Vehicle characteristics and emissions: Logit and regression analyses of I/M data from Massachusetts, Maryland, and Illinois

This research extends earlier studies on the relationships between vehicular emissions and characteristics, with a particular focus on the effects of fuel economy, vehicle make and maintenance, and seasonal factors, on emissions of carbon monoxide, hydrocarbons, and nitrogen oxides. Nearly 4 million records of data derived from the 2001 inspection and maintenance (I/M) programs in Illinois, Maryland, and Massachusetts, are used to estimate logit models of test failures and regression models of vehicle emissions. Vehicle age, fuel economy, mileage, engine characteristics, weight, make, general maintenance, and time of year are found to be strong determinants of emissions and test failure rates. The emission models estimated with the Massachusetts data show broad variations in the effects of the independent variables across makes, for both cars and trucks.