Rolling coal

Rolling coal is the practice of modifying a diesel engine to increase the amount of fuel entering the engine in order to emit large amounts of black or grey sooty exhaust fumes into the air. Such modifications may include the intentional removal of the particulate filter. Practitioners often additionally modify their vehicles by installing smoke switches and smoke stacks. Modifications to a vehicle to enable rolling coal may cost from US$200 to US$5,000.
Background.
Rolling coal is often done for entertainment purposes. Some drivers intentionally trigger coal rolling in the presence of hybrid vehicles (when it is nicknamed "Prius repellent"). Practitioners cite "American freedom" and a stand against "rampant environmentalism" as reasons for coal rolling.
A concern is road traffic safety violations, as the black smoke can impair visibility, increasing the risks of motor vehicle crashes, and is a violation of clean air laws.
Legality.
United States.
In July 2014, the United States Environmental Protection Agency stated that the practice was illegal, as it violated the Clean Air Act which prohibits the manufacturing, sale, and installation "of a part for a motor vehicle that bypasses, defeats, or renders inoperative any emission control device [and] prohibits anyone from tampering with an emission control device on a motor vehicle by removing it or making it inoperable prior to or after the sale or delivery to the buyer."
State Law.
California.
California law prohibits operating a vehicle "in a manner resulting in the escape of excessive smoke, flame, gas, oil, or fuel residue". The California Highway Patrol or local police can cite a vehicle under this section or others for rolling coal.
Colorado.
Prohibits nuisance exhibition of motor vehicle exhaust, which is the knowing release of soot, smoke, or other particulate emissions from a motor vehicle with a gross vehicle weight rating of 14,000 pounds or less into the air and onto roadways, other motor vehicles, bicyclists, or pedestrians, in a manner that obstructs or obscures another person's view of the roadway, other users of the roadway, or a traffic control device or otherwise creates a hazard to a driver, bicyclist, or pedestrian.
Connecticut.
No person shall operate a motor vehicle in a manner that causes a visual exhibition of smoke that consists of the release of soot, smoke or other particulate emissions to the air and onto roadways, other motor vehicles, bicyclists or pedestrians, with the intent to (A) cause a reasonable person to feel harassed, annoyed or alarmed, (B) obstruct or obscure any person's view of the roadway, other users of the roadway or a traffic control device, or (C) create a hazard to a motor vehicle operator, bicyclist or pedestrian.
Indiana.
Vehicles can have equipment to prevent "escape of excessive fumes or smoke". A Reddit thread referenced the potential for issuing a citation based on creating a safety hazard by obscuring roadway visibility.
Maryland.
A person may not knowingly or intentionally cause a diesel-powered motor vehicle to discharge clearly visible smoke, soot, or other exhaust emissions onto another person or motor vehicle. Exempts normal operations, large commercial vehicles, and construction site vehicles.
Massachusetts.
"No person operating a diesel-powered vehicle shall intentionally release significant quantities of soot, smoke, or other particulate emissions into the air, onto roadways or other vehicles in a manner that obstructs or obscures another person's view of the roadway, other users of the roadway, or a traffic control device or otherwise creates a hazard to a driver."
New Jersey.
Prohibitions relative to certain retrofitting of diesel-powered vehicles. No person shall retrofit any diesel-powered vehicle with any device, smoke stack, or other equipment which enhances the vehicle's capacity to emit soot, smoke, or other particulate emissions, or shall purposely release significant quantities of soot, smoke, or other particulate emissions into the air and onto roadways and other vehicles while operating the vehicle, colloquially referred to as "coal rolling ". New Jersey Department of Environmental Protection regulations also prohibit "smoking vehicles", and the department has a reporting hotline.
North Carolina.
In 2016, a question to the Western North Carolina Air Quality Director about "rolling coal" referenced state law. Vehicles driven on a highway must have equipment to prevent "annoying smoke and smoke screens". During any mode of operation, diesel-powered vehicles cannot emit for longer than five consecutive seconds visible contaminants darker than a specific density.
Texas.
The Texas Commission on Environmental Quality (TCEQ) decommissioned its state-wide smoking vehicle reporting program. Reports on smoking vehicles can still be made through the North Central Texas Regional Smoking Vehicle Program in the Dallas-Fort Worth area, which includes Collin, Dallas, Denton, Ellis, Erath, Hood, Hunt, Johnson, Kaufman, Navarro, Palo Pinto, Parker, Rockwall, Somervell, Tarrant, and Wise counties.
Utah.
Department of Motor Vehicles may suspend or revoke a vehicle's registration if notified by a local health department that the vehicle is unable to meet state or local air emissions standards. Except during warmup or heavy tow, or for vehicles with a gross vehicle weight greater than 26,000 pounds, a diesel engine may not emit visible contaminants during operation if manufactured after 2007, or may not emit contaminants greater than a specific density if manufactured before 2008. An incident of coal rolling on a cyclist was captured on camera in August 2018 and referred to the Kane County attorney. In March 2020 cast members of the Utah-based "Diesel Brothers" reality television series, and the companies they own, were fined a total of $850,000 for Clean Air Act violations.
County or municipal ordinances and reporting.
Hudson, Colorado.
It shall be unlawful for any person to engage in a nuisance exhibition of motor vehicle exhaust, which is the knowing release of soot, smoke, or other particulate emissions from a motor vehicle with a gross vehicle weight rating of fourteen thousand (14,000) pounds or less into the air and onto roadways, other motor vehicles, bicyclists, or pedestrians, in a manner that obstructs or obscures another person's view of the roadway, other users of the roadways, or a traffic control device or otherwise creates a hazard to a driver, bicyclist, or pedestrian. The ordinance, which was passed in September 2017, exempts several categories of vehicles, and provides for a fine up to $499.
Overland Park, Kansas.
The engine and power mechanism of every motor vehicle shall be so equipped and adjusted as to prevent the escape of excessive fumes or smoke.
Salt Lake, Davis, Utah, Weber/Morgan Counties, Utah.
These counties have "smoking vehicle" report forms online.
Cheyenne, Wyoming.
A person shall not engage in a nuisance exhibition of motor vehicle exhaust, which is the knowing release of soot, smoke, or other particulate emissions from a motor vehicle with a gross vehicle weight rating of fourteen thousand (14,000) pounds or less into the air and onto roadways, other motor vehicles, bicyclists, or pedestrians, in a manner that obstructs or obscures another person's view of the roadway, other users of the roadway, or a traffic control device, or otherwise creates a hazard to a driver, bicyclist, or pedestrian. The ordinance, which was passed in July 2017, exempts several categories of vehicles and provides for a fine of up to $750 and up to six months in jail. A first attempt in July 2016 failed, but Cheyenne police had clarified at that time that they had been writing tickets for coal rolling under state law.
Provincial Law.
British Columbia.
"A person who contravenes this section commits an offence and is liable on conviction to a fine of not less than $50 and not more than $5,000."
Ontario.
The Ministry of the Environment, Conservation and Parks prohibits tampering with the emissions systems of diesel vehicles in order to produce "visible emissions". Fines range from $305 to $1,000 CAD.