Evaluation of duty cycles for heavy-duty urban vehicles: Final report of IEA AMF Annex XXIX

Three laboratories, VTT, Environment Canada and West Virginia University measured standard size urban buses driving various duty cycles on chassis dynamometers.The number of test cycles per laboratory varied from 6 to 16. Included in the vehicle matrix were European and North American diesel and natural gas vehicles.Environment Canada performed a comparison of a conventional diesel vehicle and a diesel-electric hybrid vehicle.Fuel consumption as well as exhaust emissions were measured.The main objective of the project was to evaluate how various duty cycles affect fuel consumption and exhaust emission figures.As could be expected, the results vary significantly not only by test cycle, but also by vehicle technology.In some cases increased fuel consumption or load results in increased emissions, in other cases reduced emissions.However, for most, vehicles emissions can be directly proportioned to the amount of fuel consumed.In this respect 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.All three laboratories performed measurements on three common cycles, the ADEME-RATP Paris bus cycle, the Orange County Transport Authority cycle and the Braunschweig bus -cycle.This made it possible to also compare European vehicles and North American vehicles with each other.However, such a comparison is only indicative, as there are differences in vehicle specifications, testing equipment and also in test procedures and testing conditions.