Mayor Bill de Blasio wants to replace car lanes with bike lanes on the Brooklyn and Queensboro bridges.

Both bridges currently boast narrow paths that must be shared by both cyclists and pedestrians. The lack of space makes for harrowing and chaotic crowds, particularly on the Brooklyn Bridge promenade, which is popular among tourists.

Hizzoner’s plan — which he is set to announce in his State of the City address later Thursday — would replace the inner-most Manhattan-bound car lane with a two-way bike path.

The eight-foot-wide path would be separated from adjacent car traffic by a concrete barrier, according to renderings provided by the city.

On the Queensboro Bridge, Hizzoner wants to open up the span’s south outer roadway to pedestrians and make the existing bicycle-pedestrian path on the north outer roadway bicycle-only.

Construction on the Queensboro Bridge project is expected to wrap up in 2022.

The Brooklyn Bridge switcheroo, meanwhile, will be complete by the end of this year, officials said.

The landmark span was so popular before the COVID-19 pandemic, it often overflowed with people on busy weekend days.

But the bridge’s popularity has come with consequences — collisions are not uncommon, and bike commuters tend to avoid it altogether.

“It’s terrible. There’s just not enough room,” 53-year-old Brooklynite Scott Conti told The Post while making his way over the crossing by bike.

“Every time it’s crowded you almost run into something. Usually they’re tourists, people, little kids,” Conti said. “I have had a couple of experiences. I’ve been hit once.”

Cycling has boomed in New York City in the last year as many city residents avoid mass transit out of fear of contracting COVID-19.

“Even during the pandemic it seems there have been a lot of tourists standing in the bike lane taking photos,” Justin Sherwood, 31, said while jogging along the Brooklyn side of the bridge.

“I have seen a couple accidents where people got clipped.”