(Courtesy Flickr #dieseltruckaddicts)

Coal rolling is when people driving cars and trucks intentionally belch black clouds of exhaust on pedestrians, cyclists, Prius drivers, al fresco diners and liberal protestors. Lawmakers in both parties decided it has become a road, health, and safety hazard in recent years, and they passed a bill penalizing coal rollers. Governor John Hickenlooper signed it into law on June 5.

SB17-278, sponsored by Rep. Joann Ginal, a Democrat from Fort Collins, and Sen. Don Coram, Republican of Montrose, makes coal rolling a traffic infraction and sets a fine of $100. It passed with wide bipartisan support after failing on two earlier attempts after being modified to appease truckers and farmers. The final bill does not take points from drivers' licenses for coal rolling, and it exempts farm vehicles.

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Tampering with car exhaust systems is illegal under the federal Clean Air Act. Yet the phenomenon of coal rolling has spawned competitions where the most smoke wins, a reality show, and a glut of YouTube videos that proudly depict coal rollers enveloping people or other vehicles in sooty smoke -- sometimes as a political statement.

Colorado Matters host Andrea Dukakis talks to Rep. Ginal about her personal encounters with coal rolling in Fort Collins, and the challenges of cracking down on the phenomenon.