Why shut down public transportation?

I'm not getting the authorities' reaction on Oahu during the tsunami non-event Saturday, nor on the East Coast anticipating Sandy.

If your goal is to move Americans to public transportation, then it seems to me you keep public transit going as long as possible, you don't shut it down at the first opportunity.

At some point, you've got to stop, but later rather than sooner.

It's already tough to have to rely on a bus system which, in most places, doesn't run 24 hours a day; compared with private cars which are good to go anytime. It just makes it tougher when the mayor shuts it down on a whim.

What did that accomplish on Oahu, other than to frustrate people?