side visibility (or lack thereof) is one of the things that tends to separate "see lights" from "be seen lights". most high-output "see lights", even bicycle specific ones, do little or nothing to increase conspicuity from the sides. all decent "be seen lights" throw some light to the sides.

if you're on the road, you should always have a "be seen light" up front. add a "see light" as needed.

my biggest problem with using a high-output flashlight as a "see light" is that it doesn't have a battery indicator... but i can solve that problem by carrying a spare 18650.