Heavy-Duty Vehicle Characteristics in Tennessee - For Use in MOBILE6

摘要

Heavy-duty vehicle (HDV) categories used for modeling emissions in the MOBILE6 model have been expanded from a single category in MOBILE5 to eight categories in MOBILE6. Truck registration data for Tennessee have been analyzed to determine the numbers of vehicles in each category and the age distribution of the vehicles for comparison to national default values in MOBILE6. The new categories are based on vehicle weight (e.g. HDV2B vehicles have a GVWR (gross vehicle weight rating) of 8500 to 10,000 lbs, HDV8B have a GVWR greater than 60,000 lbs. The heavier vehicles have higher emissions, so it is important to use correct vehicle weight category distributions. Tennessee's heavy-duty vehicle registration data show a distribution very similar to the national defaults, but with more vehicles in the heaviest weight category HDV8B. More than 50% of Tennessee's HDV's fall in the lightest vehicle category HDV2B. The two biggest differences in truck characteristics in Tennessee versus national defaults in MOBILE6 are the age of HDV8B vehicles, and the higher HDV fraction on Tennessee rural interstates. The national default age distribution shows a median vehicle age of 9 years for HDV8B vehicles. The Tennessee registration data shows a median age of only 5 years for HDV8B vehicles. This age difference in vehicle age distribution causes a 20% reduction in VOC emissions, a 40%) reduction in CO emissions, and a 33%) reduction in NOx emissions from HDV8B vehicles to be predicted with MOBILE6 for 2010. The paper presents a detailed breakdown of the characteristics of the Tennessee HDV fleet compared to national defaults in MOBILE6.