Comparison of EPA and Inuse Fuel Economy Results for 1974 - 1978 Automobiles - An Analysis of Trends

The DOE inuse fuel economy data base was enlarged through the addition of data for 1978 as well as previous model years. A covariance analysis was used to identify variability among individual data sources. The analysis indicated that the variation among sources was small relative to the variation within individual sources and the sources pooled by model year.

A unweighted linear regression in gallons per mile space was determined to be appropriate for evaluating the impact of the EPA to onroad relation on attainment of fuel economy standards and projection of fuel demand. The resulting model year relations did not significantly differ over the 15 to 25 mpg range. The data for the five model years were pooled, and a common regression was calculated. The regression relations, both model year and pooled model years, were analyzed for trends in shortfall as a function of mpg and time. The results of this analysis were compared to those of other studies and used to project the impact on fuel demand.