A crucial portion of the Hudson River Greenway uptown will close for four months for repairs starting next week, according to Parks Department officials, and cyclists remain furious that the project does not include a safe detour and, instead, sends them onto crash-prone neighborhood streets.

The city contractor will close off a roughly 1.4-mile portion of the bike and pedestrian path between just north of the W. 181st Street pedestrian bridge and Dyckman Street starting Monday, Nov. 7, in order to allow repairs the Henry Hudson Parkway’s retaining wall and the greenway’s sinkhole-laden pavement, Parks spokesperson Crystal Howard told Streetsblog.

Officials drew up a detour via W. 181st Street, Broadway, and Dyckman Street to close the gap, but rejected a proposal to repurpose an underused lane on the adjacent highway for a protected bike lane.

Commuters can also pedal across town to the Harlem River greenway to connect to bike lanes at W. 155th Street, according to Hudson.

Inwood cyclist Allegra LeGrande, who usually rides the greenway daily to school and work downtown with her kids, said the city is cutting off a crucial connection.

“It’s the only way to get to school without risking death,” LeGrande said.

City crash data from the detour show that 100 collisions have injured 36 along the corridor this year through Oct. 28, or roughly 10 crashes per month. Those crashes have injured eight cyclists, six pedestrians and 22 motorists.

The Department of Transportation will set up signs at 27 intersections asking drivers to “share the road,” but the nearly two-mile, hilly bypass lacks serious bike infrastructure.

Broadway makes up the majority of the alternative route and the two-way thoroughfare serves as a major trucking and freight route without having any bike lanes. On W. 181st there’s only a shared lane with “sharrows” and the detour stretch of Dyckman has only a painted bike lane.

“There’s no way I would let my 11-year-old ride up and down Broadway,” LeGrande said, adding she will avoid traveling south during the repairs. “Why would I go downtown if New York City wants to kill me to get there?”

One Washington Heights resident said the steep hill on W. 181st and the long incline on Broadway will also deter many riders.

“That’s an impossible climb, unless you’re a real sportsperson,” said Melanie Yolles of W. 181st Street. “I mean it’s crazy to send anybody up that hill, especially if you’re carrying children.

“They really should have blocked off a lane of the highway and not send people into the mountains there,” Yolles added.

The agency shot down the idea pushed by locals and a well-known traffic expert to take a vehicle lane of the Henry Hudson Parkway for a protected bike lane during construction, claiming in August that would cost $2 million and that the state DOT in charge of the highway would have to conduct an eight-month traffic study.

Parks did not provide details of how it arrived at that price estimate and the state’s Transportation Department did not respond to a request for comment.

Community Board 12 recommended installing a bike lane on the highway using jersey barriers a year ago, and the city’s former Traffic Commissioner “Gridlock Sam” Schwartz endorsed such a move for the renovation project.

LeGrande said Parks, which has a history of poorly managing other greenways like Brooklyn’s Ocean Parkway, wasn’t interested in providing a safe travel alternative, because they’re focused on recreation, not transportation infrastructure — just as the city should be getting more New Yorkers out of cars and into environmentally-sustainable modes of travel.

“The Parks Department has absolved itself of any responsibility to provide continuity of service,” she said. “It demonstrates that the Parks Department needs to have authority over the greenway be taken away.”