I commute to work at 4 AM. Not much traffic, but that in itself is a problem because the few cars that pass may be paying less attention than usual (scary when you think how distracted drivers are usually).

I use two rechargeable blinkers in the rear, one on the helmet and one on the bikes rack, an 1100 lumen headlight (bright!), and tires that are called "Reflex" by Schwalbe meaning that they have a reflective ring around them. These reflective rings around the tires work... I took a flash picture of the bike at night once, and the rings around the tires washed out most of the picture!