Teddy Einstein, a West Philly mathematician, was about to hit his stride. Then he was killed while riding his bike.

Eduard “Teddy” Einstein, a beloved professor and mathematician, was biking home from a haircut when a driver killed him earlier this month.

Einstein, 38, was struck and killed by the 18-year-old driver on Dec. 3 while riding his bicycle on Providence Road in Upper Darby. No charges have been filed in Einstein’s death, according to Upper Darby police, but an investigation is continuing, and police said the driver cooperated with police at the scene of the crash.

The West Philadelphia husband and father of two young children, Charlie and Lorcan, was known for his sharp wit, encouraging students, and scouring cities for the most interesting, and spiciest, foods. Einstein was, above all else, dedicated to his family.

“He didn’t need much more than me and the boys. It was like he was my home, and I was his,” Einstein’s wife, Ruth Fahey, 45, said. ”That’s kind of how we agreed that we would move around the country together as a family, and it was wonderfully freeing."

Born in Santa Monica, Calif., Einstein graduated from Harvard-Westlake School before receiving a bachelor’s degree in mathematics from Pomona College, a master’s in mathematics from University of California, Santa Barbara, and his Ph.D. from Cornell University. He would go on to hold postdoctoral fellowships at the University of Chicago and the University of Pittsburgh, where he taught, and most recently completed a three-year teaching term at Swarthmore College.

“He loved mathematics and wrote a first-rate thesis,” said Einstein’s Ph.D. adviser, Jason Manning. “Many mathematicians, even those who write a good thesis, don’t do much after graduate school. But Teddy’s work really accelerated during his postdoc at the University of Illinois at Chicago, and he was doing even more exciting work when he passed.”

His colleagues describe a mathematician working at, to put it simply, the intersection of algebra and geometry. Building on the work of mathematicians before him, including modern geometric breakthroughs in years past, Einstein studied abstract 3D shapes that cannot be visually represented in the real world. Work like that of Einstein and others contributes to a tool chest of solutions that scientists can use to study physics, neuroscience, and more.

“It is a terrible loss, especially to his family,” Manning said. “But also to his part of the mathematics community.”

As his term at Swarthmore ended earlier this year, Einstein had been working on research that was seven years in the making, Fahey said. This would help springboard him into the next chapter of his career.

Fahey said the day he was killed, Einstein was biking back from a fresh haircut to impress his potential new employers at Florida Gulf Coast University.

Mr. Einstein’s work ethic matched his appetite for camaraderie. He fed grad students out of his tiny Cornell kitchen and hosted a weekly trivia night. That is where he met Fahey. “He just loved to entertain with food,” she said.

Every week, he cooked for Fahey and the boys, from his prized favorites of Korean short ribs and fried chicken to testing out falafel recipes. A keg of home-brewed beer was always in the house so that Einstein could share his creations with friends. Fahey said his most recent yeast yield is still waiting to be processed.

Maddie Adams-Miller, who took Einstein’s math classes in her freshman year at Swarthmore, said her funny and wise math teacher never wanted to see a student fail.

“I loved talking to my friends from high school and telling them I had ‘Professor Einstein’ for math. Teddy always wore funny T-shirts to class and made a lot of jokes,” said Adams-Miller, now a senior. “When I was taking his course, I was struggling with my confidence and was not performing my best academically. Teddy reached out to me to offer support and genuinely wanted me to succeed in his class.”

An avid cyclist who biked everywhere and advocated for safer streets, Einstein was killed doing one of the activities he loved most. Philly Bike Action, an advocacy organization that Einstein and his wife frequented and his friend Jacob Russell organizes for, shared that he was hit by the driver while riding in an unprotected bike lane and wearing a helmet and high-visibility clothing.

“But there will never be a helmet strong enough or a clothing bright enough to make up for dangerous infrastructure. All Philadelphians deserve the freedom to travel without fear of tragedy,” the group said in a statement.

Russell believes safety improvements will not come solely from attempting to change laws or behavior, but rather by changing the road infrastructure, so that even “when mistakes happen, there aren’t tragedies,” he said.

Providence Road, where Einstein was hit and where he biked weekly, is considered a dangerous road by local planning commissions, appearing on the Regional High Injury Network map as a thoroughfare where multiple people have died or been seriously injured in vehicle, pedestrian, or bicycle crashes. Delaware County is currently in the process of onboarding most of its townships onto a “Vision Zero” plan to end all traffic fatalities by 2050 — similar to Philadelphia’s own Vision Zero.

The Delaware County Planning Commission said the county does not own the roads, which are overseen by the Pennsylvania Department of Transportation or specific municipalities; however, officials are “actively working to obtain additional funding for further safety improvements, and are continuing to work with our partners in our 49 municipalities on either our Vision Zero plan or to help them develop their own,” said Delco spokesperson Michael Connolly.

Fahey said she won’t rest until Providence Road’s lack of safety is addressed and will continue campaigning for safety improvements in Philadelphia.

A GoFundMe has been set up for Fahey to help fund efforts to protect Einstein’s legacy as a teacher and advocate, as well as to invest in campaigns to make streets safer, with an emphasis on the road where Einstein was killed. It has already raised more than $60,000.

In addition to his wife and children, Einstein is survived by his parents, K. Alice Chang and Thomas Einstein. The family encouraged people to donate to Fahey’s GoFundMe to honor Einstein’s legacy.