Years ago (for my dark work commutes in all weathers) I added a little 2-beam LED sequencing bike light to my rear crash bar, above my tail light.
(it can be set to flash various ways)
Turned it on today before the ride home as a heavy fog had rolled in.
Not bad in town....
But very thick on the ride home.
(thick enough that I daren't stop on the road for a pic - pulled into the bike trail)
I was dripping from helmet to boots when I reached home. Rain pants and hi-viz rain over-jacket* kept me dry.
(*the Brits know how to deal with the rain!)
Stig