As America’s commercial truck and bus fleets progress towards near-zero emissions, advanced internal combustion engines remain predominant. Gasoline, diesel, natural gas, and propane remain the primary fuel sources. According to the Engine Technology Forum (ETF), the use of advanced near-zero emissions diesel engines increased by 4% in 2023 compared to 2022.
Based on S&P Global Mobility TIPNet data, the ETF’s analysis reveals that internal combustion engines power 99.9% of the nation’s commercial vehicles. Diesel dominates with a 76% share, followed by gasoline at 22%, with the remainder comprising natural gas and propane. Meanwhile, zero-emission technologies like battery electric and fuel cell vehicles constitute a small portion of the fleet. Transit buses lead with 7.8% electric vehicles (EV), while electric-powered commercial trucks and school buses account for 20,000 and 2,000 units, respectively.
Advanced diesel trucks, particularly those from the 2010 model year onward, are equipped with the latest emissions controls, contributing significantly to reduced emissions. As of December 2023, 61% of all commercial diesel trucks on the road were of this newer generation, marking a 4% increase from the previous year. California, in particular, has seen rapid growth in advanced technology diesel vehicles, with a 13.3% increase since 2022.
Allen Schaeffer, Executive Director of the ETF, highlights the substantial environmental benefits of newer diesel technology. He notes that from 2010 through 2030, these advanced diesel trucks will save approximately 1.3 billion tons of carbon dioxide emissions and 130 billion gallons of fuel and reduce particulate matter and nitrogen oxide emissions by 1 million tons and 18 million tons, respectively. This demonstrates the critical role of ongoing investment in internal combustion engine (ICE) technology for meeting clean air and climate goals.
Renewable fuels are increasingly important in reducing emissions from the nation’s truck and bus fleets. In 2023, the US consumed over 2.8 billion gallons of renewable diesel and 1.9 billion gallons of biodiesel. Production capacity for renewable diesel is projected to reach 5.9 billion gallons annually by the end of 2025. Furthermore, more than 79% of the natural gas used in transportation in 2023 was renewable natural gas (RNG), which achieved the lowest carbon intensity score of any clean fuel option in California.
While zero-emission vehicles (ZEVs) currently make up a small fraction of the commercial vehicle population, with electric trucks at 0.1%, they are expected to play a larger role in the future. Schaeffer emphasizes that as battery electric and hydrogen technologies develop, internal combustion engines will continue to dominate goods movement and public transport sectors for decades. Continued innovation, adoption of the latest ICE technology, and expanded use of renewable fuels are essential for ongoing progress and reduction of greenhouse gas emissions.
In conclusion, America’s truck and bus fleets are steadily transitioning towards advanced, near-zero emission internal combustion engines, with significant environmental and economic benefits. The continued development and adoption of both ICE and renewable fuel technologies will play a crucial role in achieving long-term sustainability goals.
