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Study: Passenger Vehicle Fleet is Older and More Polluting

Arguably just as important than the sales of new vehicles, e.g., hybrids and EVs, are the consequences of not buying new cars.
December 14, 2014, 11am PST | Irvin Dawid
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Janet Pelley of Scientific American and Chemical & Engineering News write about the environmental consequences of holding on to our motor vehicles too long. A new study from the University of Denver, published Nov. 28 in Environmental Science and Technology, "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."

On the basis of remote sensing data, the scientists determined that the mean age of the 2013 fleet was nine years old. For nearly two decades before the recession, the average age had remained stable at seven years old.

  • With remote sensing, "a remote exhaust detector shoots infrared and ultraviolet light across the road to sensors on the other side. As cars pass through the beam, the sensors measure levels of pollutants in the exhaust plumes."
  • "Remote sensing offers all of the advantages and none of the drawbacks of centralized, drive-in [smog] tests," according to the National Motorists Association

The age of the fleet is important because older cars lack the sophisticated emissions-control technology installed on newer vehicles to meet newer, tougher emission standards. The authors note:

  • "The age distribution of the vehicle fleet is an important variable that scientists use in their models to determine if emissions regulations will deliver on promises of cleaner air, says Gary A. Bishop, an atmospheric scientist at the University of Denver and lead author of the study."
  • If drivers buy newer, cleaner cars, then older, dirtier ones get taken off the road, and air quality improves."

When it comes to air pollution, transportation is the leading source. According to the Environmental Protection Agency (EPA), "motor vehicles are responsible for nearly one half of smog-forming volatile organic compounds (VOCs), more than half of the nitrogen oxide (NOx) emissions, and about half of the toxic air pollutant emissions in the United States."

Conclusion: Because drivers haven't replaced older car with newer cars like they did prior to the recession, the researchers "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."

Note from Scientific American: "The article is reproduced with permission from Chemical & Engineering News (© American Chemical Society). The article was first published on December 11, 2014."

Correspondent's note: For older cars and/or vehicles unable to pass smog tests, air quality regulators recommend that motorists consider so-called buy back (also called retirement or scrappage) programs to permanently remove them from the passenger vehicle fleet. Here are two such programs from the Bay Area Air Quality Management District (BAAQMD) and the California Air Resources Board (CARB).

  1.  To reduce air pollution, the BAAQMD Vehicle Buy Back Program will pay $1,000 for an operating and registered 1994 and older vehicle.

  2. According to CARB, "the (state) program is administered by the Bureau of Automotive Repair and provides $1,000 per vehicle and $1,500 for low-income consumers for unwanted vehicles that have failed their last Smog Check Test and that meet certain eligibility guidelines. The purpose of these programs is to reduce fleet emissions by accelerating the turnover of the existing fleet and subsequent replacement with newer, cleaner vehicles.  Reducing emissions from the existing fleet is a component of California’s State Implementation Plan (SIP), which outlines the State’s strategy for meeting health-based ambient air quality standards."

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Published on Friday, December 12, 2014 in Scientific American
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