from diesel-fueled locomotive engines, requiring the phase-out of inefficient locomotive engines more than 23 years old by 2030, increasing the use of zero-emissions technology to transport freight from ports and throughout rail yards, and banning diesel-spewing engines from idling for longer than 30 minutes. Diesel emissions are responsible for some 70% of Californians’ cancer risk from toxic air pollution. The rule would also drastically cut greenhouse gas emissions from locomotives by an amount akin to removing all heavy-duty trucks from the state by 2030.