San Francisco transit officials voted Tuesday to add a new parking lane on Valencia Street to shield bicycles from cars, a design the city may replicate on other dangerous corridors.

The unanimous vote by the San Francisco Municipal Transportation Agency’s board of directors had support from Supervisors Hillary Ronen and Rafael Mandelman, hundreds of bike advocates and Mayor London Breed, who has urged the city to fast-track safety improvements that often get mired in politics or bureaucracy.

“We do not have time to waste,” Breed wrote in a letter to the board, championing the new bikeway configuration between Market and 15th streets. The board approved it after a tense hearing in which bicyclists implored the board for protection, while teachers and parents from a nearby school criticized the plan.

Officials will evaluate the four-block stretch for the next year and a half to determine whether it reduces injuries and forces drivers to be more careful. For years, the strip has been an obstacle course for bicyclists, jammed with delivery trucks and ride-hail cars that double-park to drop off passengers. Transit officials logged 81 collisions there between 2012 and 2016, a large share of the 268 reported on Valencia Street overall.

Bike advocates suspect the actual number of crashes is much higher, often going unreported. Many who spoke at Tuesday’s meeting shared emotional stories of being struck by cars and buses.

“I’m here in bursting support of this pilot,” said Paul Valdez, who described himself as a Valencia Street survivor.

But parents of kids at a Valencia Street Quaker school worried that the city is redesigning the street for bikes at their children’s expense. San Francisco Friends School enrolls 450 students, and many of them get dropped off and picked up in cars.

While a few parents — and one Friends School sixth-grader — championed the protected bike lanes as a safer route to school, most feared that students would be mowed down in the crosswalk by a bicycle.

The notion of bicyclists and students being pitted against each other made several speakers cringe.

“This is intensely uncomfortable for me,” said Michael Feldman, a Friends School parent who urged the board to reconsider the plan.

Though the parents expressed concern for bikers’ safety, Feldman and others were adamant that the proposed lanes don’t do enough to protect kids. “The fact is that kids are space cadets, and the odds of a kid doing something stupid and getting in the way of a bike are 100 percent.”

Such appeals didn’t persuade the SFMTA board to stop the project. Chairwoman Cheryl Brinkman, an avid bike commuter, said she’s confident in cyclists’ ability to be vigilant and stop for children.

Rachel Swan is a San Francisco Chronicle staff writer. Email: rswan@sfchronicle.com Twitter: @rachelswan