Diesel School Buses Continue Market Domination Amid Move Toward Lower-Emission Alternatives
New data shows that nearly three-quarters of all registered school buses are powered by diesel, even as the U.S. Environmental Protection Agency Clean School Bus Program is expected to extend federal funding to include the fuel.
The S&P Global Mobility TIPNet data for December 2025 indicates internal combustion engines account for 98 percent of all power in U.S. commercial vehicles, 76 percent being fueled by diesel. Gasoline is powering 23 percent followed by 0.5 percent natural gas and propane. Electric vehicles account for the other 0.5 percent.
A deeper analysis conducted this spring by the Engine Technology Forum (ETF) found that school districts are opting to replace their aging school bus fleets with diesel. The ETF said 72 percent of the 2010 and newer model-year school buses are diesel, a 5-percent increase from 2023. The diesel buses rely on SCR and particulate matter filters, the latter introduced in 2007, to reduce levels of PM and nitrogen oxide, or NOx, by more than 90 percent compared to pre-2007 engines.
“Fleet turnover is one of the most effective tools we have to improve air quality today,” said Allen Schaeffer, executive director of ETF, in a statement last week. “The increasing share of 2010 [and older] model-year diesel buses show that school districts are making practical, cost-effective investments that deliver immediate environmental and operational benefits for students.”
Meanwhile, diesel school buses make up over 87 percent of the total fleet of school buses. The ETF analysis found about 18 percent of the national fleet regardless of fuel are pre-2007 model years.
The analysis also found that electric school buses account for only 1.1 percent of the national fleet. Meanwhile, ETF said a news report last year indicated propane school buses make up about 5 percent of the national fleet.
Diesel School Buses to Further Benefit from Federal Rulemaking, Funding?
The school bus and larger commercial truck industry await a new final rule on 2027 NOx and PM levels from the EPA, which is expected this summer. EPA is also expected to announce the return of the five-year, $5-billion Clean School Bus Program, which has been on hiatus since January of last year. The agency indicated in an RFI published earlier this year that it was considering adding biodiesel and renewable diesel as fundable fuel types.
“If we get back to the idea that an EPA program on school buses is to bring the most benefit to the most school districts to make school bus emissions cleaner, using renewable fuels ranks high on the list of accessible and affordable and good options,” Schaeffer, told School Transportation News.
Additionally, Congress is currently debating increased funding through the Diesel Emissions Reduction Act. Senate bill 2235 and would also increase spending to $100 million for each fiscal year 2026 through 2029, according to the Congressional Budget Office. H.R. 2140 contains the same spending amounts and remained in the Energy and Commerce committee.
An online STN survey of transportation directors conducted in April indicated that only 11 percent of 193 respondents are prioritizing electric or alternative school bus purchases for the upcoming school year compared to the previous school year. Diesel school buses also continue to be the most common fuel type, according to registrants of next month’s STN EXPO West conference who are signed up to attend the Transportation Director Summit.
Related: Survey: Half of School Districts Paying At Least 6% More for Diesel
Related: Propane Grabs Spotlight as Fleets Seek Less Expensive, Cleaner Fuel
Related: Engine, Truck Manufacturers Support EPA Easing Derate of SCR Diesel Emissions Controls
Still, some school districts are maintaining previous plans to phase out diesel and expand electric and propane school bus purchasing. Cypress-Fairbanks Independent School District in the Houston, Texas area — the largest school bus operation in the state — has no current plans to purchase diesel school buses as it focuses on propane and electric, said Bobby Williams, assistant director of transportation for fleet maintenance.
He said propane now represents 41 percent of the district’s fleet, with diesel coming in second at 34 percent.
Pittsburg Unified School District near San Francisco, California, operates a small fleet of 33 buses, with nine powered by renewable diesel.Matthew Belasco, the district’s director of transportation, cited California’s 2035 mandate to transition to zero-emissions school buses as a leading reason why fellow districts have moved away from diesel, despite technically still being able to purchase them for the next nine years.
The district currently operates seven electric school buses and 17 propane.
“Most state and federal funding programs have been focused on supporting zero-emission and, in some cases, low-emission alternatives, like propane,” he added. “We got some funding for propane a few years ago. Generally, though, districts that seem to be looking to replace buses have moved toward electric or propane options.”
The post Diesel School Buses Continue Market Domination Amid Move Toward Lower-Emission Alternatives appeared first on School Transportation News.




Ty Estes is the Marketing Director for Hytera US, Inc., where he oversees promotion of the company’s radio communication products. Ty has over twenty years of experience in marketing wireless communications and network technologies, and he has chaired committees in telecommunications trade associations and authored several technical papers. Ty has a bachelor’s degree in English from California State University, Long Beach.
) system that connects and coordinates people, vehicles, and operations in real time. In the $50 billion student mobility market – the largest segment of the mass mobility industry – Zum CMX is transforming a daily source of anxiety and disruption into a reliable, transparent, and efficient mobility experience for students and families. Today, more than 4,500 schools rely on Zum CMX. Recognized globally for its innovative approach and operational execution, Zum has been named to Fast Company’s World’s Most Innovative Companies, CNBC Disruptor 50 and Changemakers, the World Economic Forum, and the Financial Times’ Fastest Growing Companies lists. Zum is backed by leading investors including Sequoia Capital, GIC, SoftBank, and TPG. Zum, Zum CMX, and associated logos are trademarks of Zum Services, Inc. All rights reserved. Learn more at