Study finds 2008 recession contributed to increase in age of US LDV fleet, slowing of emission reductions
29 December 2014
The global economic recession of 2008—which severely depressed light-duty vehicle sales—resulted in an increase in the age of the light-duty vehicle fleet in the US that likely slowed the rate of decrease of fleet average emissions, according to a study by Gary Bishop and Donald Stedman at the University of Denver.
In general, on-road vehicle fleet emission factor increases are correlated with increasing age. Over the last two decades in the US, US owners have been keeping their vehicles longer as vehicle prices and reliability have increased, leading to a “slow and steady” increase in the average age of the registered US fleet from approximately 8.5 years old in 1995 to just over 11 years old in 2012, the authors note in their paper, published in the ACS journal Environmental Science & Technology.
The 2008 recession exacerbated this trend; nationwide light-duty vehicles sales for 2009 models were 21% less than in 2008 and 35% less than 2007 pre-recession levels—the fewest new vehicles sold in the United States since the early 1980s.
New vehicle sales, or lack thereof, have a cascading effect on the overall vehicle fleet with delayed purchasing decisions impacting the number of vehicle retirements, which in turn changes not only the age of the on-road fleet but can also alter its emissions profile.
—Bishop and Stedman (2014)
In the study, the authors used collected on-road emission measurements from sites in three western United States cities—Denver, Los Angeles and Tulsa—to highlight some of the changes in the on-road fleet’s age distribution and to estimate the implications on the fleet’s emissions.
A remote vehicle exhaust sensor (Fuel Efficiency Automobile Test, FEAT), developed at the University of Denver, collected the data sets. The instrument consists of a source and detector unit aligned across a single lane roadway and consists of a non-dispersive infrared (NDIR) component for detecting CO, CO2, HC, and twin dispersive ultraviolet spectrometers capable of measuring nitric oxide (NO), sulfur dioxide (SO2), ammonia (NH3), and nitrogen dioxide (NO2) at 100 Hz.
FEAT measures vehicle exhaust gases as a ratio to exhaust CO2 because the path length of the plume is unknown, and the ratios are constant for a given exhaust plume.
A freeze-frame video image of the license plate of each vehicle was recorded along with the emission measurements. The license plate information was used to obtain non-personal vehicle information including make, model year, and vehicle identification number (VIN) from the state registration records for California, Colorado, and Oklahoma. The VIN information was further decoded for vehicle type (passenger or truck) and fuel type for the Oklahoma records.
In addition to emission measurements, a pair of parallel infrared beams 6 feet apart and approximately 2 feet above the roadway measured the speed and acceleration of the vehicles. Measurements were only collected during daylight hours with dry roadway conditions.
They found large reductions in the fleet fractions of 2009 model year vehicles of 40% (Denver), 38% (Los Angeles), and 35% (Tulsa), respectively, when compared to pre-recession 2007 levels; the light-duty truck category suffered the largest percentage declines. This resulted in a significant increase in the on-road freeway fleet age, which had been relatively stable; the fleet average age increased by two years in Denver and Los Angeles but only by one year in Tulsa, likely due to its faster economic recovery, the authors sugested.
Using fleet fractions from previous data sets, they 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 been maintained.
Resources
Gary A. Bishop and Donald H. Stedman (2014) “The Recession of 2008 and Its Impact on Light-Duty Vehicle Emissions in Three Western United States Cities” Environ. Sci. Technol., 48 (24), pp 14822–14827 doi: 10.1021/es5043518
A long service life has long been one of the attractive characteristics of US-built vehicles, just ask the Cubans, so if that is increasing, perhaps it is something to celebrate rather than condemn. After all, does it not also mean that the energy, emissions and raw materials consumed in their production are amortised over a longer period? And If I understand it correctly, the USA has regular emissions tests for all vehicles, which should ultimately weed out the most serious cases of exhaust emissions.The planned obsolescence for which Detroit was notorious during the 1950's is a policy which over-zealous emissions standards, focussing on vehicle age, could all too easily re-introduce.
Posted by: Peterww | 29 December 2014 at 04:18 AM
If they want more EV adoption, they should help families that cannot normally afford to purchase one do so. This business of offering tax credits, only helps people who actually pay that much in federal taxes. Offering rebates off of the front end could really help, because people would have a better chance of getting better financing.
As for a new vehicle purchase, its looking like ill have to make my current car last till 2017, it'll be 15 when replaced(2002).
Hopefully, ill be able to purchase a plugin hybrid SUV, or something else groundbreaking
Cars, if it weren't for the elements and crashes would probably last 20+ years if the owners would maintain them. Sadly, older cars are on the road and often not properly cared for, resulting in higher emissions, and reduced safety.
With aluminum and an autonomous driver, we could probably expect cars to last 20 years, stricter California emissions in most states would keep most polluters in line. And mandatory safety checks performed by states hopefully would keep everyone on the road safe as possible. It kills me when I see new drivers in cars without functioning brakes, doors, tires, lights, etcetera.
Posted by: CheeseEater88 | 30 December 2014 at 06:29 AM