Engine manufacturers using selective catalytic reduction (SCR) emission control technology have new federal guidance allowing them to more gradually “derate” systems when diesel exhaust fluid (DEF) depletes.

U.S. Environmental Protection Agency (EPA) Administrator Lee Zeldin announced during the Iowa State Fair last week the new action designed to protect American farmers, truckers and other diesel equipment operators from sudden speed and power losses caused by DEF systems.

“We have heard loud and clear from small businesses across the U.S. that the current DEF system is unacceptable,” Zeldin said in a statement. “It is unacceptable that farmers, truckers, construction workers, and many other small businesses continually experience failures of diesel-powered equipment when they need it most—costing millions of dollars in lost productivity. Today, we are responding to those concerns by calling on manufacturers to take action to update their software and eliminate the unnecessary sudden loss of power and frustrating shutdowns that too many Americans have experienced.”

EPA issued the guidance urging diesel engine and off-road farm equipment manufacturers to revise DEF system software in existing vehicles and equipment to prevent these sudden shutdowns. Starting with model year 2027, all new diesel on-road trucks and motorcoaches must be engineered to avoid sudden and severe power loss after running out of DEF.

EPA said it also has a fix for derate issues in legacy diesel vehicles with SCR.

“To fix the problem for vehicles already in use, EPA’s new guidance, developed in collaboration with manufacturers, will work to ensure that the necessary software changes can be made on the existing fleet,” the press release notes. “In addition to providing certainty to manufacturers about how EPA wants this issue resolved, the agency is not requiring separate approvals beyond that provided in EPA’s guidance. This ensures that bureaucratic steps do not delay manufacturers’ ability to put solutions into the field.”

Since 2010, SCR has used on-board diagnostics sensors to detect when DEF runs out or diesel particulate filters clog and then initiate a rapid derate of the engine. Within four hours of DEF depletion, vehicles automatically slow to five miles per hour.

But the results for industries have been “catastrophic,” said EPA, as disruptions have occurred to logistics, agriculture and construction. Several diesel engine manufacturers also initiated recalls over their SCR technology. Cummins recalled 2010 to 2015 medium- and heavy-duty engines, including the ISB 6.7 for school buses, because the SCR unit catalysts degraded faster than expected.

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“At Cummins, we recognize our responsibility in powering some of the country’s most economically vital applications, from the buses that take our kids to and from school to the trucks that deliver critical goods,” a statement from the company reads. “Collaboration with our customers is at the heart of what we do, ensuring we deliver solutions that meet their business needs while continuously innovating to improve fuel efficiency, reduce costs and enhance reliability. SCR is a widely accepted, proven technology utilized in many applications, and we are committed to working closely with the EPA and the select customers affected by SCR inducements. Together, we aim to provide regulatory certainty, greater flexibility and the dependable solutions that contribute to the American economy.”

Daimler Truck North America told School Transportation News it welcomes the new guidance.

“We are supportive of the efforts to provide more flexibility with regard to DEF inducement and are actively working on solutions to support our customers,” the statement reads.

The Engine Technology Forum and several other organizations also support the new derate guidance.

“EPA has heard from users of diesel trucks, tractors and equipment and, working with manufacturers, has responded with these adjustments to improve operational performance while ensuring emissions integrity,” Executive Director Allen Schaeffer said. “EPA’s announcement [Aug. 12] provides new guidance that allows manufacturers to adjust these systems to ensure that farmers, motor coach operators, and truckers, who all rely on diesel engines and equipment, will be able to complete critical work with sufficient lead time for scheduling maintenance and repairs.”

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The Environmental Protection Agency on Tuesday announced sweeping changes to rules governing diesel exhaust fluid (DEF) systems, aimed at preventing sudden power losses that have long frustrated farmers, truckers and bus operators.

The Trump administration says the guidance, which takes effect immediately, will ease operational disruptions and reduce safety risks while maintaining emissions standards.

EPA Administrator Lee Zeldin unveiled the changes during a press call from the Iowa State Fair alongside Small Business Administrator Kelly Loeffler, Agriculture Secretary Brooke Rollins and Sen. Joni Ernst, R-Iowa.

“The United Motorcoach Association applauds the new guidance from the Environmental Protection Agency (EPA) under the leadership of Administrator Lee Zeldin regarding Diesel Exhaust Fluid regulations for motorcoaches,” remarked UMA’s President and CEO Scott Michael. “EPA’s new guidance will improve safety, avoid passengers stranded on the side of the road, and unnecessary towing costs while maintaining the goal of safeguarding the environment.”

The policy allows manufacturers to reprogram existing vehicles to avoid abrupt “derates” — a rapid reduction in engine power — that can cut a vehicle’s speed to as little as 5 mph within hours of a DEF system fault.

“This is yet another common-sense policy,” Zeldin said. “We can protect the environment and grow the economy at the same time.”

Under current rules, a sensor failure in a DEF system can trigger severe speed limits within four hours, sometimes leaving vehicles stranded mid-operation. Zeldin said the new guidance will extend that timeline significantly.

‘Massive Deregulation’

Loeffler said the new policy will save America’s 1.8 million family farms an estimated $727 million annually.

“This is massive deregulation,” she said. “It’s solving a huge, long-standing issue that has gone on for 15 years.”

Rollins called the announcement “a big deal” for producers already struggling with higher costs and frequent downtime.

“We’re doing God’s work,” she said. “This is how we return power to the people and get the strangulation of overregulation out of everyday mom-and-pop small business owners’ lives, especially our farmers.”

While much of the call centered on agriculture and freight, Zeldin emphasized the rule’s importance for the passenger transportation industry.

“This was one of the concerns we heard from bus operators,” Zeldin told Bus & Motorcoach News. “It’s a safety concern when a bus is forced to park unexpectedly on the side of the road for an extended period of time. That’s all a product of poor government policy that didn’t think through the consequences.”

Phil Streif, of Vandalia Bus Lines in Caseyville, Illinois, told Bus & Motorcoach News in a separate interview that the change is the result of years of advocacy to bring operators’ perspectives to federal regulators. Streif began contacting the EPA five years ago, warning that the four-hour repair window was “just not realistic” for the motorcoach industry.

“After countless meetings with EPA and CARB, we finally got relief,” Streif said, “but the question remained about existing fleets.”

That question led to additional negotiations — and resistance from some engine manufacturers — before regulators agreed to modify the rules for vehicles already in service.

Uncertainty over future federal regulations already has disrupted one engine maker’s plans. Cummins Inc., a manufacturer of diesel engines, announced this month the postponement of the launch of its new X15 diesel engine for heavy-duty trucks to late 2026.

Initially unveiled in February with features meeting 2027 EPA and CARB standards, the engine was set for pre-orders in mid-2025 and deliveries in 2026. A statement from Cummins touted the technology used in the X15.

“Selective Catalytic Reduction (SCR) is a widely accepted, proven technology utilized in many applications, and we are committed to working closely with the EPA and the select customers affected by SCR inducements. Together, we aim to provide regulatory certainty, greater flexibility, and the dependable solutions that contribute to the American economy.”

Ending a Safety Risk

Streif said two moments proved decisive in resolving the derating issue: meeting EPA’s Amy Kopin, “who strongly advocated for us,” and the change in agency leadership when Zeldin took over. “They came out early, promising a goal to reduce regulation and the red tape that makes our businesses more challenging to operate. After many exchanges, we made great progress, and now we’re finally at the finish line.”

The new rules give bus operators 40 hours before even a minor torque reduction — something Streif calls “a game changer.”

“There are so many things that run through your head when you see an inducement code and know you have four hours before the bus is essentially inoperable,” he said. “We’re moving the most precious cargo there is — people — and derating created a profound safety risk for our drivers and passengers.”

Streif recounted an incident just two weeks ago in which a bus in New Orleans began showing a DEF-related fault code. Mechanics attempted repairs, but the problem reappeared within hours, forcing the company to dispatch a replacement bus from Alabama to ensure passengers could return home on time.

“Something that could have waited until we got the bus back created an obstacle for us that we had limited options for,” he said.

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The industry’s challenge was compounded by the scarcity of repair shops for motorcoaches, especially in remote areas or during off-hours. “There were no signs that could predict when a sensor would go bad, so it was like rolling the dice every time a bus went out,” Streif said.

Streif credited the American Bus Association, United Motorcoach Association, and International Motorcoach Group with helping build the case for reform.

“With their help and many members’ feedback, we were able to collect hard data and surveys that provided factual statistics on the impact derates have,” he said. “Honestly, without the strength of these great organizations, we probably wouldn’t have the results we were able to achieve.”

Putting Focus on Bus Industry

The advocacy also exposed a gap in federal oversight. “When I initially reached out to the EPA, their response was, ‘Oh, we didn’t even consider buses,’” Streif said. “It’s been stated before that our industry has been left out in the past, but I think that’s going to change going forward.”

He said the industry will need to maintain its presence in regulatory discussions. “Although our industry is small, we all work together in a way that other industries don’t see. That’s what will make us successful as long as we continue to support one another.”

Ernst praised the EPA’s move, calling the previous guidelines “arbitrary” and harmful to productivity. She also tied the changes to broader Republican efforts to roll back regulations enacted during the Biden administration.

Zeldin said the change reflects a broader philosophy of governance.

“Today’s guidance bridges the gap between now and 2027, ensuring existing vehicles on the road and in the field are just as dependable,” he said. “We’re both protecting human health and the environment and the people who depend on diesel engines to do their job.”

The EPA said no additional agency approval will be required for manufacturers to implement the new software changes.

For Streif, the new timeline — 40 hours before a small torque derate, then 200 hours before a 50 mph limit — is one the industry can live with. “On flat stretches we won’t see any impact,” he said. “I think we can all live with that.”

This article is reprinted with the permission of Bus and Motorcoach News. Read the original post here.

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COLUMBUS, Ind. — Cummins Inc. (NYSE: CMI) today reported results for the second quarter of 2025.

“We delivered strong second quarter results, driven by record profitability in our Power Systems and Distribution segments,” said Jennifer Rumsey, Chair and CEO. “Our employees’ resilience and commitment continue to power our success in a dynamic environment. We see a contrast across our markets with robust demand for power generation equipment supported by clear secular drivers, and our more economically sensitive markets, such as truck, where end-user confidence has declined. This contrast will become even more pronounced in the second half of the year as North America truck build rates decline sharply, starting in the third quarter. Aftermarket demand for parts and service remains stable.”

Second quarter revenues of $8.6 billion decreased 2 percent from the same quarter in 2024. Sales in North America declined 6 percent, and international revenues increased 5 pecent due to higher demand in Europe and China.

Net income attributable to Cummins in the second quarter was $890 million, or $6.43 per diluted share, compared to $726 million, or $5.26 per diluted share, in 2024.

Earnings before interest, taxes, depreciation and amortization (EBITDA) in the second quarter were $1.6 billion, or 18.4 percent of sales, compared to $1.3 billion, or 15.3 percent of sales, a year ago.

2025 Outlook

Due to continued economic uncertainty, the company will not be reinstating a full-year outlook for revenue or profitability at this time.

“Our diversified portfolio, disciplined cost management and strong execution have enabled us to navigate recent industry challenges,” said Rumsey. “However, persistent economic and regulatory uncertainty continues to impact a number of our key markets and cloud our near-term outlook for both business and market performance. We remain focused on delivering for our customers and look forward to providing additional clarity as this uncertainty subsides.”

Second Quarter 2025 Highlights

Cummins announced an increase in the quarterly common stock cash dividend from $1.82 to $2.00 per share. The company has increased the quarterly dividend to shareholders for 16 consecutive years.

Cummins launched the new 17-liter engine platform generator, expanding on the success of the acclaimed Centum Series generator sets. Producing up to 1 megawatt of power, the S17 Centum genset was developed to produce a large power output within a compact footprint to meet the growing demands of power in urban environments. The new genset is designed to support a wide range of critical market segments such as commercial properties, healthcare facilities and water treatment plants.

Jennifer Rumsey was named one of Barron’s Top CEOs of 2025. Jennifer was recognized for her visionary leadership and commitment to innovation and sustainability. The annual list features 26 leaders whose deft guidance has put their companies in a stronger competitive position.

Second Quarter 2025 Detail (all comparisons to same period in 2024):

Engine Segment

• Sales – $2.9 billion, down 8 percent
• Segment EBITDA – $400 million, or 13.8 percent of sales, compared to $445 million, or 14.1 percent of sales

Revenues decreased 8 percent in North America and 7 percent in international markets due to lower on-highway demand in the United States and Mexico.

Components Segment

• Sales – $2.7 billion, down 9 percent
• Segment EBITDA – $397 million, or 14.7 percent of sales, compared to $406 million, or 13.6 percent of sales

Revenues in North America decreased by 15% and international sales were flat primarily due to lower on-highway demand in the United States.
Distribution Segment

• Sales – $3.0 billion, up 7 percent
• Segment EBITDA – $445 million, or 14.6 percent of sales, compared to $314 million, or 11.1 percent of sales

Revenues in North America increased 9 percent and international sales increased by 4% primarily due to increased demand for power generation products in the United States.
Power Systems Segment

• Sales – $1.9 billion, up 19%
• Segment EBITDA – $430 million, or 22.8% of sales, compared to $301 million, or 18.9% of sales

Revenues in North America increased 23% and international sales increased 16% driven primarily by increased power generation demand, particularly for the data center and mission critical markets.

Accelera Segment

• Sales – $105 million, down 5 percent
• Segment EBITDA loss – $100 million, compared to $117 million

Revenues decreased due to lower electrolyzer installations. The company remains committed to pacing and focusing our zero emissions investments on the most promising paths in order to ensure we are set up for long-term success as part of our Destination Zero strategy. These continued investments contributed to the EBITDA losses.
About Cummins Inc.

Cummins Inc., a global power solutions leader, is comprised of five business segments – Engine, Components, Distribution, Power Systems and Accelera by Cummins – supported by our global manufacturing and extensive service and support network, skilled workforce and vast technological expertise. Cummins is committed to its Destination Zero strategy, which is grounded in the company’s commitment to sustainability and helping its customers successfully navigate the energy transition with its broad portfolio of products. The products range from advanced diesel, natural gas, electric and hybrid powertrains and powertrain-related components including aftertreatment, turbochargers, fuel systems, valvetrain technologies, controls systems, air handling systems, automated transmissions, axles, drivelines, brakes, suspension systems, electric power generation systems, electrified power systems with innovative components and subsystems, including battery, fuel cell and electric power technologies and hydrogen production technologies. Headquartered in Columbus, Indiana (U.S.), since its founding in 1919, Cummins employs approximately 69,600 people committed to powering a more prosperous world through three global corporate responsibility priorities critical to healthy communities: education, environment and equality of opportunity. Cummins serves its customers online, through a network of company-owned and independent distributor locations, and through thousands of dealer locations worldwide and earned about $3.9 billion on sales of $34.1 billion in 2024. See how Cummins is powering a world that’s always on by accessing news releases and more information at https://www.cummins.com.

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The U.S. Environmental Protection Agency is reconsidering the 16-year-old Obama administration ruling on greenhouse gases that formed the nation’s regulatory landscape for transportation emissions, including those for school buses.

The proposed rule rolled out by EPA Administrator Lee Zeldin Tuesday at an auto dealership in Indianapolis, Indiana could save more than $54 billion annually in manufacturing costs passed on to consumers, EPA said. It claims emissions regulations implemented over the past 15 years created $1 trillion in costs to manufacturing, power and industrial sectors for meeting various emissions requirements.

While the 300-page document does not mention school buses by name, it focuses on repealing GHG emission standards for various categories of vehicles, including the categories of medium- and heavy-duty trucks and engines that school buses fall under.  Specifically, it seeks to remove Part 85 on control of air pollution from mobile sources, Part 86—Control of Emissions from New and In-use Highway Vehicles and Engines, Part 600—Fuel Economy and Greenhouse Gas Exhaust Emissions of Motor Vehicles, Part 1036—Control of Emissions from New and In-use Heavy Duty Highway Engines, Part 1037—Control of Emissions from New Heavy Duty Motor Vehicles, and Part 1039—Control of Emissions from New and In-use Non-road Compression-Ignition Engines.

Already, EPA is reconsidering the implementation of its GHG Phase 3 Rule for heavy-duty trucks and buses that is set to start in 2027.

The proposed rule seeks to reinterpret the Clean Air Act, specifically Section 202(a), known as the Endangerment Finding, which concluded that carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride contribute to air pollution and endanger public health. The proposed rule argues that the Endangerment Finding is legally flawed, scientifically uncertain and economically counterproductive. EPA claims it was historically applied to address local and regional air pollution, not global climate change concerns.

This interpretation exceeded statutory authority, writes EPA, adding that Congress did not clearly authorize the EPA to regulate GHG emissions based on global climate change concerns “because that provision authorizes regulating only air pollutants that ‘cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare.’”

The proposed rule also notes the U.S. Supreme Court rulings in West Virginia v. EPA and Utility Air Regulatory Group v. EPA that federal agencies cannot assert transformative regulatory authority without explicit congressional approval. Instead, agencies must have more than a “colorable textual basis” to decide major questions of policy.

EPA also questions “unreasonably analyzed” scientific data used to support the original “Endangerment Finding” that declared GHG to endanger public health and welfare. The proposed rule cites projections of global warming increases, health risks from heat waves, and impacts of other health events. It also notes empirical data, peer-reviewed studies and real-world developments since 2009 that “cast significant doubt on many of the critical premises, assumptions and conclusions in the Endangerment Finding.”

The proposal also claims technological limitations in addressing global climate change concerns, as “reducing GHG emissions from all vehicles and engines in the U.S. to zero would not have a scientifically measurable impact on GHG emission concentrations or global warming potential,” according to a May 27 draft report by the U.S. Department of Energy Climate Working Group.

EPA also notes President Donald Trump’s recent “One Big Beautiful Bill Act” repealed certain GHG provisions.

As for economic concerns, EPA highlighted that GHG emissions standards have increased vehicle costs, slowed fleet turnover and reduced consumer access to newer, safer and more efficient vehicles.

Public comments on EPA-HQ-OAR-2025-0194 are due by Sept. 21.

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David Weber, business development manager for School-Radio, analyzes new bus radio and communication technology solutions that can optimize district operations.

Regional Sales Manager James Holtz gives us a glimpse of the innovative new electric school bus Blade Battery from RIDE.

Amidst rapid developments in the clean fuel school bus market, Francisco “Paco” Lagunas, general manager of the North American bus market for Cummins, and Richard Garvin, director of strategy and commercial business development, present answers from the energy leader.

Director of Transportation Teri Mapengo discusses operations, technology and fostering the kind of positive workplace culture that won Prosper Independent School District in Texas a Top Transportation Teams award at this week’s STN EXPO in Reno, Nevada.

Read more STN EXPO West coverage.

This episode is brought to you by Transfinder.

Conversation with RIDE.

Conversation with School-Radio.

Conversation with Cummins

Stream, subscribe and download the School Transportation Nation podcast on Apple Podcasts, Deezer, Google Podcasts, iHeartRadio, RadioPublic, Spotify, Stitcher and YouTube.

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