Louisa Gag was devoted to making city streets a safer place for everyone. And her death this week as she rode her bicycle on those streets is reminding many that more progress is necessary to avoid tragedies.

Gag was struck and killed by a person driving a truck on Thursday while riding her bicycle on Tremont Street, near the Roxbury Crossing MBTA station.

She worked as a transportation planner for the city of Boston, expanding the city’s public bike share program. Prior to that, she spent years as an advocate with the LivableStreets alliance. In 2017, Gag coauthored that group’s plan to help cities achieve a goal of eliminating traffic deaths and serious injuries.

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And as activists who worked alongside Gag process their grief, they say there was so much more for which she should be remembered.

“In moments like these there is a tendency to reduce the person to the way they died and to their activism,” said Stacy Thompson, former executive director of LivableStreets. “And so while we may know Louisa as a deep champion of the city and a close advocate, she’s also a Boston Latin [School] kid. She’s also, like, the most infectious, hilarious person you’ve ever met. She’s also a daughter. It’s so important to us right now for her life to not be reduced to how she stopped living.”

Several people who worked alongside Gag described the joy she brought to everything she did — even at difficult moments.

“When I think of Louisa and I think of the hard work and the passion that she brought — she always did it with a smile,” said Galen Mook, executive director of the Massachusetts Bicycle Coalition.

And that passion went well beyond making the city’s streets safer, Mook said.

“She had a conviction of bettering the world,” Mook said. “We knew her in the transportation sector, but I think her passion really was to make a better society. And we were so lucky that she landed in our sphere. She was a champion at whatever she wanted to put her work into, and her life and her passion into. And it really was to make the city better, to make our world better, more equitable, more safe, more welcoming, more friendly.”

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Gag began working for the city in 2022 after the city announced plans to expand the public bike-share program, Bluebikes. Kim Foltz, director of the Boston Bikes in the city’s Streets Cabinet, hired Gag for the job.

“She just took on the management of that project with such incredible drive and determination, but also her skills and talent in engaging with communities and navigating through the challenges that are inherent in anytime we’re making changes to streets,” Foltz said. “She was just incredibly gifted in that work.”

Foltz recalled a recent meeting in which residents were angry about the loss of parking spots as a result of a new Bluebikes station.

“And she was able to just connect with them immediately, and just let them know that they were heard, but still sort of say in this incredibly graceful and gentle way, ‘This is a public street, and parking is something that we have to balance in addition to other needs for the curb use.’ And where other people might get angry or frustrated when confronted with people in opposition, she was able to just sit down face to face and say, ‘I hear you, and here’s where we’re coming from.’”

Gag was remembered in a written statement by Boston Mayor Michelle Wu.

“I am heartbroken by the passing of Louisa Gag, a dedicated public servant whose life’s work was making our streets, neighborhoods, and public spaces safer and more accessible for everyone to enjoy,” Wu said.

Wu described Gag, who grew up in Roslindale, as a “bright light in our community,” who first worked with Wu as a policy fellow in her city council office.

“She quickly became a trusted colleague and partner. I am absolutely devastated by this unfathomable loss for our community and our City. I will miss her terribly,” Wu said. “Louisa led programs and improvements that made our streets safer, our communities stronger, and our residents’ daily lives better. Her legacy will endure in the work she advanced across the City, and in the commitment of her colleagues, friends, and fellow advocates to carry it forward.”

Thompson said some might expect that groups like hers “are going to immediately turn this into advocacy action and turn her into a martyr.”

But their advocacy looks the same today as it did before the tragedy, she said.

“The asks are the same. The level of danger is the same in the city. And we hate that this moment is when people are waking up to it.”

Traffic accidents claimed the life of nearly one person a day in Massachusetts last year, said Brendan Kearney, executive director of the advocacy group WalkMassachusetts.

“At least 351 people died in traffic crashes across all modes, all across the state,” Kearney said. “And Massachusetts is one of the quote-unquote safe states, if we’re looking at across the country,” he said. “The number of people that are grieving Louisa right now, like, multiply that by 351 every single year. It’s overwhelming, and it’s really sad.”

“Beyond the grief and the sadness, there is palpable anger because we know that these are preventable,” Mook added. “We know that there are solutions. We know that steps need to be taken, that leadership needs to be made. That dollars need to be spent and it’s all well worth it because we are losing people on our roadways and we do not have to.”