The mother of a 15-year-old Manhattan boy killed “subway surfing” on the Williamsburg Bridge plans to sue the MTA for failing to block off empty parts of the train used for the daredevil stunt, she told The Post.

Norma Nazario of Alphabet City said she reviewed footage on her late son Zackery’s phone and that it showed nothing prevented him from climbing onto the roof of the J train, where he eventually hit his head and died Monday.

“[The videos] show he has easy access. No alarms, no security, no cameras, no anything!” Nazario said ahead of her son’s wake Thursday evening.  

“He was able to access anything in the trains, the empty cabins, the train stations, nobody [was]  looking. I was so surprised.”

The grieving mother said transportation honchos have known for a decade that thrill-seeking teens ride on the outside of trains — but have made no apparent effort to restrict access to those areas.

“Don’t get me wrong, my son, he had no business doing what he did. But they knew 10 years ago kids did this so easily,” she said. “My son died. When are they going to do something?”

She added, “Obviously I am planning to sue.”

Nazario said she wants to discuss possible subway-surfing safety-prevention steps with Mayor Eric Adams but didn’t elaborate.

Zackery was riding on the roof of a northbound J train across the bridge with his girlfriend when he slammed his head on a metal beam at 6:45 p.m and fell beneath the train, according to police.

He had apparently turned his head back to look at his girlfriend when he was struck and fell.

Nazario cremated Zackery’s remains Friday and said she planned to move his ashes to her family’s apartment.

“I’m going to bring his ashes home. I want my son in his room one way or another,” she said.

Subway surfing incidents increased 560% between January and May last year, MTA data shows — with 449 incidents compared to just 68 during the same period in 2021.