When you get down to it, you try to avoid two things when running in the dark: Falling down and getting hit by a car. (Yes, you try to avoid these things running in sunlight, too, but darkness magnifies the difficulty of the tasks.)
Earlier this winter, I offered a cautionary tale about what can happen on even your most familiar running routes. I let my guard down for a second, and I fell down.
Getting hit by a car also happens when you, or the driver of the car, let your guard down for a second. Obviously, you should pay attention at every intersection and street crossing, erring on the side of caution. Most people are lousy drivers, after all.
Now, you can't control how other people will drive, but you can control how you appear to them. One way to make sure drivers see you is to dress like this:
I hit most of the colors of the rainbow here: Red shoes, blue hat, green shirt, yellow vest, black tights and pasty white skin. And this doesn't even include my headlamp, which I put on after snapping this pic when I realized how dark it was outside.
Do I have any evidence that, had I dressed otherwise, a car would have hit me? No. But I imagine I was pretty hard to miss.