Improving the efficiency of tractor-trailers is critical to reducing air pollution and climate impacts in the transportation sector. There are a number of different strategies for reducing fuel use and CO2 emissions from these long-haul trucks; this paper focuses on technologies for increasing trailer efficiency, primarily by reducing aerodynamic drag, rolling resistance, and weight. And while heavy-duty vehicle efficiency is a global issue—in many countries, on-road freight is the fastest-growing source of transportation-related fuel consumption and greenhouse gas (GHG) emissions—this study concentrates on the United States, which is poised to revise and expand the HDV efficiency standards it first established two years ago.
In the U.S., two primary programs have targeted trailer efficiency. The Environmental Protection Agency’s voluntary SmartWay Transport Partnership has since 2004 spearheaded a number of initiatives focused on verifying trailer technology performance and disseminating information. And California's heavy-duty vehicle greenhouse gas rule, governing tractor-trailers operating in that state, includes provisions for both aerodynamic and rolling resistance improvements to be phased in between 2010 and 2020.
When the EPA and the National Highway Traffic Safety Administration were finalizing the first GHG and fuel-efficiency standards for medium- and heavy-duty vehicles in 2010–2011, the agencies acknowledged the substantial fuel savings to be achieved from improvements to trailers. Nevertheless, they declined to include trailers in that "Phase 1" rule, citing time constraints and the need to reach out to the trailer industry.
Phase 2, soon to begin, presents an opportunity to capture the efficiency gains offered by trailer technology improvements. This study outlines the range of options and offers some specific recommendations for the upcoming U.S. rulemaking.