The results of the motor-vehicle exhaust emission inventory are reported by a grid system on a map of the study area and by grids. The total amounts of pollutants (CO, HC, NOx, SOx, and particulates) emitted from motor vehicle exhausts are tabulated. Evaporative losses and crankcase emissions in the study area account for 47 percent of the total hydrocarbon emissions, and exhaust emissions compose the remaining 53 percent. Typical analysis of motor vehicle emissions was used to check these estimates. Three pollutants - carbon monoxide, hydrocarbons, and nitrogen oxides - comprise 99 percent of the total weight of exhaust emissions in the study area. Sulfur oxides and particulates generally compose the greater percentage of the pollution in an industrial-urbanized area; however, these pollutants comprise only a small portion of the total weight of exhaust emissions. These pollutants are significant because of their toxicity, particle size, and secondary reactions involving the formation of aerosols. The combined emission rate of sulfur oxides and particulates is 2,640 pounds per day. If this pollution were distributed over the 41.6 square miles that comprise the land area of the City of Gary, the emission density for these two pollutants would be 63.5 pounds per square mile as compared to the emission density for carbon monoxide of 845.9 pounds per square mile. The vehicle-mile average-speed approach is presently the most accurate method for estimating the emissions from motor vehicle exhausts. The total emission of sulfur oxides and particulates from motor vehicles is small as compared with the three major pollutants. The use of the emission factors based on the fixed-mode cycle does not, therefore, introduce much error in the total weight of pollutants. (Author)

"A study done by the Abatement and Control Programs, National Center for Air Pollution Control, for Division of Air Pollution, City of Gary, Indiana." Includes bibliographical references (p. 19)