Mike Hanna, identified as the driver of a black pickup truck ‘rolls coal’ on Black Lives Matter protesters in Maryland last September. (Photo: ScreenCap)

Maryland has become one of the latest states to ban “rolling coal,” in a growing national crackdown on diesel vehicle drivers who intentionally tamper with engines to produce excessive amounts of black exhaust at the flip of a switch.

The practice has been widely popularized by right-wing and conservative Web sites.

The sites feature videos applauding pickup truck drivers and others who roll coal while driving past protesters, cyclists and, oddly, Toyota Prius drivers.

Maryland Republican Gov. Larry Hogan Jr signed the bill into law today (May 25) banning “the intentional discharge of diesel vehicle exhaust at cyclists, pedestrians, and other vehicles.”

Vehicle owners must tamper with diesel vehicle emission controls to create the thick exhaust.

The practice is “wasteful, harmful to the environment, and poses a safety risk for cyclists and others,” according to the Diesel Technology Forum, Bike Maryland and other groups backing the legislation.

The bill (HB 11), sponsored by Maryland Del. Clarence Lam, specifically targets rolling coal. State and federal laws already outlaw tampering with emission controls.

“Over the last year, I have heard from an increasing number of cyclists, runners, and drivers who have been coal rolled throughout the state,” said Lam in a statement.

“The passage of this bill into law is a recognition that the practice has not only gotten out of hand, but is both posing a real danger to the health and safety of others and hurting the environment,” he added.

Last year, New Jersey became the first state to specifically ban rolling coal. The law imposes fines of up to $5,000, about the cost to modify an engine to belch smoke.

Colorado and California have also enacted bans.

Coal rolling diesel drivers say they modify their vehicles for fun and as a form of protest, according to The New York Times.

But cycling groups don’t see it that way and neither do diesel truck makers.

“Bicyclists are particularly vulnerable when excessive diesel exhaust is intentionally blown at us for no reason than to do harm,” said Kim Lamphier, Advocacy Director of Bike Maryland.

“For the last decade, diesel engine and truck makers have invested billions of dollars to produce engines that are now near-zero in emissions,” said Allen Schaeffer, Executive Director of the Diesel Technology Forum.

“Tampering with engines and emissions controls for the purpose of generating excess emissions on demand is offensive, unsafe and harmful to the environment, and it is not representative of the manner in which diesel engines were designed to operate,” he said.