The figure represents Moving 12-Month Total on All [U.S.] Highways until November 2008, but you can find all sorts of graphs telling the same story (including one I wanted to use showing how energy consumption has plunged in China over the past year, but which I can no longer find).
Energy consumption is down, miles driven are down...and this should be reflected in CO2 emissions numbers when such figures are released for 2008 and going forward.
PS. Where were gas prices in November? On their way down, I believe.