Abstract The Aisin A465 6-Speed Diesel Hybrid powertrain started production in early 2012 and is available in the North American market in the Hino 195h DC COE truck. The suitability, and added fuel efficiency, of a Hybrid powertrain for Class 5 Box truck is very dependent on fleet usage conditions and duty cycle. Aisin has undertaken real- world, extended mileage, durability testing on public roads to determine the operational modes for which such a powertrain is most suitable, and for which a fleet owner can expect fuel savings that will result in a payback period justifying the higher cost of a hybrid system equipped commercial truck. Data collected on the same Aisin proprietary durability test routes with a Conventional Class 3-5 Cab Chassis truck provides insights into truck usage parameters that dif fer between Hybrid and Conventional Class 3-5 commercial trucks. Comparison of relevant portions of the standardized test cycle illustrates operating advantages and short-comings of the two powertrains, and allows for the development of vehicle test methods to evaluate future Hybrid powertrain configurations for Commercial Trucks in this class for suitability for a given intended duty cycle and understand the potential return on investment on the added hybrid system cost. Introduction Aisin Seiki, an Aisin group company, is a leading manufacturer of commercial-duty automatic transmissions, in addition a wide variety of automotive components and systems for all classes of on-road vehicles. The Aisin Technical Center of America (ATCA), in Northville MI, has development responsibility for North American OEM products, including Class 3-5 commercial-duty automatic transmissions. In particular, the majority of vehicle system level development and validation is undertaken by ATCA (including through third-party vendors). Currently, Aisin supplies commercial automatic transmissions to Class 3-5 conventional cab pick-up and cab chassis trucks with diesel and gasoline engines, as well as Class 4 and 5 Cab Over Engine (COE) commercial trucks. This includes specifically the 155 and 195 Hino Motors line of trucks, which are available with diesel and diesel hybrid powertrain options. In real-world validation of these various products, ATCA maintains responsibility for public road evaluations of the truck and powertrain systems. For a variety of powertrain development work, Aisin has employed a customized public road test route in southern California and has collected a knowledge base of historical data for comparative purposes. A comparison of the data collected on this cycle for the Conventional Class 3-5 Diesel truck and the comparable Class 5 Diesel Hybrid provides insight into the operational modes that are advantageous to each type of powertrain. Comparisons of hybrid to conventional powertrains for passenger cars and over the road Class 8 HD trucks are relatively common, but similar comparisons for Class 3-5 trucks are not documented as frequently. Aside from the occurrence in literature of comparative studies of public road testing, medium duty commercial vehicles present challenges that are not replicated in passenger cars (and to some extent in Class 8 trucks as much). In particular, the operating weight conditions for these commercial trucks range greatly from curb weight to fully loaded, be it GVWR (Gross Vehicle Weight Rating) or GCWR (Gross Combined Weight Rating). Adequate performance and fuel efficiency when running at higher loads is crucial to commercial trucks success to the fleet owners. Test Route Description The public road course that Aisin has historically used for commercial vehicle evaluation is located in in southern California, in the cities and surrounding areas of Los Angeles, Long Beach, Ontario, Palm Springs, and Riverside. Standardization of the route allows for a fair basis for comparison between different vehicles that may have been tested at different times and Model Ye