This is was the highway I would use to drive to San Francisco, via the Bay Bridge. 

A truck crashed and exploded underneath, with flames shooting up 200 feet high, causing the upper deck of  highway 580 on the Oakland/Emeryville side leading to the Bay Bridge to collapse.

Gov. Schwarzenegger is expected to announce an incentive - most likely free rides - to use public trasnportation.  Expect a nightmare on BART.

(more at the Chronicle)

Update: another pic from Thomas Hawk, via Scoble. 

Another photo below: