I drive from Centralia, WA to Seattle (85 mi) or down to Portland, OR (95 mi) regularly, and as driving entertainment, I think about what I would do if a large earthquake hit.
That's funny.  I work downtown Seattle, and that is my primary planning scenario.  :-)
If I were in Seattle when the same quake hit, I'm afraid that I would be SOL for seeing home soon. It would probably take me at least ten days to get there, or even more if I had to do much backtracking. And youbetcha, it would have to be on foot. Downed overpasses, abandoned vehicles, tons of fallen debris... yuck!
Indeed.  The windstorm of 2006 gave a good preview of how transportation really gets honked up when you throw in a little debris.  I had to traverse the east side that day and while it is a bit less urban there, it was still a mess.  The 520 bridge was closed, but I had no way to know.  News was... well, less than helpful.  I ended up traversing a bunch of places I wasn't familiar with.  The GPS was very helpful.  And the kicker is..  just a *little* bit worse and it would have gotten real interesting...  As it stood, I could still *drive* (with some backtracking and routing around).  
 
 [out and about in Bellevue]