From the back of the book:

You are Cal Phoenix, the freeway warrior, champion and protector of Dallas Colony One. You are leading your people on a life-or-death journey to the California coast. Now your exodus has reached the third stage - taking you through the deadly wastelands of New Mexico and Arizona, where lethal radioactivity threatens you at every step. Can you find your way... or will you perish in the poisonous omega zone?