I do not believe that any major city in the USA can be evacuated in a few hours time. The same comment applies to almost all of the major cities around the world. Cities have grown so big, that they are far beyond the capability of their transportation systems. Most large cities are struggling to handle the tide of commuters at rush hour. THAT is their max capacity for moving people. It is literally impossible to evavuate most of the people in a short period of time.

The world has gown to the point where our large cities are "sitting ducks". If any critical emergency happens that threatens the lives of many people, a negative outcome may be unavoidable.

Sad but true.