Maybe other areas of the country are seeing less traffic on the roads?
First, it DOES make a difference where you are driving. The entire country or even parts of states no doubt have differing amounts of traffic when compared to the past. It might also make a difference WHEN you typically drive. Some people are still driving but making fewer trips, combining errands etc but might still be found on the roads when YOU typically drive.
People are making fewer long distance/cross country type trips unless they are truckers and working. I also hear that some trucking companies have gone and are going to natural gas powered vehicles.
Second, a lot of people are driving vehicles that are much more fuel efficient than in the past.
I don’t know the specifics, but I hear on the news that America’s gasoline consumption continues to decline, per capita, year upon year upon year, which would generally fit the conclusion from the Energy Dept. data.