In a country where cyclists are expected to have a working bell on their bikes, it was probably only a matter of time before fixies fell afoul of the law in Germany.

Evolved from indoor track bikes with no gears and brakes, fixies have long been favoured by couriers and other cycling enthusiasts in big cities around the world. But a surge in popularity in Germany has prompted an unprecedented backlash by traffic cops in Berlin in recent months.

“Interest in fixies has exploded in the past two years,” said Dustin Nordhus, owner of the Cicli Berlinetta bike shop in central Berlin. “Everyone sitting in an office all day thinks they’re cool these days.”

Nordhus has filled his shop with gorgeous high-end racing bikes that are street legal, but he also makes custom track bikes for a growing market of fixie riders.

Since there’s no freewheel on a fixie, the pedals continue to rotate as long as the bike is moving forward. This means the rider either has to slow the bike by fighting the momentum or brake by locking up the back wheel to skid to a stop.

Seeing what they considered a growing danger to traffic safety, Berlin police announced this spring they would begin cracking down on fixie riders. Since only April, they’ve confiscated 18 bicycles.

“Fixies have become a real problem,” Rainer Paetsch, a Berlin police official for traffic issues, told The Local. “It wasn’t a hunt, but we decided to do something to undercut this trend.”

To get their bikes back, cyclists have to pay a fine and convince the authorities they won’t ride them on the street anymore – or at least show an inclination to install brakes on them.

“For all I care they can ride them in their backyards,” Paetsch joked. “We just want people to realise it’s too risky to ride them around the city. Then we’ll be content that we’ve helped improve traffic safety.”