SAN FRANCISCO (KGO) -- A new government study shows commuters in the Bay Area are ditching their cars more so than any other major U.S. city.According to the Census Bureau report , 70 percent of commuters in San Francisco, Oakland and Hayward use their car to commute, which is down almost 4 percent from 2006.That's the biggest drop in the country.Boston saw the second biggest drop in commuters who drive, followed by Durham-Chapel Hill, North Carolina.