Dems still pushing for hike in federal gas tax,why?

To date for calender year 2008,americans have driven 9 BILLION miles less than the same period for 2007.We are conserving and using less gasoline so the federal tax revenue is down.Go Figure!! Dems are pushing hard for an increase in the tax rate.So what do we do? Conserve and help save planet or conserve and be expected to pay more for congress to waste?