Enhancements in Test Methods for Industrial-Grade Engines and Vehicles
The United States Environmental Protection Agency (EPA) has announced an update to the Greenhouse Gas Emissions Model (GEM) for heavy-duty vehicles. This Final Rule, identified as EPA-HQ-OAR-2019-0307, aims to improve the accuracy and representativeness of emissions testing for medium- and heavy-duty vehicles.
Purpose and Scope
The rule focuses on updating test procedures for heavy-duty engines and vehicles to enhance the measurement of greenhouse gas (GHG) emissions and fuel efficiency. The revisions will be reflected in the Greenhouse Gas Emissions Model (GEM), which is used by the EPA to evaluate GHG emissions from medium- and heavy-duty trucks and buses during regulation development and compliance assessment.
Impact on GEM
The improvements in testing methodologies will feed into GEM, making its simulations and regulatory standards more stringent and reflective of actual vehicle operation. This supports the EPA’s broader efforts to reduce emissions from the commercial vehicle sector.
Regulations for Heavy-Duty Trucks and Buses
The EPA has implemented progressively stricter standards targeting both nitrogen oxides (NOx) and greenhouse gases (e.g., CO₂). Starting in 2025, new heavy-duty vehicles must comply with updated NOx and CO₂ emission limits, following stricter engine and vehicle emission standards under EPA’s Clean Trucks Program.
The standards tighten further in 2027 and beyond, reflecting more stringent NOx and GHG limits designed to encourage adoption of advanced engine technologies and zero-emission vehicles (ZEVs), such as electric and hydrogen fuel cell trucks. This phased approach aligns with federal goals to reduce harmful pollutants and combat climate change by transitioning medium- and heavy-duty vehicles to cleaner technologies.
Coordination with State Programs
While EPA sets a national baseline, some states like California remain influential via stricter regulations under programs such as the Advanced Clean Trucks (ACT) and Advanced Clean Fleets (ACF), aiming for zero-emission fleets by 2035. However, recent federal actions in 2025 (via Congressional Review Act measures) have impacted California’s ability to enforce certain stricter emissions regulations, somewhat limiting state's regulatory scope.
No Significant Environmental or Economic Impact
The EPA has stated that this final action is not expected to have any significant environmental impacts or significant economic impacts.
The Final Rule for Improvements for Heavy-Duty Engine and Vehicle Test Procedures is available as a pdf document. For additional resources and information, please visit the EPA's website.
[1] EPA-420-R-22-014: Response to Comments on the Improvements for Heavy-Duty Engine and Vehicle Test Procedures [2] 40 CFR Part 1036 and 1037 [3] FMCSA/NHTSA proposal regarding speed limiters on heavy vehicles (July 2025) [4] GEM for the compliance process of medium- and heavy-duty vehicles
- The revised testing procedures for heavy-duty engines and vehicles, as outlined in EPA-HQ-OAR-2019-0307, will bolster the data in the Greenhouse Gas Emissions Model (GEM), aiding the assessment of emissions from medium- and heavy-duty trucks and buses in environmental-science studies.
- These updates in the GEM model will influence the development of stricter regulations in the industry, reflecting the growing focus on combating climate-change and encouraging the adoption of cleaner energy solutions such as electric and hydrogen fuel cell trucks.
- As federal and state efforts to reduce emissions continue, the intersection of technology and sports is likely to feature advanced data-and-cloud-computing solutions, ensuring accurate and timely emission tracking in sports-betting platforms, thus contributing to a greener sports ecosystem.
- In the realm of finance and business, investing in the automotive sector may prove crucial as companies transition to meet the stricter emissions standards set by the EPA and state programs like California's Advanced Clean Trucks (ACT) and Advanced Clean Fleets (ACF).
- Real-estate developers may also play a role in promoting sustainable practices, incorporating energy-efficient designs and technologies to minimize carbon footprints, aligning with the EPA's goal of reducing harmful pollutants and alleviating the impact of climate-change.
- The FMCSA/NHTSA's proposal regarding speed limiters on heavy vehicles, scheduled for July 2025, will add another layer of safety measures, with the potential to further optimize energy consumption and emissions in the transportation sector.
- While the EPA has announced that the Final Rule for Improvements for Heavy-Duty Engine and Vehicle Test Procedures will not have a significant environmental impact, ongoing advancements in technology and collaboration across industries will be essential in achieving long-term climate-change mitigation objectives.
