After noon， in Manhattan. It's slightly overcast， not cold， a good day for walking. I'm in the 90s on Fifth heading south，enjoying the broad avenue， the trees， the wide cobblestonewalkway that rings Central Park. Suddenly I realize: Something'sodd here. Something's strange. It's quiet. I can hear each car go by.The traffic's not an indistinct roar4. The sidewalks aren't full， as they normally are. It's like a holiday， but it's not， it's the middle of a business day in May. I thought back to two weeks before when a friend and I zoomed down Park Avenue at evening rush hour in what should have been bumper-to-bumper traffic.