Unsurprisingly, the freight business is a bit nervous. The California Trucking Association is worried that the more efficient tech might prove "costly," and wants to work with the state on any solutions. However, companies might not have much of a choice. While pollution levels are getting better overall, they're still particularly bad in places like Los Angeles -- it's doubtful that California will let smoke-spewing commercial vehicles carry on while everyone else moves on to greener options.

[Image credit: AP Photo/Jae C. Hong]