At this time of year, both of my commutes are in the dark. You need a good lights on the front and rear. That is a given. My front weapon of choice is a bar-mounted direct-from-China CREE unit that cost arount $40. It can cast shadows a block away.

But you also need a headlamp. Trust me on this; my experience comes as a result of uncountable bike/car interactions in the dark, in which my bacon was saved many times by having a powerful lamp that I could focus right between their eyes.

Your biggest risk is vehicles that come from the side, and only make cursory rolling checks as they cruise through stop signs on residential streets. I have seen this hundreds of times.

It is only when they think that a freight train is bearing down on them will these drivers actually freakin' stop - like the sign at the intersection plainly states. A LED flashlight attached to the helmet is good. A powerful lamp that can be focused is even better. I have a 900 lumen CREE-based lamp, in which the total output of the beam can be focused down to about a foot square a block away. Having this pouring into your retinas is a awe-inspiring experience. Because it is so high and so powerful, I have had drivers pull right off of the road because they think I am a semi with one light out.