For several days in May, New York City commuters were transfixed with the story of a subway saboteur who would sneak onto the back of trains and pull the brakes, wreaking havoc on the beleaguered transit system and their morning commutes.

The police eventually arrested and charged Isaiah Thompson, 23, in connection with the incidents, which delayed hundreds of trains. He was released on bond.

But only two months later, he was at it again, the police said.

On Friday, Mr. Thompson was arrested after he was seen riding on the outside of a subway car and was again charged with reckless endangerment and criminal trespassing. It was his 18th arrest — 17 of which involve the transit system.

“This man put lives at risk, endangering himself, our workers and his fellow passengers while disturbing the lives of thousands of people,” said Shams Tarek, a spokesman for the Metropolitan Transportation Authority. “We’re grateful to the N.Y.P.D. for their quick arrest and believe he should be prosecuted to the fullest extent of the law.”