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This paper reviews fuel-saving technologies for commercial trailers, provides an overview of the trailer market in the U.S., and explores options for policy measures at the federal level that can promote the development and deployment of trailers with improved efficiency. For trailer aerodynamics, there are many technologies that exist and are in development to target each of the three primary areas where drag occurs: 1) the tractor-trailer gap, 2) the side and underbody of the trailer, and 3) the rear end of the trailer. In addition, there are tire technologies and weight reduction opportunities for trailers, which can lead to reduced rolling resistance and inertial loss. As with the commercial vehicle sector, the trailer market is diverse, and there are a variety of sizes and configurations that are employed to meet a wide range of freight demands.

Advanced technology heavy-duty vehicles such as hybrids present unique regulatory challenges. Hybrids employ an additional energy source in conjunction with an internal combustion engine for motive power, and the interactions between the engine and the hybrid components affect criteria pollutant emissions and fuel consumption. Often, an engine installed in a hybrid vehicle will operate very differently from the same engine installed in a conventional vehicle driven over the same route. One of the difficulties in integrating vehicles such as hybrids into regulatory programs is developing the proper certification test procedures for criteria pollutant and greenhouse gas (GHG) emissions so that these advanced technologies and vehicles are evaluated fairly and consistently as compared to their conventional counterparts. This paper seeks to inform policy makers of the alternatives for moving toward more holistic approaches to testing and certifying powertrain systems and complete vehicles.