A rough estimate of average gasoline use per mile traveled, a measure of the efficiency of the in-use vehicle fleet, can be obtained by dividing total gasoline consumption reported by EIA by preliminary total highway miles travelled reported by the Federal Highway Administration. Based on this measure, the implied average fuel efficiency of the in-use light-duty vehicle fleet rose by roughly 1.1 percent in the first half of 2012 versus the comparable year-ago period. Efficiency gains likely reflect both increasingly stringent Corporate Average Fuel Economy (CAFE) standards that were implemented for light-duty trucks starting in model year 2008 and for passenger cars starting in model year 2011 and consumer vehicle choices in an era of higher gasoline prices.
The net effect of the income, price, and fuel efficiency impacts as modeled by EIA implies almost flat year-over-year gasoline consumption. Keeping in mind that measures of freight activity suggest some actual decline in the light-duty vehicle share of total vehicle travel between the first half of 2011 and the first half of 2012, the STEO modeling appears to be roughly consistent with, the 0.3-percent year-over-year decline in gasoline use reflected in EIA's current data for January through June 2012.