More than 300 volunteers organized by Transportation Alternatives formed a six-block-long “human-protected bike lane” on Fifth Avenue last night, calling on the de Blasio administration to extend the protected bike lane network through Midtown’s busiest streets.

Fifth Avenue has no bike infrastructure above 26th Street, leaving a large void in the bicycle network where there’s huge travel demand. Protected bike lanes can’t come soon enough: Through the first eight months of this year drivers injured 15 people biking and 28 people walking on Fifth Avenue in Midtown, according to city data.

“Especially during high traffic hours, [Fifth Avenue] just feels a little scary because some of the drivers are driving aggressively,” said Jei Le, who started bike commuting to Midtown from the Upper West Side earlier this year.

Last month, DOT presented a plan to add a second bus lane on this part of Fifth Avenue, but a bikeway was not included. To date, the agency has hesitated to claim street space for biking and walking on these busy Midtown avenues. DOT has stated a vague intention to extend protected bike lanes through the busiest blocks of Fifth and Sixth Avenues but never backed that up with specific commitments, timetables, or designs.

The hundreds of people taking action yesterday were saying that’s not good enough and took matters into their own hands. The human-protected bike lane occupied two lanes, from 50th Street to 44th Street. Clarence Eckerson was there to document the action:

Fifth Avenue functioned perfectly well while the impromptu bike lane was in effect. People biking quickly gravitated to the new space set aside for them, while car and bus traffic continued apace in the remaining three lanes.

In a written response posted on DOT’s Twitter feed, Commissioner Polly Trottenberg framed the campaign for a bike lane as being in conflict with the second bus lane for Fifth Avenue. “We did not want to postpone what we see as a reasonably straightforward improvement for buses,” she wrote.

DOT is “working through the engineering questions required to design a safe and well-functioning bike lane on 5th Avenue,” she said, but gave only a vague timeline for when that work would wrap up.

But without public pressure on DOT to follow through, there’s no telling how long the public might have to wait for bikeways on the busiest Midtown avenues. It’s been four years since Community Board 5 called on the city to install protected bike lanes on Fifth and Sixth avenues. The city did respond to those requests — up to a point. The protected bike lanes on those streets extend only as far north as 24th Street and 34th Street, respectively.

In the past, DOT has redesigned streets for better transit and safer biking simultaneously. The overhaul of First Avenue and Second Avenue, for instance, included both bus lanes and protected bike lanes.

“There’s no excuse not to include safe infrastructure on all of our streets, especially big arterial streets that are already being redesigned,” TransAlt Executive Director Paul Steely White told the crowd last night.

Manhattan Borough President Gale Brewer, local Council Member Dan Garodnick, and City Council transportation chair Ydanis Rodriguez are all on the record in favor of a Fifth Avenue protected bike lane, and Rodriguez came out last night to show his support.

Community Board 5 will vote on the Fifth Avenue bus lane plan on Thursday. Advocates plan to press the case to DOT and CB 5 that the redesign of Fifth Avenue should also include a protected bike lane. The meeting starts at 6 p.m. at Xavier High School, located at 30 West 16th Street.