There was a time, long ago, when I first started running, that I wasn't too enthused about running in the dark. I need to clarify; "dark" is still under streetlights for the most part, never out of sight of city light, always on clearly visible pavement. So it's pre-dawn, from 4ish to 5ish in the morning, with gray, reluctant dawn at the end of the run for many months of the year.
I would see shadows, threatening shades of ursine and canine life, wandering humans of dubious intent. There was no out; if anything attacked, it would be just me, no comforting traffic or pedestrians to witness any aggression or attempted robbery. The old woman who would be on her way to or from the newspaper box, in a nightgown in the dead of winter, was an apparition that chilled my blood. For weeks I had trouble believing she was real.
My perspective has changed completely, even though the population of the pre-dawn world remains the same.
Now, I feel like I'm part of that world. The animals are not a threat in any way, since I'm aware of them and they're aware of me. We respect each other's space. The wandering people represent a need for greater caution, but some of them recur and I recognize them from a distance. It's a very fundamental, unadorned awareness that takes over, and I really like being in that zone. It's the perfect way to run, as approximate to the way our ancestors ran as I can get... albeit shod...
The staggering drunk who spewed an impressive fountain of puke at the side of the road this morning was a newbie, though. If he does keep up his routine, I'm sure that one of the cruising cops will help him to change his ways.
After years of seldom straying from the same route and the same daily time frame, I've grown into the time, the route, and the solitary peace of my training runs. Weekend runs usually happen a couple hours later, more like 7 or 8 am, so there can often be something closer to traffic, annoyingly bright sunlight and warmth, things that throw me off my routine.
I'm sure there are attractive aspects of running in the evening or the afternoon, but they don't affect me. I'm a pre-dawn runner, and likely always will be.