This blog is co-authored by NRDC’s Britt Carmon, Guillermo A. Ortiz, and David Pettit. It originally appeared here.
California has long grappled with the challenge of improving its air quality, which ranks as the worst in the country. Heavy-duty diesel trucks, which are significant contributors to air and climate pollution, make it difficult for the state to achieve nationwide air quality standards. As such, it should be no surprise that the transportation sector remains the largest source of greenhouse gas emissions, not only in California, but nationwide as well. However, the scale of the problem is not insurmountable. California has also been at the forefront of regulating tailpipe and motor vehicle greenhouse gas emissions and has made steady progress towards cleaner air for decades.