|Fuel economy for last 30 years|
Despite improvements in the efficiency of technologies, model year 2005 light-duty vehicles in the US are estimated to average 21.0 mpg, eking out just a 0.2 mpg improvement over 2004, according to the EPA.
The data, published in the just-released annual report on automotive technology and fuel economy trends, highlights that fuel economy has been essentially flat for the past dozen years, although the size and power of the vehicles sold has increased dramatically.
In other words, the efficiencies of new technology are applied to creating vehicles (in an aggregate view) with roughly equivalent fuel consumption, but that are bigger and more powerful.
|Vehicle weight in tons times fuel economy|
The chart to the right (Click to enlarge) plots the ton-mpg (weight in tons times fuel economy) of vehicles since 1975.
Improvements in actual fuel economy of light-duty vehicles peaked in 1987 at a combined average 22.1 mpg, and has since declined some 5% due both to the increasing size and power of vehicles in each succeeding model year, and to the increasing mix of trucks and SUVs in the fleet.
On the basis of ton-mpg, however, improvements have been steady over the past 30 years, rising from an average 26.9 ton-mpg in 1975 to 43.2 ton-mpg in 2005. (There is also less of a gap, as you might expect, beween cars and trucks when viewed on this basis.)
|Vehicle Weight and Acceleration|
Another view of the situation comes from the next chart (at right, Click to enlarge) that plots vehicle weight and acceleration time for the model years 1975 through 2005.
Reductions in weight and power, and increases in fuel economy, all maximized in response to the series of oil crises in the 1970s and early 1980s that culminated with the Iranian revolution.
Since then, we have steadily moved back toward heavier, more powerful vehicles, although advances in vehicle and engine technology managed to maintain the baseline fuel economy gains made during the 1980s.
Objectively, that level of fuel economy is grossly inadequate, given the geopolitical, geological and environmental constraints and issues we face today.
Ironically, the report comes right when the House and Senate are voting on a consolidated version of the energy bill—a bill that makes no quantitative advances in fuel economy regulations and that neglects short-term initiatives that could substantially alter that figure.