Who is affected and how:

• Railroad carriers and freight/passenger rail operators: They become more directly subject to the Clean Air Act provision as amended if their locomotives are not already covered, potentially facing new regulatory obligations, retrofit requirements, emissions testing, or permitting depending on subsequent agency action. Compliance costs could arise for retrofits, replacements, monitoring, or administrative processes.

• Locomotive manufacturers and remanufacturers: They may face changes in design, certification, or production requirements if agencies develop new standards or certification regimes relying on the expanded statutory coverage.

• Communities near rail lines (including environmental justice communities): These communities could benefit from the statutory basis for tighter regulation of locomotive emissions, with potential air quality and public health improvements over time if standards are adopted and enforced.

• Environmental regulators (EPA and state agencies): The amendment expands the statutory authority and scope regulators can rely on when targeting locomotive emissions; regulators will need to interpret the change and may start rulemaking or guidance efforts.

• Indirectly affected parties: shippers, rail suppliers, and transit agencies could see cost or operational impacts passed through if locomotives require modification or replacement.

Overall impact: The change is narrowly focused — it adjusts statutory coverage to include locomotives under a specific Clean Air Act listing. The practical effects depend heavily on subsequent agency interpretation and rulemaking. It creates the legal basis for regulation of locomotives under that provision and therefore can lead to compliance costs for industry and air quality benefits for affected communities, but it does not itself specify standards, timelines, or funding.