Literature review: Real-world fuel consumption of heavy-duty vehicles in the United States, China, and the European Union

In contrast to passenger cars, data on HDV fuel efficiency are not readily available. That is the primary motivation for this literature review, which provides a summary of recent data on real-world fuel consumption of HDVs—specifically, tractor-trailers—in three regions: the United States, China, and the European Union. The primary objectives of the study are:

1. To provide a brief overview of the market and fleet characteristics of tractor- trailers in the U.S., China, and the EU and discuss the policy measures enacted in each region to promote increased HDV fuel efficiency
2. To describe the various types of fuel consumption data and their usefulness in assessing the impacts of fuel efficiency and GHG regulations
3. To synthesize all of the publically available real-world fuel consumption data in each region and illustrate the widespread lack of data across jurisdictions and underscore the need for further data collection and research in this area
4. To lay the foundation for future research that can more thoroughly analyze how the rates of fuel-saving technology deployment differ from region to region and how this translates into differing rates of efficiency improvement over time

The study made use of national or regional fuel consumption data, aggregate data across a number of fleets, road-test data for individual vehicles, and chassis dynamometer data. The data available in each category for each region varied widely, and there is a general scarcity of data on real-world fuel consumption of tractor-trailers. The study found the largest number of publicly available sources for the U.S., followed by the EU, with China having very few sources to reference other than chassis dynamometer results.

The study found that in the U.S., average tractor-trailer fuel consumption rates for the entire fleet are approximately 39 L/100 km (6 mpg). For the newest U.S. models, fuel consumption is typically between 33 and 36 L/100 km (6.5–7 mpg). A fleet-wide analysis done for the European Commission estimates tractor-trailer fuel consumption at roughly 31 L/100 km, while tests of individual vehicles done by trucking magazines suggest somewhat higher average rates of consumption at approximately 36 to 38 L/100 km. At present, there is not sufficient information to say definitely if the U.S. or EU has more efficient trucks. However, because the U.S. has mandatory HDV efficiency standards in place, the rate of technology development and deployment will likely be faster than for trucks in the EU, which does not currently have performance standards in place.

Chassis dynamometer testing performed as part of the regulatory development process in China reveals that tractor-trailers seem to have much higher fuel consumption rates, on average, than in the U.S. and the EU. These laboratory results yield an average of 44 L/100 km.

Limited data availability, as well as the myriad of region-specific variables that influence real-world fuel efficiency—such as driver behavior, average speeds, payloads, and environmental conditions—make it difficult to perform an apples-to-apples comparison of fuel-consumption rates across the three regions. This study calls attention to the significant need for additional data collection and sustained inventory campaigns for vehicle fuel use and activity that can allow government, industry, and other stakeholders to better understand the real-world impacts of fuel efficiency and GHG regulations for HDVs.