Dust from the catalytic converter. I've heard of gangs in LA taking shopvacs to the shoulder of the freeway at night.

Doesn't pass sanity check. They would run street sweepers if anything.

And surface roads with stop and go would have a higher density of particles in the "go" places (like beyond lights).

But if the gangs can make money doing it why wouldn't the municipalities do it?

Pics or it didn’t happen. I’ll even accept AI slop if its well crafted.

Doing a public service, there.