No Wonder Fuel Economy is Stagnant, Cars Ballooned Up Since 1980


Perspective isn't the same on both photos. The new Accord is even bigger than it looks.
It's Like Our Cars Have Been Eating Fast Food for 25 Years
This isn't exactly a secret, but it's worth repeating: Our cars are getting more fuel efficient over time, the problem is that this improved efficiency is used to move around a bigger, heavier vehicle instead of being used to improve MPG. Cars keep the same nameplates, but they become completely different beasts over time...
Source: U.S. Bureau of Transportation Statistics

Christopher R. Knittel of the Institute of Transportation Studies has published a very interesting study on this. He writes:

From 1980 to 2004 the average fuel economy of the US new passenger automobile fleet increased by less than 6.5 percent. During this time, the average horsepower of new passenger cars increased by 80 percent, while the average curb weight increased by 12 percent. Changes in light duty trucks have been even more pronounced. Average horsepower increased by 99 percent and average weight increased by 26 percent from 1984 to 2004. The change within passenger cars and light trucks hides much of the story. In 1980 light trucks sales were roughly 20 percent of total passenger vehicles sales; in 2004, they were over 51 percent.

Just think of how much engines could be downsized if weight and horsepower had stayed relatively constant since 1980.

The graph above shows the changes that the Honda Accord went through since 1980. "Weight has increased by over 50 percent, while horsepower has nearly tripled! After an initial increase in fuel economy, during the run up in CAFE standards and high gasoline prices of the early 1980s, fuel economy decreased as gas prices also fell. The period of relatively constant fuel economy and increases in both weight and power illustrate that potential fuel economy gains have given way to more weight and power."

Of course some of the changes since the 1980s are good. Cleaner tailpipe emissions thanks to better emission control equipment, safer cars with airbags, stability control, bigger crumple zones, etc. But we could still have most of those benefits without anywhere near the increase in power and weight that we've seen. Many countries where fuel is more expensive than in the U.S. have much smaller vehicles that have most, if not all, of these features.

Historically, two things have had an impact on fuel economy in the US. High fuel prices, and higher CAFE standards. With oil expected to become more expensive because of higher demand when this recession ends, and Obama's new CAFE standards, it wouldn't be surprising if things started to improve more rapidly. But sadly, that's not going to be fast enough. We need bigger changes if we're to really make a difference in the CO2 emissions from transportation (BRT, light rail, bike-friendly and pedestrian-friendly cities, electric vehicles, etc).

Via Paul Kedrosky
See also: Top 10 Most Fuel Efficient Cars to Buy with "Cash for Clunkers" Money
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Tags: Fuel Efficiency | Transportation

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