Heavy-duty Truck “Glider Kit” Rule

The Environmental & Energy Law Program is tracking the environmental regulatory rollbacks of the Trump administration. Click here for the list of rules we are following. If you’re a reporter and would like to speak with an expert on this rule please email us

Why It Matters

More than 25% of the nation’s greenhouse gas emissions come from the transportation sector (chiefly cars and trucks), which also accounts for more than 70% of oil used in the United States. Medium- and heavy-duty vehicles cause about a quarter of the total transportation-related greenhouse gas emissions. A “glider” or “glider kit” is essentially an old heavy-duty truck engine installed into a new chassis, largely to avoid modern pollution control requirements. Many of the engines used in gliders generate, for example, nitrogen oxides (NOx) and particulate matter (PM) emissions that are 20 to 40 times higher than new engines. In fact, EPA estimated when it proposed new rules addressing gliders, that gliders accounted for just 2% of sales of new heavy-duty trucks but up to one half of all NOx and PM emissions from new trucks.

EPA’s vehicle emissions standards change as engine technology improves. Before 2016, EPA regulated gliders on the basis of the engine manufacture year: they could be marketed as new but only subject to lower emissions standards for older engines rather than up-to-date pollution standards.

In 2016, EPA and the National Highway Transportation Safety Administration (NHTSA) issued joint comprehensive regulations limiting the greenhouse gas emissions and fuel consumption of medium- and heavy-duty trucks. The emissions regulations apply pollution control standards to gliders based on the year the entire truck was manufactured, not just the engine. Including gliders in the regulations largely eliminates the incentive to use these much dirtier engines in newly manufactured trucks. These regulations are projected to reduce greenhouse gas emissions by nearly 200 million metric tons by 2050, and to significantly reduce NOx and PM emissions as well.

Current Status

The EPA has issued a proposed repeal of the emissions requirements for gliders and the agency is considering a final repeal. The requirements for trailers from the 2016 rule are still subject to a stay, issued by the D.C. Circuit on October 27, 2017. The EPA’s July 6, 2018 announcement that it would not enforce the annual cap of 300 gliders per manufacturer until at least 2019 has been stayed by the D.C. Circuit, meaning the glider manufacturing cap will apply in 2018. Sixteen state attorneys general have also sued the EPA to challenge the announcement not to enforce the manufacturing cap. On July 26, 2018, Acting EPA Administrator Andrew Wheeler withdrew the Glider Announcement, meaning that EPA will enforce the annual manufacturing cap for gliders for 2018 and future years.



In 2011, EPA and NHTSA published Phase 1 regulations, Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles. All gliders were exempt from NHTSA’s Phase 1 fuel efficiency standards. Gliders manufactured by small businesses were exempted from EPA’s Phase 1 emissions requirements. The Phase 1 regulations went into effect on November 14, 2011.

On February 18, 2014, President Obama directed EPA and NHTSA to develop Phase 2 standards.

On July 13, 2015, EPA and NHTSA published a joint, proposed Phase 2 rule, Greenhouse Gas Emissions and Fuel Efficiency Standards: Medium- and Heavy-Duty Engines and Vehicles; Phase 2. Both agencies proposed including gliders as regulated entities and sought comments related to that proposal. Many of the large truck manufacturing companies supported, and still support, these regulations. In particular industry supports applying the applying the up-to-date pollution standards to gliders, as the sale of gliders undercuts the manufacturers’ investment in better emissions control technologies.

On October 1, 2015, the comment period for the proposed rule closed, after being extended on September 8, 2015.

On October 25, 2016, the agencies published the final rule with an effective date of December 27, 2016. EPA included regulations for reducing CO2 emissions from tractor trailers and gliders and set an annual manufacturing cap of 300 gliders per company. NHTSA affirmed its safety authority over gliders but did not finalize fuel efficiency standards for gliders. The implementation date for EPA’s new emissions standards for gliders was January 1, 2018.

On December 22, 2016, Truck Trailer Manufacturers Association, Inc. (TTMA) filed a petition for review in the D.C. Circuit Court of Appeals challenging EPA and NHTSA rules, Truck Trailer Manufacturers v. EPA, et al., Docket No. 16-01430. TTMA argued that the agencies exceeded their statutory authority in promulgating the new rule which regulates tractor trailer emissions by setting aerodynamic equipment requirements. Specifically, TTMA asserted that trailers could not be considered new vehicles under the Clean Air Act, and thus EPA did not have the authority to regulate them.

On December 26, 2016, Racing Enthusiasts and Suppliers coalition also filed a petition for review, Racing Enthusiasts and Sup. v. EPA, et. al., Docket No. 16-1447. This case was consolidated with TTMA’s case.

Trump Era

On January 23, 2017, seven states, the California Air Resources Board, and environmental groups joined the lawsuit on behalf of EPA and NHTSA.

On April 3, 2017, TTMA sent letters to NHTSA and EPA requesting that the agencies review, reconsider, and rescind the trailer standards.

On April 20, 2017, EPA and NHTSA filed a motion to delay the case in light of TTMA’s request to reconsider. TTMA partially opposed this motion because EPA had yet to finalize a decision to reconsider the rule.

On May 8, 2017, the court put the case on hold for 90 days, twice extending that period as EPA continued to review TTMA’s request to reconsider the rule.

On August 17, 2017, EPA and NHTSA responded to TTMA’s request and agreed to reconsider the rule.

On September 25, 2017, TTMA submitted a motion for a stay of the requirements for trailers, which would stop those standards from going into effect.

On October 12, 2017, EPA declared that it would take no position on TTMA’s motion for a stay. The state intervenors and environmental groups opposed the motion.

On October 27, 2017, the court ordered that the case continue to be put on hold and that the requirements for trailers be suspended.

On November 16, 2017, EPA issued a proposed repeal of the emissions requirements for gliders. Comments to the proposed repeal were due on January 5, 2018.

EPA filed a status report with the court on January 22, 2018, stating that the agency is developing a rule to revisit the trailer provisions of the rule.

On February 8, 2018, the California Air Resources Board adopted the 2016 Final Rule standards for glider kits produced in California.

On February 19, 2018, the president of Tennessee Tech University sent a letter to EPA Administrator Scott Pruitt requesting that the agency not use or reference a Tennessee Tech study, which found that glider engines and new engines produced similar amounts of emissions. The University is investigating the validity of the study, which was funded by one of the nation’s largest glider kit manufacturers, after experts questioned its methodology. Industry relied on the study in its request to EPA to reconsider the rule, and EPA referenced industry’s reliance on the study in the proposed repeal.

In March 2018, fourteen Republican members of Congress (four senators and ten representatives) sent letters to EPA Administrator Scott Pruitt asking the agency not to repeal the emissions standards for glider vehicles because it will undermine manufacturing industries in their home states.

On July 6, 2018, the EPA announced that it would not enforce the annual cap of 300 gliders per manufacturer, at least through the end of 2019. EPA is considering formally delaying the glider manufacturing cap until December 2019 and working to repeal it in the meantime.

On July 13, 2018, a coalition of thirteen Attorneys General submitted a letter to the EPA, urging the Acting Administrator, Andrew Wheeler, to withdraw the Glider Announcement that suspends the manufacturing cap or change course and enforce the cap.

On July 17, 2018, a coalition of environmental advocacy groups filed an emergency motion in the U.S. Court of Appeals for the D.C. Circuit, asking the court to enforce the manufacturing cap or halt the EPA’s Glider Announcement. Both requests have the same outcome- the cap will go into effect for 2018, either by court enforcement or by the court halting the Glider Announcement.

On July 18, 2018, the D.C. Circuit granted the emergency motion and issued an administrative stay, halting the EPA’s Glider Announcement of not enforcing the glider manufacturing cap. So, the cap will go into effect for 2018 while the court considers the issues raised in the motion. 

On July 19, 2018, a coalition of sixteen state attorneys general filed a lawsuit challenging the EPA’s Glider Announcement. The coalition includes the attorneys general of California, Delaware, Illinois, Maine, Maryland, Massachusetts, New Jersey, New York, New Mexico, North Carolina, Oregon, Pennsylvania, Rhode Island, Vermont, Washington, and the District of Columbia, as well as the California Air Resources Board, the Minnesota Pollution Control Agency, and the Pennsylvania Department of Environmental Protection.

On July 26, 2018, Acting EPA Administrator Andrew Wheeler withdrew the Glider Announcement, meaning that EPA will enforce the annual manufacturing cap for gliders for 2018 and future years.

On August 21, 2018, the Assistant Administrator for Air and Radiation at EPA, Bill Wehrum, sent a letter to the Chairman of the House Science, Space and Technology Committee defending the agency’s emissions testing and findings on glider kit trucks.

On September 13, 2018, the House Subcommittee on Oversight and Subcommittee on Environment held a hearing, “Examining the Underlying Science and Impacts of Glider Truck Regulations.”

On October 23, 2018, Tennessee Tech released a letter stating that the university’s internal investigation of the controversial glider truck study found that the study’s field-testing procedures “were not sufficient to justify comparison with EPA emissions standards” and “the data does not support” the finding that glider trucks performed as well as certified engines. 

For More Information

For more on this rule see  Save EPA’s post on this rule and their comments to EPA on the rollbacks. 

Thank you to Harvard student Laura Bloomer, JD/MPP 2019 and William Neibling, Research Counsel and JD 2013, for their assistance with this rule.

HLS Student Orgs

Search Our Site

HLS Evironmental Law on Twitter