Gary,  a far worse situation would have occurred if vehicles on side streets were not held at bay.  Those on side streets would have been stuck all morning instead of less than hour.  Drivers on side street would have been stuck all morning instead of less than hour simply because none of them could have gone thru an intersection that became a parking lot.  Mind you we're talking here of a system that manipulates 400,000 vehicles a day to the same system manipulating vehicles on Nimitz or Dilingham.  It appears that Artificial Intelligence software could be driving the computers because of its ability to "clear a path for escape".  AI in a disk is well known in the game of chess as being far superior in intelligence to many of the most intelligent chess player.