I learned the hard way not to take shortcuts through parking lots, at least not in the dark. The cement blocks at the foot of parking spaces are not always visible, depending on how your lights are illuminating the path in front of you...

In fact, I think the fact that your vision is a bit more limited at night - to the area illuminated by your lights - is really the main challenge with winter commuting due to longer periods of darkness. Then again , I live in California and it never really gets too cold.