People did not start arriving on the overpasses in large numbers until Wednesday. Some of the people seen on the highway overpass near the Superdome had been inside the dome during the storm.
People congregate at the end of a sunken highway in New Orleans August 31. Note the presence of rescue vehicles in this Wednesday photo.
Bump
I believe those are prisoners being evacuated to the roadway.
Re photo in #62 where rescue vehicles are with the people on a highway on the 31st ---- note the accumulation of trash
which had to have been wrapped around food of some sort. The Times-Picayune was not printing complimentary papers!