Americans drove more miles in 2015 than any year since the U.S. government started keeping records 45 years ago. The U.S. Department of Transportation recently reported that Americans drove a record 3.148 trillion miles last year. In case you are wondering, that is enough to take 337 round trips from Earth to Pluto. There are number of reasons Americans are driving more, according to experts. The first is the price of gas, which has dropped to 2004 levels in the past year. The American Automobile Association said the average price of unleaded regular gasoline is $1.71 a gallon, or 45.17 cents per liter. That is the lowest price since 2004. P.J. Sriraj, interim executive director of the Urban Transportation Center at the University of Chicago, said the lower cost to fill up a car or truck is just one reason Americans are driving more. Another reason is that more Americans are back to work after the 2008 recession, and driving to their jobs, he said.