This is very real to me as my wife works 15 miles from Chicago and commutes about 20 miles farther out.
I can't work out this scenario as in the suburbs, there is only one choice of transportation- car. She can't get within 4 miles of our house from any form of public transportation.
That being said, she works with 90 people, many coming in the same general direction, so grouping up would be the next best alternative. If driving was out, and things were turning SHTF, hunkering down at work would be possible as they do have a cafeteria.
I take this exercize seriously as I was in the 89 SF quake, quite unaffected in the East Bay, while neighbors who had business on the peninsula couldn't communicate home for 6-10 hours, and some didn't get home until the following day.
I guess our current situation in Chicago looks a lot easier to figure out, but I am still stuck on "I don't know" regarding the original premise.