Diesel is the predominant technology in commercial trucking, school, and transit bus sectors, according to the Diesel Technology Forum’s analysis of data sourced from S&P Global Mobility TIPNet data of vehicles in operation for Class 3-8 as of December 2021.

This analysis found the following:

Commercial Trucks: 76% of the approximately 15 million commercial trucks (Class 3-8) that make up the nation’s fleet run on diesel. Of those, the newest generation of advanced diesel technology models now account for 53% of that fleet.

Other fuels that play a role in commercial trucking include gasoline (23%) and compressed natural gas (0.4%). Electric and other categories each register less than 1%.

Of the largest trucks (Class 8) in operation, 97% are diesels. About 32% of all electric trucks nationwide are in California, where for every electric truck there are about 300 diesel trucks (all years, Classes 3-8). Nationwide, for every electric commercial truck in operation, there are 995 trucks powered by diesel.

Last year, Indiana had the largest number of new-generation diesel trucks registered (69.3%), followed by Utah (63.2%), Pennsylvania (62.8%), Texas (60.1%), Oklahoma (60.0%), Florida (59.1%), the District of Columbia (58.4%), Illinois (56.2%), Maryland (55.7%), and Wisconsin (55.5%).

For the largest commercial trucks (Class 8), 62.5% of diesels on the road are 2007—meaning they are equipped with at least a diesel particulate filter. For gasoline vehicles that make up about a quarter of all commercial trucks (Class 3-8), more than half (57.5%) of those in operation are 2007 and newer model years.

The significance of the model years (2007 and 2010 and later MY) relates to emissions standards and the introduction of new emissions controls such as particulate filters, oxidation catalysts, and selective catalytic reduction systems. This enables new diesel engines to achieve near-zero emissions with increasing fuel efficiency and lower carbon dioxide (CO₂) emissions.

In previous research commissioned for DTF, AutoForecast Solutions found that increasing the number of advanced diesel technology trucks on the road will eliminate more than 1.3 billion metric tons of CO₂ during this decade.

Source: Diesel Technology Forum

School Buses: 91% of the approximately 500,000 school buses run on diesel power. Other fuels that play a role in pupil transportation include gasoline (4%) and other fuels (5%). Electric and compressed natural gas each register less than 1%.

Of the diesel portion of the current school bus fleet, approximately 72% of all buses in operation have at least particulate trap technology and 58% are of the newest generation of advanced diesel technology equipped with both particulate filters and selective catalytic reduction systems.

Transit Buses: 79% of all non-school (transit) buses in operation are powered by diesel, 10% compressed natural gas (CNG), electric (6%), other (5%) and gasoline (0.1%). The “other” category includes hybrid diesel electric as well as propane-powered buses.

For the diesel portion of the current fleet, about 59% of transit buses are at least equipped with particulate trap technology and 47% are the newest generation of advanced diesel technology equipped with both particulate filters and selective catalytic reduction systems.

New Jersey is the state that added the most new-generation diesel buses in 2021 (more than 300) compared to the previous year. Washington D.C. saw a 15.3% increase in number of new diesel buses put in service (2021 vs. 2020).

The Diesel Technology Forum is a not-for-profit organization dedicated to raising awareness about the current and future role of diesel engines, equipment, and fuels. Forum members are leaders in advanced diesel technology, emissions controls, as well as petroleum-based and renewable biofuels.