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EPA to develop options to reduce NOx and PM from locomotives further

The US Environmental Protection Agency (EPA) is responding to petitions from the California Air Resources Board, the San Joaquin Valley Air Pollution Control District, and the California Air Pollution Control Officers Association to address harmful nitrogen oxide (NOx) and particulate matter (PM) emissions from locomotives.

EPA adopted its first regulation to control the emissions from new locomotives and their engines in 1998. In that 1998 rule, EPA adopted three tiers of emission standards: Tier 0, Tier 1, and Tier 2. The Tier 2 standards began phasing in for new locomotives and engines built in 2005. This rulemaking action included requirements at the time of remanufacturing, as well as in-use testing requirements.

In 2008, EPA promulgated regulations addressing air pollutant emissions from locomotives. That three-part program aimed to:

  1. tighten emissions standards for existing locomotives when they are remanufactured, which under EPA’s rule makes them new again;

  2. set near-term engine-out emissions standards, referred to as Tier 3 standards, for newly-built locomotives and engines; and

  3. set longer-term standards, referred to as Tier 4 standards, for newly-built locomotives and engines that reflect the application of high-efficiency aftertreatment technology.

EPA estimates that use of a Tier 4 locomotive or engine represents a 90% PM emissions reduction and an 80% NOx emissions reduction, compared to a locomotive engine meeting the Tier 2 standards.

However, while that rule put in place lower emission standards for new locomotives and new locomotive engines, in California and elsewhere locomotives remain a significant source of NOx and PM emissions, often disproportionately impacting the health of communities near railyards and ports. In addition, the very slow natural fleet turnover of this sector results in older locomotives and locomotive engines remaining in use for decades.

The petitioners requested that the Environmental Protection Agency (EPA) undertake rulemaking to adopt more stringent national emission standards under the Clean Air Act (CAA) regulating nitrogen oxide (NOx) and particulate matter (PM) emissions from locomotives.

As part of EPA’s response to these petitions, EPA said is taking immediate steps to develop options and recommendations to address pollution from new locomotives as well as those already operating in communities nationwide.

Additionally, EPA plans to propose revisions to existing locomotive preemption regulations to ensure they don’t inappropriately limit California’s and other states’ authorities under the Clean Air Act to address their air quality issues.

Further, EPA has formed a rail study team to evaluate how best to address air pollutant emissions from the locomotive sector. In the coming months, this team will collect information and evaluate the following:

  • a range of technologies that may be available to further reduce locomotive emissions;

  • policy options to accelerate locomotive fleet turnover to newer, cleaner technology;

  • policy options to ensure that remanufactured locomotives are as clean as possible; and

  • engagement with partners, such as state, non-governmental organizations, environmental justice organizations, and industry stakeholders, to gather input as needed to inform the required evaluations.

Additionally, the passing of the “Inflation Reduction Act” (IRA) provides an enormous opportunity in the locomotive space. This funding accelerates the transition to a zero emissions future by providing funding opportunities in so many subsectors of transportation. EPA will explore opportunities to leverage these historic resources moving forward.


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