There is a big misconception about nuclear attacks. Full scale nuclear war with a adversary like Russia is indeed an apocalypse scenario, but a single lowish yield nuclear detonation by a nation like North Korea is very very survivable, if you are prepared.
I have a similar evac plan with a bug-out bag that I gave my wife to keep at her work. For nuclear attack specifically, she is instructed NOT to leave her work and hunker down in their concrete basement for two weeks. Even being much closer to an estimated ground-zero, she is far safer in their well-shielded basement than trying to get home in the open fallout zone. The bag has enough rations, batteries, water, first-aid, etc for that period. Fallout zone radiation levels take about 2 weeks to drop to safe levels, at which time she has a printed google map for her to walk the 20 miles home.
My job is to grab the kids at school and hunker down in our basement where we have more exhaustive supplies, and ultimately get the hell out of town together.
Fallout is the biggest killer. Using http://nuclearsecrecy.com/nukemap/, and unfortunately fallout is highly dependent on wind direction - an important unknown on that day.
Given the unknowns and the likelihood that roads will be quickly impassible, it is best to prepare at home. It takes two feet of concrete or packed dirt to block radiation to a safe level, and that includes ABOVE you. Wood provides almost no protection. ...but if you do have a basement, then you can make a plan to place very heavy items (appliances & server racks) on the first floor above you and vehicles and stones/dirt/etc around that part of the house.
Fallout settles on surfaces, so it's a good idea to trim bushes and trees directly around that shelter - you want the fallout to hit the ground, not settle at a higher angle above you. ...and if you're in Hawaii or other coastal area and have easy access to a boat, that might be the best option because fallout sinks and there are no traffic jams at sea.