Had a Truck roll coal on me and another rider today

[AngryScientist]

one thing to consider is that "rolling coal" MAY not always be an intentional act.

unless the truck is newer and tuned just right, generally speaking when you step on the go pedal quickly the air/fuel ratio goes rich and black smoke pours out.

I can picture a plausible scenario where a truck may slow down to give a cyclist some space and wait for oncoming traffic to make a wide berth in order to pass, and then, after slowing down creating black smoke while trying to accelerate quickly and safely pass the cyclist as oncoming traffic allows.

of course many times it is intentional, but maybe not every time.