I've found three things that have made a noticeable difference.

#1 . Construction vest or other hi-viz clothing. I've found the neon green/yellow color to be better than orange, but both are better than nothing.
#2 . An upright position. My only close calls have been when I'm tucked down coming down a hill.
#3 . Riding more towards the center of the lane when approaching cross streets. I've had people start pulling out on me when I'm on the far right, so if I see them waiting to come in, I move left (assuming no cars to my left of course).


Lights make a difference in low visibility conditions (fog, rain, etc.) but I didn't notice any difference in the daytime so I stopped running them.