A group of anti-environmentalists and truck enthusiasts have been modifying their diesel truck engines with smoke stack kits so their vehicles release thick clouds of black soot onto bystanders or Prius drivers.
This practice, which has been nicknamed "rolling coal," has congealed into an Internet subculture covered by Vocativ in a recent article. Practitioners post photos of their modified Ram trucks and Chevrolet Silverados with smoke stacks at times referred to as "Prius Repellent."
The modifications to the trucks including several components that increase the amount of fuel entering the truck's engine. Fuel that fails to combust properly, according to DieselHub.com.
Numerous coal rolling videos have cropped up on YouTube, including this one: