S-1779-119
Read twice and referred to the Committee on Environment and Public Works.
Sponsored by Joni Ernst (R-IA)
What it does
This bill would amend Section 209(e)(1) of the Clean Air Act to extend the existing federal preemption of state emissions standards to cover all existing locomotives and locomotive engines engaged in interstate commerce — not just new ones. Currently, states are prohibited from setting their own emissions rules for new locomotives, but the bill would close what sponsors see as a gap by explicitly preempting state rules for older, in-service locomotives as well. The bill would apply to all locomotives providing common carrier railroad transportation for compensation under federal law.
Who benefits
Freight railroad companies operating older locomotive fleets across multiple states, who would face a single federal standard rather than a patchwork of state rules. Shippers and supply chains that depend on rail freight, who could see reduced compliance-related cost increases passed through by railroads. States without their own locomotive emissions rules, which would not be disadvantaged relative to states with stricter standards. Consumers who may benefit if reduced railroad compliance costs lower the cost of transported goods.
Who is hurt
States — particularly California, which has adopted its own locomotive emissions rules through the California Air Resources Board (CARB) — that would lose authority to set stricter standards for existing locomotives operating within their borders. Residents of those states who live near rail yards and freight corridors and who may be exposed to higher levels of diesel particulate matter and nitrogen oxides than they would be under state rules. Environmental and public health advocacy organizations that have supported state-level locomotive emissions standards. Workers and communities near rail yards in states with stricter rules who may experience reduced air quality improvements.
Supporters argue
Supporters argue that railroads are an inherently interstate mode of commerce and that a locomotive operating across dozens of states cannot practically comply with a different emissions standard in each jurisdiction. They contend that California's CARB locomotive rules — which would require railroads to retrofit or retire large portions of their existing fleets — impose billions of dollars in compliance costs that threaten the economic viability of freight rail, potentially shifting cargo to trucks, which produce significantly more emissions per ton-mile. They argue that uniform federal standards, set by the EPA, are the appropriate mechanism for regulating an industry that crosses state lines by definition.
Opponents argue
Opponents argue that the Clean Air Act has long allowed California and other states to set stricter air quality standards precisely because federal minimums are insufficient to protect public health in high-pollution areas. They contend that communities near rail yards — which are disproportionately low-income and communities of color — bear the greatest health burden from locomotive diesel emissions, and that stripping state authority removes the most effective tool those communities have. They argue that the bill would freeze in place a fleet of older, high-polluting locomotives indefinitely, undermining decades of state-level air quality progress without guaranteeing that the EPA will adopt equivalent federal standards.
Constitutional context
The Commerce Clause (Art. I, §8, cl. 3) gives Congress broad authority to regulate interstate commerce, including railroads, and to preempt state law in that domain. The Clean Air Act's existing preemption framework for mobile sources has been upheld under this authority. However, post-Loper Bright (2024), any EPA rulemaking that fills the gap left by preempted state standards would face independent judicial scrutiny rather than deference, raising questions about whether existing federal locomotive emissions rules provide adequate regulatory coverage.
Checks and balances
Congress would gain authority by explicitly preempting state law; states lose regulatory power over existing locomotive emissions; the EPA retains exclusive federal rulemaking authority, subject to independent judicial review under Loper Bright.
Historical precedent
The Clean Air Act already preempts state emissions standards for new locomotives under Section 209(e)(1)(B); this bill extends that preemption to existing locomotives, analogous to the longstanding federal preemption of state standards for new on-road motor vehicles under Section 209(a).