California leads the way with first-ever train emission regulations.

California has become the first state to adopt emission rules for trains, with a new rule that will ban locomotive engines more than 23 years old by 2030 and increase the use of zero-emissions technology to transport freight from ports and throughout railyards. The standards would also reduce chemicals that contribute to smog. However, some say it's too soon for the locomotive standards, and the rail industry says the technology isn't there yet. The proposed rules would need federal backing to move forward.