This paper presents an approach to modeling the United States truck and bus population. A detailed model is developed that utilizes domestic factory sales figures combined with a scrappage factor as a building block for the total population. Comparison with historical data for 1958-1970 shows that the model follows trends well for intermediate parameters such as total vehicle miles per year, total fuel consumption, scrappage, etc.
Fuel consumption and HC, CO, NO2, CO2 and particulate matter emissions for gasoline and diesel engines are of primary interest. The model details these parameters for the time span 1958-2000 in one-year increments. For HC and CO, truck and bus emissions could equal or exceed automobile emissions in the early 1980s, depending on the degree of control.
Three population control strategies are analyzed to determine their effects on reducing fuel consumption or air pollution in later years. It is concluded that a combination of the three strategies, substitution of diesel engines for gasoline engines in new vehicles, field retrofit of pre-1968 vehicles, and more stringent emissions restrictions would result in the greatest reductions of fuel consumption and emissions in future years.