Research carried out at the University of Michigan suggests that motorisation in the US may have peaked.

The research has found that the percentage of American households without a vehicle has increased nearly every year since 2007.

Following up his research from last year showing that Americans own fewer light-duty vehicles per household, drive them less and consume less fuel than in the past, Michael Sivak of the U-M Transportation Research Institute examined recent trends (2005-12) in the proportion of US households without a car, pickup truck, SUV or minivan.

He also studied variations in this proportion for the 30 largest US cities for 2007 and 2012.

Sivak found that 9.2% of US households were without a vehicle in 2012, up from 8.7% in 2007. Further, the proportion of such households increased in 21 of the 30 largest cities, with the 13 cities with the largest proportions showing an increase during that time.

"The proportion of households without a vehicle is likely influenced by a variety of factors," said Sivak, a research professor at U-M. "Examples of such factors include the quality of public transportation, urban layout and walkability, availability and cost of parking, income and price of fuel."

According to Sivak, more than half the households in New York City had no vehicle in 2012 (56%) and at least a quarter of households in seven other US cities were without a vehicle in 2012: Washington, D.C. (38%), Boston (37%), Philadelphia (33%), San Francisco (31%), Baltimore (31%), Chicago (28% and Detroit (26%).

US households without a vehicle (%)

Year Percentage

2005 8.87

2006 8.78

2007 8.72

2008 8.84

2009 8.90

2010 9.01

2011 9.29

2012 9.22