+1 on the practice changing tires/tube.
Five miles is not that long a commute, and unless it's a catastrophic tire failure you could probably make it to your destination by pumping it every so often, or at least make it out of the darkened treacherous highway area.
I haven't had to repair a flat on the side of the road yet, but I have had two flats in the past two weeks after arriving at my destination. I know it's inevitable that at some point I'll have to repair on the side of the road, so I choose my route very carefully to avoid just such an area as you described.