“Rolling coal” is now banned through a new law aimed to crack down on drivers who pump out plumes of black smoke.

In Fort Collins, it’s a regular problem.

“Some truck will rev up its engine and drive past me and blow smoke in my face,” said Genevieve Marmaduke, who regularly bikes around town.

RELATED: Bill could crack down on 'rolling coal'

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She’s been on the receiving end of someone rolling coal, and so have people eating on patios downtown. On occasion, police officers are targeted at night.

Fort Collins Police helped craft the new law that will fine drivers $100 if they are caught.

Tom Franklin, a diesel truck expert, told 9NEWS when a truck does blow out that much smoke, it’s a waste of fuel. He also said more people than not modify their trucks for a legitimate reason.

“For some, it gives them better fuel mileage and most do it for power,” he said.

It comes in handy for ranchers and farmers pulling tractors and heavy equipment. For that reason, Sen. Randy Baumgardner never supported the bill.

“I'm concerned those individuals might be possibly get a ticket for causing without trying to cause the rolling coal effect,” Baumgardner said.

It took two tries and overcoming opposition, but the bill is now officially law.

Other law enforcement agencies said they were waiting for the governor to sign the bill and learn more to figure out how to implement it.