DOE OSTI2012
Medium- and heavy-duty trucks and buses are responsible for over 28% of the energy used and emissions generated in highway transportation, and class 8 tractor-trailers operating in long-haul and regional cargo transport are responsible for about 75% of all fuel consumed by commercial trucks. The vehicle miles traveled (VMT) for trucks is expected to increase at a rate significantly outpacing passenger VMT growth, which will result in a steady rise in the percentage of energy consumption (and emissions) attributable to trucks over the coming decades. These facts have sparked significant recent interest in truck fuel efficiency in the transportation community. Although fuel economy regulations in the United States have historically focused on passenger cars, recent legislation requiring new standards for fuel economy in medium- and heavy-duty trucks aims to increase the efficiency of trucks as well. The development of regulations for truck fuel efficiency is quite challenging, however, since vehicle usage and configurations vary substantially among the very diverse set of trucking applications. Fuel economy is very strongly linked to the particular drive cycles followed by a given truck, as are the gains in efficiency that can realized by implementing new technologies. As demonstration of this fact, a technology that provides significant fuel efficiency gains for one trucking application may yield little improvement or could even be detrimental to fuel economy in a different trucking application. It is therefore critical that the usage of each application be well understood and carefully evaluated to select the set of technologies that can provide the greatest benefits for each application. Although it is well known that drive cycle data representative of a vehicle or fleet’s usage is crucial for an accurate evaluation of fuel economy benefits or to identify an optimum set of technologies to reduce fuel consumption, detailed drive cycle data of trucks are not readily available for many applications. The Oak Ridge National Laboratory (ORNL) has collected a rather extensive set of truck duty cycle data in an effort to characterize the usage of several trucking applications. During the first phase of ORNL’s duty cycle data collection activities, drive cycle measurements were made from six tractor-trailers during normal operations in a regional commercial shipping fleet, operating primarily in the southeastern U.S., for a period of a full year. This data, contained in the Heavy Truck Duty Cycle (HTDC) project database, was analyzed in detail for the current research effort in the Truck Technology Efficiency Assessment project. Based on the high fidelity HTDC duty cycle data, the results of this study are therefore highly representative of tractor-trailer operations for this type of regional, freeway-dominant trucking application.