Maryland has banned the practice of “rolling coal” in which drivers of diesel pickup trucks intentionally spew black exhaust at pedestrians, cyclists and other motorists.

Yes, it’s a thing. The Internet abounds with videos.

As of Oct. 1, motorists who intentionally blow visible exhaust at a person or vehicle can be fined up to $500. Rolling coal is done to attack protesters, show disdain for “foreign” or hybrid vehicles, or, apparently, as a dirty prank, according to the videos. Maryland Gov. Larry Hogan (R) signed the bill Thursday.

Rolling coal requires a driver to have overridden or tampered with a vehicle’s emission controls, said Allen Schaeffer, executive director of the Diesel Technology Forum, which represents diesel engine manufacturers and suppliers. Schaeffer said his group supported the legislation, along with Bike Maryland, because it’s unsafe and bad for the environment.

It also gives diesel engines a bad name, he said.

“Nobody wants to see a black puff of smoke coming out of any vehicle,” Schaeffer said. “It’s a very small fraction of a universe of people who do this, but it’s not representative of the current world of diesel technology that people have worked so hard to make clean.”

Kim Lamphier, of Bike Maryland, said her organization has heard a growing number of complaints in the past four years, particularly from cyclists and runners on rural roads, where some motorists apparently want to give them the message of “you don’t belong.”

“It’s horrible because you can breathe this stuff deep into your lungs and be coughing for several days,” Lamphier said. “For people with asthma who cycle, it can be a lethally dangerous combination.”

Schaeffer said it’s primarily a problem with diesel pickup trucks, not tractor-trailers. New Jersey and Colorado recently passed similar laws, he said. Tampering with a vehicle emissions-control system is also illegal under federal law.

Maryland Del. Clarence K. Lam (D-Howard) said he sponsored the legislation because the practice has “gotten out of hand” on Maryland roads.

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

The ban does not apply to diesel vehicles that discharge visible exhaust during normal acceleration, commercial vehicles weighing 10,000 pounds or more, or vehicles on construction sites.