Loading "Tacking never completely stopped, it went quiet for a while, but now it seems to have ramped up again with a number of attacks in the last few weeks." VicRoads, which uses a magnetic mat to sweep and clear the boulevard of metal bits once a week, has collected an average of 240 tacks per month over the past six months. Since 2014, it has also spent $300,000 to address the issue. “VicRoads is monitoring the presence of tacks on Yarra Boulevard and our crews are regularly sent out to sweep the road," said VicRoads director of the metro south east region Aidan McGann.

“We are working closely with Victoria Police to ensure the safety of everyone using Yarra Boulevard.” Loading Police say some cyclists have sustained serious injuries as a result of the tacks which are so tiny they're almost impossible to see on the asphalt. One 86-year-old cyclist was thrown off his bike, broke his hip, and required surgery after he rode over a tack, Inspector Noy said. He described the offending as "mindless stupidty" that often targeted the community's most vulnerable.

People with disabilities and the elderly have also fallen victim with numerous reports of metal tacks puncturing the wheels of mobility scooters. Inspector Noy said police had also received reports of young children wearing thongs being pierced in the foot by the tacks, while animals, particularly dogs walking along the track with their owners, had tacks stuck in their paws. Other tacks have been found washed up in the river. Despite numerous pleas for public assistance over the years, the Boulie Tacker has never been charged.

Edward Hore, president of the Australian Cycle Alliance, believed the offender could be a copycat. Previously metal tacks were dropped near houses surrounding the track, but now, the attacks were targeting the start of the separation bike lane. The stretch of the track is popular among cyclists who are training. "The irony is that by targeting an area that takes bikes away from cars they're actually encouraging cyclists to avoid it and ride on the road instead," he said. "If their intent is to get cyclists off the road then it is an incredibly stupid way to go about it." Mr Hore said he'd been contacted by dozens of cyclists in recent weeks and called for greater security, including better lighting and the installation of CCTV.

Loading Inspector Noy said one of the biggest hurdles investigators faced was cyclists not reporting the incidents to police. "It's really hard for us to actually track the exact movements of the culprit other than trawling through cycling pages on social media where the incidents are reported because people don't always contact police," he said. "We are working with VicRoads ... so that we are able to actually track where these tacks are being dropped and to see if there is a pattern in offending." Inspector Noy said the culprit seemed to be targeting spots along the walking track at random.

Police also haven't ruled out the possibility there is more than one offender. "The key message we want to get through to people is that this doesn't just impact cyclists," he said. While the cost to cyclists could be huge, police had also invested enormous resources into the matter, "time that police could have spent investigating aggravated burglaries, assaults and sex offences," he said. He believed an 'anti-cyclist' mentality in some pockets of the area had also stalled the investigation.