Oil deposits and other shit on the road surface.it’s not only the salt on the roads in this city it rains idk what. There is forever a film of suit slurry on my truck that needs sprayed off regularly.
When it first starts to drizzle, that stuff is liquified and SLICK.
I had a motorcycle wreck in SW Michigan about 1976 due to that stuff, immediately after it started softly raining, and I (as a young motorcycle rider) misjudged how long it would take a woman with too many children in her station wagon to maneuver a simple right-hand turn off the main roadway into a parking lot.
OUCH!! Still have scar tissue on the inside of my right ankle!