Fuel-Based On-Road Motor Vehicle Emissions Inventory for the Denver Metropolitan Area

Emission inventories from mobile sources have traditionally been obtained through computer modeling. This method, however, has intrinsic shortcomings in that ideal factors are included while real-world observations are left out. The model predictions have not correlated well with measurements from several studies. Recently, a fuel-based method of obtaining on-road emissions inventories has been developed. This technique calculates emission factors in grams of pollutant per unit of fuel used (kg, gallons or L) from remote sensing measurements. Combining these factors with fuel use data, available from tax records, yields a fuel based emission inventory. We have used this routine to calculate the CO, HC and NO on-road emissions inventories for the Denver Metropolitan area during several years when the enhanced I/M program has been in place. Our calculations indicate that the inventories are smaller than predicted by the MOBILE5b model and that emission reductions are not as extensive as modeled.