Observers of American life have long wondered what it would take to disrupt our love affair with cars. It turns out that $4-a-gallon gasoline might do the trick. Last year for the first time in 28 years, Americans drove fewer miles than the year before. Automakers can no longer sell their highly profitable but gas-guzzling SUVs. And across the country, mass transit systems have seen an increase in ridership, in some cases a dramatic one: ridership is up 11 percent in San Antonio, 17 percent in Baltimore and 28 percent in Seattle, according to the Associated Press. Summer driving plans are being altered. “Park and ride” lots for commuters are full.