For the past century, the greatest ticket to freedom for every teenager in the suburbs was a driver’s license. After a lifetime of being chained to your parents—chauffeured around from school to practice to the homes of friends—there is no feeling more adult than the first time you take a car out alone. The next stage of your life has finally arrived, and you are barreling through it at 75 miles per hour.Car culture was pervasive in the United States for years: The annual number of miles traveled by auto rose decade after decade. Until 2004, that is, when it stopped short.