One of Mayor Bill de Blasio's trademark initiatives is in danger of becoming little more than a feel-good slogan, according to bicycle advocates. 

Almost two thousand bikers, many wearing orange vests and yellow shirts, took over Fifth Avenue on Thursday evening, rallying for the administration to dedicate more funding to its Vision Zero initiative while improving how the Police Department enforces it. 

"[Vision Zero] in danger of becoming just a mere slogan," said Paul Steely White, executive director of Transportation Alternatives, the nonprofit that organized the rally. "We're here to demand the mayor recommit to Vision Zero. And first and foremost that means real investment in street redesigns."

The Department of Transportation outlined more than 400 dangerous corridors and intersections last year. Bikers demanded additional capital funding to "fast-track" the installation of protected bike lane and "safeguarded pedestrian crossings" at those locations. 

Cyclists stretching several blocks rode down the avenue, from Grand Army Plaza at the foot of Central Park to Washington Square Park, in support. They called attention to the 17 cycling deaths this year, which has already surpassed the total number of deaths from last year, 15, according to city records. 

During the first two years of Vision Zero, launched shortly after the mayor took office, traffic fatalities dropped by 22 percent. Last year was the safest for city streets since record keeping began more than a century ago, in 1910, according to the city. 

Despite the improvements, ralliers cautioned that the decrease wasn't happening fast enough to reach Vision Zero's ambitious goal of zero deaths by 2024. The street death count this year is on pace to plateau, casting further doubt among advocates.

"The mayor committed to a number. I was so hopeful with the new administration and I've been sorely disappointed," said Ellen Foote, of Gowanus, whose son, Sam Hindy, died while biking on the Manhattan Bridge in 2007. "It's been lots of public relations. No statements -- we need leadership. We need the mayor out here." 

In a statement, Austin Finan, a spokesman for the mayor, pointed out that the city is installing 18 protected bike lane miles -- another city record -- and has pledged to install at least 10 protected lane miles moving forward, double the city's pace in the administration prior. 

"No cyclist death is acceptable," Finan said. "That's why we're continuing to step up our enforcement against dangerous driving and adding record numbers of bike lane miles to our network this year, 18 of which are fully protected."

Some of the Council's most vocal members on street safety joined cyclists for the ride, including Carlos Menchaca, Jimmy Van Bramer, Antonio Reynoso and Helen Rosenthal. 

"In this Vision Zero moment we should be celebrating zero deaths," Van Bramer said. "But when more cyclists are dying, there's an obligation to ride, stand up and demand changes."