Larry Willis’s colleagues liked to joke that he kept a copy of the Railway Labor Act, passed a few years before the Great Depression, under his pillow.

“He loved the wonk,” said his wife, Amy York. “He could explain things in a way that normal people could understand.”

Willis spent decades immersed in the arcane details of transportation law, pressing for workers’ rights during moments of national crisis, from the aftermath of the Sept. 11, 2001, terrorist attacks to the coronavirus pandemic, and the quiet times in between.

He sought progress as a congressional staffer and eventually as president of a labor federation representing 33 unions and millions of workers, the Transportation Trades Department, AFL-CIO, bringing what colleagues said was an intense curiosity and decency to a mission rooted in his sense of justice and Jewish faith.

That drive also defined his personal pursuits, including his passion for biking, his family and friends said. On Monday, those who loved him were struggling to process a heartbreaking loss.

Willis was critically injured Nov. 21 in what U.S. Park Police said was “a crash involving a motor vehicle and a bicycle” near the MacArthur Boulevard entrance to Great Falls Park in Maryland. Willis’s family said it appeared to be a terrible accident at a blind spot. Willis, who lived in Chevy Chase, Md., died Sunday. He was 53.

“He liked to be in constant motion,” York said. “He was doing something he really loved when he died. He really did love biking.”

Willis and York met at a parade in Iowa when he was 21 and she was 20. He was charming, and “his first words to me were, ‘Would you like a Dave Nagle for Congress sticker?’ ” — even though she had worked for the Iowa Democratic representative’s campaign the previous year. Their first date was five days later.

Now their daughter, Samantha, 19, is about to declare a major in architecture. Willis had so wanted Samantha to try out for the swim team, at not quite 6 years old, that he promised her anything in the world. She collapsed in his arms after practice, sobbing in exhaustion, and went big on her wish, telling him: “I want to swim with dolphins.”

Willis, who saved money for experiences and not things, made it happen.

“There was just this energy about him, kind of an underlying energy. It was always there. He was so excited with you whenever you got good news, but also sad with you when you didn’t,” said York, who is executive director of the Eldercare Workforce Alliance.

Those with whom Willis worked and mentored in the labor movement said his swift disappearance from their lives was difficult to fathom.

“For somebody who was living so big and so passionately to go so quickly and unexpectedly has been really hard,” said Elizabeth Baker, a colleague Willis recruited from Capitol Hill and eventually encouraged to take a job as director of government affairs at the Air Line Pilots Association.

Willis’s predecessor at the Transportation Trades Department — which represents everyone from transit workers and flight attendants to sheet metal and electrical workers — said Willis brought a fierce energy and deep understanding of policy minutiae to his advocacy work. Edward Wytkind said Willis built relationships across the aisle, among union leaders and with presidential administrations, and knew when to be unyielding and when to compromise.

Willis was a “workhorse, who took on so many of the really tough, tedious, often arcane laws” that were at the heart of protecting transportation workers and treating them fairly, Wytkind said. After 9/11, Willis fought for years to make sure new security laws didn’t unfairly sideline good workers with minor blemishes in their past, Wytkind said.

Willis’s command of detail made him an effective communicator and watchdog, Wytkind said, and he was good at “humanizing the importance of transportation by making it part of all the conversations on how you recover and grow the economy.”

He said hundreds of thousands of transportation workers remain on the job today in part because of the advocacy of Willis and his colleagues related to pandemic aid legislation passed by Congress. “This work leading up to his tragic death has been incredible,” Wytkind said.

He did that work with a joyful touch and humanity that left a deep impression, friends and colleagues said.

“He was really without ego in a place, a city that has so many egos. He truly sought out input from everybody around him, even if he was the most qualified and had the most knowledge,” said Greg Regan, the labor federation’s elected secretary-treasurer.

Willis was particularly alert to the possibility a child-care problem might force a colleague to bring a child to work.

“You know when a dog hears a noise and his ears perk up and he’s getting ready to bark? That was Larry,” when there were kids in the office, said Shari Semelsberger, who began working with him at the Transportation Trades Department in 1999. Willis would set up obstacles and roll with kids on the office floor, she said.

The days around his yearly drive with his wife to take his daughter to Camp Echo in Fremont, Mich., where he once was a counselor, were among his happiest, Semelsberger said. “He absolutely loved life. He adored his daughter and his wife,” she said.

York said Willis “always joked that he had kids so he could send them to his camp,” and making it there each year represented a homecoming that had deep personal meaning for him. His experiences there helped him grow into the giving and welcoming person he was, York said. “He would say, ‘I just want to touch camp,’ ” she said.

The family welcomes donations to Camp Echo in his honor, she said.