Americans drove 9.6 billion fewer miles in May compared with the same month a year ago, data showed Monday, with officials blaming high petrol prices.
The figure represents the largest year on year decrease in driving for May since the Federal Highway Administration (FHA) began compiling statistics 66 years ago, the agency said.
"This is the largest drop in vehicle miles travelled for any May, which typically reflects increased traffic due to Memorial Day vacations and the beginning of summer," the FHA said in a statement.
"High fuel prices are behind the fall in vehicle miles travelled," FHA transportation specialist Steven Jessberger told AFP.
"A number of public transportation authorities are reporting an increase in ridership compared with last year. The service I use has seen an 18-percent increase in ridership compared with a year ago," said Jessberger, who commutes 50 miles (80 kilometers) daily by bus into Washington.
In the first five months of this year, Americans put in nearly 30 billion fewer miles on public roads than in the same period in 2007, the data showed.
During that period, petrol prices rose from about 3.20 dollars a gallon (3.78 liters) to more than four.
Vehicle miles travelled in May this year were at their lowest level since 2003, FHA data showed.
In May 2003, petrol averaged around 1.70 dollars per gallon (3.78 liters) in the United States.
In May 2007, it had doubled to around 3.40 dollars per gallon, and a year later it was nudging four dollars per gallon, according to data from the Department of the Environment's Energy Information Administration.