Many countries (not the US of course) require auto-mobiles to have daytime running lights as it has been long ago proven to be effective in reducing accidents.
"Because the human eye is light-seeking, drivers will see an oncoming car sooner and make a more accurate estimate of its rate of approach. The effect is particularly important for peripheral vision, which may not see an object at all unless it contrasts sharply with its background or moves against it. Using daytime lights significantly reduces the chances of a car, cyclist or pedestrian moving unexpectedly into your path."
As such, my sense is that it would logically follow that a bicycle with a daytime running light would also reap a similar benefit.