"In the absence of federal action to address harmful emissions from locomotives, CARB is developing regulatory concepts to reduce criteria pollutants, toxic air contaminants, and greenhouse gas emissions for locomotives in-use," CARB says on its website. "These concepts are intended to be implemented statewide, and provide an opportunity for the railroads to better address regional pollution and long-standing environmental justice concerns with communities near railyards. The goal of the regulatory concepts is to accelerate immediate adoption of advanced cleaner technologies for all locomotive operations."

The proposed regulation, which would apply to both passenger and freight rail operations that involve travel to seaports, rail yards and other locations, consists of the following:

In 2024:

Locomotive operators would need to fund a trust account based on how much emissions their locomotives produce and that account would help fund the purchase of cleaner locomotives or the upgrade of existing locomotives.

Locomotives with automatic shutoff devices would not be permitted to idle for longer than 30 minutes, except for certain circumstances such as maintaining air brake pressure or providing heat or cooling to the locomotive cab.

Locomotives operating in the state would be required to register with CARB and locomotive activity, emission levels and idling data would be reported annually.