Heavy-duty (HD) trucks consume approximately 12% of the petroleum used in the United States. In this group, Class 8 long-haul trucks are the largest fuel users, consuming nearly two-thirds of the fuel used by all HD trucks [1]. Thus, significant effort has been devoted to developing, integrating, and deploying advanced technologies for improving HD truck performance [2–7]. This includes the US Department of Energy’s (DOE’s) SuperTruck program, which has developed and demonstrated advanced technologies for more efficient diesel engines, more durable and lighter materials of construction, hybrid propulsion systems, and auxiliary power generation and utilization. A combi- nation of technologies, spanning from powertrain to truck and trai- ler, is required to achieve the highest truck fuel efficiency. The DOE 21ST Century Truck Partnership (21CTP) Program formed by U.S. federal agencies with industrial partners has outlined six critical areas of next-generation truck technology needed to reduce fuel usage and emissions while increasing heavy vehicle safety [2]. Table 1 summarizes the 21CTP goals for each of these target areas.