Evaluation of Duty cycles for Heavy-Duty Urban Vehicles
Three laboratories, VTT, Environment Canada and West Virginia University measured standard size urban buses driving various duty cycles on chassis dynamometers. Both European and North American diesel and natural gas vehicles were represented. Environment Canada performed a comparison of a conventional diesel vehicle and a diesel-electric hybrid vehicle. The fuel consumption and exhaust emissions varied not only by test cycle, but also by vehicle technology. In the most cases, vehicles emissions can be directly proportioned to the amount of fuel consumed. However, NOx-emissions from SCR-vehicles form an exception, as well as particle emissions from vehicles producing very low absolute particle emission levels. Scaling factors to be used for comparing emission results generated with different duty cycles were developed. Most of the evaluated test cycles provide coherent fuel consumption and emission results. Some specific test cycles result in abnormalities, and must therefore not be considered representative for buses.