Sue

I commute daily from Lakewood to Olympia, what many here don't realize is there really is not an alternative route except to have a plan to head out to the penninsula and take a ferry from Bremerton.
In the event of a catastrophic earthquake, I doubt many of the bridges and overpasses would survive. Counting the rivers between Everett and Centralia quickly adds up to over a dozen bridges, depending upon the time of year crossing some of them could be quite perilous.
Honestly, a good contingency plan problem should include networking friends and relatives along the way that could offer you a place to stay. In that kind of event you very well could be several weeks until you get home.
We are very vulnerable and I don't have to tell you that we are already too congested. Any disaster would make the situation quite untenable.
Do you know anyone with a boat? The only way you could be sure to get from one end of Puget Sound to the other after infrastructure failure would probably have to include water or airlift...