The days are short and the nights are long. (Global darkening?) As I was bicycling in to work this morning - in almost-dark - I caught an occasional glimpse up ahead of a red light. I assumed it was a taillight on another bicycle. And I was right.
As I got closer, I saw that the rider, dressed in dark attire, had a light on the back of his fat-tire bike, attached to the seat post. (A very common thing; my taillight is attached to the seat post.) But the other rider also had a rack on the back of his bike - and a bag attached to the rack, right behind the light. The taillight was impossible to see from directly behind. A driver might see it just as he's plowing into the guy.
I've got my little Chinese single-AA LED flashlight, for my headlight. When it has a fresh battery, it's amazingly bright... I can see signs reflecting back at me a half-mile up the road. But it uses the juice to produce that bright light, and as the battery power diminishes, the light grows weaker and weaker, until I can't even see it on the road just in front of me. Ultimately it quits blinking, and just glows a steady night-light glow... at that point it's essentially useless for being seen or seeing. (I carry a spare battery, so I won't get into a hazardous situation.)
Another common sight, this time of year... people wearing a thick knit cap... with a helmet perched on top. They're obviously safety-minded, but in the event of an accident, unless the head-impact was directly on top of their head, the bucket would almost certainly just get knocked sideways, rather than providing any impact absorption.
It's a little sobering, but true... our lives can literally depend on that gear. If you're sharing pavement with 4000-pound hurtling missiles, sometimes with distracted or impaired pilots, it is absolutely imperative that you take measures to be as visible as possible! For me, that means functional lights that can be seen 360 degrees around the bike, and light clothing. Some people are obviously comfortable riding alongside the road on their black bike in dark clothing, without any lights and muddy reflectors. I see 'em regularly.