Aaaannnndddd it looks like I have to drive for the rest of the week. Sprained my foot. Considering I sprained my foot well before I posted that 17.6 MPH average speed earlier I don't see it hurting my riding, but you know how Doctor's orders are...
Kind of a shame really, that commute was suburban and was a number similar to my overall averages when I would start from my urban apartment and ride towards the country for workouts a few months ago on my "fast" bike.