Engine and Weight Characteristics of Heavy Heavy-Duty Diesel Vehicles and Improved On-Road Mobile Source Emissions Inventories: Engine Model Year and Horsepower and Vehicle Weight

Abstract

Heavy heavy-duty diesel vehicles (HHDDVs) are the major mobile emissions sources of oxides of nitrogen and diesel particulate matters; emissions rates from HHDDVs vary according to their engine and weight characteristics. By considering these characteristics, air quality management agencies can improve their mobile source emissions inventories, which serve as the cornerstone of successful regional air quality management planning. To develop on-road mobile source emissions inventories, air quality agencies use the U.S. Environmental Protection Agency's mobile emissions model MOBILE6. However, modelers cannot adjust the engine and weight characteristics of the HHDDVs because the model considers HHDDVs as a single vehicle type, with national default parameter representing their engine and weight characteristics. Georgia Institute of Technology researchers investigated the engine and weight characteristics of HHDDVs, which included engine model year, engine horsepower, and vehicle weight, through a screen-line cordon survey in the 21-county Atlanta metropolitan area. Engine model year, engine horsepower, and vehicle weight characteristics were evaluated by the chi-square goodness-of-fit test to determine whether the characteristics were homogeneous with spatial location, time period, and trip type categories. The survey indicated that the average engine age was 4.5 years and average engine horsepower was 454. However, average vehicle weight varied according to the time of day with the trip type category. Findings from this study can be used as parameters in the improvement of both accurate on-road mobile source emissions inventories and regional air quality management plans. Findings can also be used for the improvement of future on-road mobile source emissions models.