U.S. Passenger Vehicle Fleet Dirtier After 2008 Recession

MTorrice writes The 2008 recession hammered the U.S. auto industry, driving down sales of 2009 models to levels 35% lower than those before the economic slump. A new study has found that because sales of new vehicles slowed, the average age of the U.S. fleet climbed more than expected, increasing the rate of air pollutants released by the fleet.

In 2013, the researchers studied the emissions of more than 68,000 vehicles on the roads in three cities—Los Angeles, Denver, and Tulsa. They calculated the amount of pollution released per kilogram of fuel burned for the 2013 fleet and compared the rates to those that would have occurred if the 2013 fleet had the same age distribution as the prerecession fleet. For the three cities, carbon monoxide emissions were greater by 17 to 29%, hydrocarbons by 9 to 14%, nitrogen oxide emissions by 27 to 30%, and ammonia by 7 to 16%.

Comments

Only part of the equation

[ebrandsberg]

The question is if replacing the fleet would have triggered production based pollution that offset any gains. Making new cars isn't a pollution free activity after all. The net result may have been a reduction in worldwide pollution instead.

Dirtier than a hypothetical, not an actual

[michaelmalak]

From the actual abstract:

Using fleet fractions from previous data sets, we estimated age-adjusted mean emissions increases for the 2013 fleet to be 17–29% higher for carbon monoxide, 9–14% higher for hydrocarbons, 27–30% higher for nitric oxide, and 7–16% higher for ammonia emissions than if historical fleet turnover rates had prevailed.

The article shows that the actual 2013 fleet is dirtier than the hypothetical 2013 fleet where the age distribution matches the 2007 fleet age distribution.

It does not show that the actual 2013 fleet is dirtier than the actual 2007 fleet. It's a question not addressed by this study, but I would be surprised if actual 2013 was dirtier than actual 2007.