American motorists wasted more than $2.1 billion in the past year by spending extra for premium gasoline in vehicles designed to run on regular fuel, according to an AAA study released Tuesday.

Another way to look at that is that congested roads cost Americans over $100 billion a year (calculated both as wasted fuel and time). It’s not much better in the skies, where Treasury ...

The study by the Texas Transportation Institute examined 328 of the most congested stretches of highway in the nation and ranked roadways based on the amount of fuel wasted due to congestion.