DETROIT—The number of light vehicles on U.S. roads peaked in 2008 at 236.4 million and has been dropping since, a University of Michigan researcher contends, but the trend is expected to reverse itself in the coming years.
Researcher Michael Sivak said the decline reflects the auto industry's sharp sales slump and echoes findings from other recent reports that Americans are driving less.
Citing a variety of demographic, lifestyle and economic changes, Mr. Sivak—a research professor at the university's Transportation Research Institute—said the number of registered cars, pickups, SUVs and vans in the U.S. dropped by another 2.6 million by 2011 to 233.8 million.
He blames the recession for the decrease in light-vehicle population and suggests that the number of registered light vehicles will rise again, noting this was likely only a temporary maximum and the decline after 2008 “was primarily driven by the current economic downturn that started that year.
“Consequently, with the improving economy and the expected increase in the U.S. population, it is highly likely that from a long-term perspective, the absolute number of vehicles has not yet peaked.”
It is the latest report showing Americans have been driving less in recent years. Citing government figures that the total miles per capita driven by Americans have fallen each year since 2004, the U.S. Public Interest Research Group in May went so far as to declare the end of the nation's driving boom that dates to 1964.
The research group's study said the decline in per-capita vehicle travel began before the recession and suggested that demographic changes, high costs and shifts in consumer preferences are to blame for the drop in driving.
U.S. new light-vehicle sales topped 16 million units from 1999-2007 before falling to 13.2 million in 2008 and 10.4 million in 2009.
The number of light vehicles per person, per licensed driver and per household reached their most recent high in 2006, according to Mr. Sivak's research.
In 2011, there was 0.75 vehicle per person, down from 0.79 in 2006, while the number of light vehicles per licensed driver dropped to 1.1 in 2011 from 1.16 in 2006.
Among individual U.S. households, the number of cars and light trucks has fallen to 1.95 in 2011 from 2.06 in 2006, according to the data.
In addition to the recession and spike in U.S. unemployment, which undermined commuting, Mr. Sivak said the declines may reflect increases in telecommuting and wider use of mass transit.
The decline in driving and light-vehicle ownership rates also may be the result of a drop in licensed drivers. The research group's study reported that the percentage of driving-age Americans fell to 86 percent in 2011, a 30-year low and down from 90 percent in 1992, an all-time high.
It also noted that only two-thirds of 16- to 24-year-olds were licensed drivers in 2011, the lowest rate since 1963.
The report pointed to strict laws in 49 states that limit the abilities of young drivers as a possible cause for the drop in numbers.
After steadily rising for years, the number of vehicle miles traveled on American roads has remained relatively flat, and in some years has dropped, since 2008, Department of Transportation figures show.
Vehicle miles traveled grew in the range of 4 percent in the 1980s, dropped to a rate of 2.5 percent in the 1990s and fell to around 1 percent in the early 2000s before leveling off or falling in recent years.
Mr. Sivak's research covers road-safety trends, economic influences on vehicle-purchasing decisions and on road safety, interactions of safety and environmental countermeasures, demographic changes among drivers, eco-driving strategies and monthly monitoring of vehicle fuel economy and emissions, according to his biography on the university's website.
This report appeared on the website of Automotive News, a Detroit-based sister publication of Tire Business.