Warday by Whitley Strieber and James Kunetka.
I t is a fictional account of the authors travelling across the U.S. five years after a limited nuclear attack in order to assess how the nation has changed after the war.

Rule number 1:
Don't go and get the kids from school. You'll just die because you are in the open and so will they, if you picked them up and weren't home before the missile hit your city.

qjs