This is only the third time since 1970 that the year-over-year change in total U.S. miles driven has declined. The previous two times were following the oil shocks of 1973 and 1979 -- and led to the two most severe U.S. recessions since WWII.
But there is some good news: The Department of Transportation also reported that "greenhouse gas emissions fell by an estimated 9 million metric tons for the first quarter of 2008," presumably in part because of all the miles not traveled.
Right-wing think tanks are always complaining that taking meaningful action to address climate change will choke off economic growth. But it could just as easily work the other way around: A collapse in economic growth might choke off global warming.