Simplified methodology to estimate emissions from mobile sources for ambient air quality assessment

Vehicle emissions from mobile sources are major contributors to air pollution and air quality degradation in the United States. The inventory of these emissions is a key component in ambient air quality assessment and air pollution abatement strategies. Procedures for preparing the mobile source emission inventory require complex data processing and calculations. This paper presents a simplified methodology for estimating vehicle emissions based on key parameters of vehicle model year, average vehicle speed, and air temperature, which have major effects on emission rates. Simplified multiple linear regression equations are developed from a database of the EPA's MOBILE6 computations to calculate emission factors. The coefficient of determination (R-2) values of the models range from 0.82 to 0.99. The methodology has been implemented in Mississippi and validated for rural areas in Ohio. The methodology is applicable to other areas in comparable geographical regions with similar traffic volume and fleet mix. The results of vehicle emissions show good correlation with daily ground-level ozone variations and can be effectively used for ozone modeling and air quality assessment.