Banning cars on San Francisco’s Market Street may have once been a radical idea. But on Tuesday, the Municipal Transportation Agency board voted unanimously to do it, with undiluted support from just about everyone: bicycle activists, politicians, city bureaucrats, parents, health care workers, business owners, ride-hail companies and Mayor London Breed.

One message rang out loudly during a rally on City Hall steps and an hour-long hearing before the vote: start building “Better Market Street” immediately, and then replicate it elsewhere.

The plan that kicked off nearly a decade ago will start construction in January, with a ban on private cars east of 10th street on the city’s downtown spine. It will restrict commercial loading on the street to certain hours, extend the Muni-only lane from Third to Main Street, widen sidewalks, replace the ancient bricks with concrete pavers and add a sidewalk-level bike path with a protective curb. Crews will also build a streetcar loop east of United Nations Plaza, allowing the F line to shuttle from Embarcadero to Fisherman’s Wharf.

The first phase of this $604 million upgrade would extend from Fifth to Eighth streets, turning a strip of boarded-up storefronts into the locus of an urban renaissance. Ultimately, this collaboration between the city’s planning, public works and transportation departments will reconstruct the entire thoroughfare from Octavia Boulevard to Steuart Street, near the waterfront.

“It’s almost astonishing how well supported this is,” SFMTA board chair Malcolm Heinicke said before the vote. “Not just because it’s going to be beautiful and there will be trees. It’s supported because it will save people’s lives.”

Heinicke has touted Better Market for eight years, and on Tuesday he urged SFMTA to direct any available funds toward the project, so that it can beat its expected completion date of 2025. Market Street is among San Francisco’s busiest arteries, with 500,000 people walking along the strip daily and 650 riding bikes every hour during the peak commute. Its intersections are known for a high number of crashes that injure pedestrians and cyclists.

Once the redesign is under way, drivers who steer their cars onto Market will risk a moving violation. Cars will still be able to cross Market at intersections.

Breed joined the chorus of enthusiasm for Better Market, sending a letter to the SFMTA board on Monday to endorse the project.

“After a lengthy public planning process that included hundreds of outreach meetings and conversations with stakeholders, the city has developed a design that will support Vision Zero safety goals, improve transit and transform Market Street for our next generation,” the mayor wrote. She asked the agency to start building the infrastructure as soon as possible, using new “quick-build” policies to cut through the bureaucratic morass that often slows projects down.

Advocates want to spread this new vision of urbanism to other parts of the city. Even as the plans awaited approval, SFMTA staff were studying what other roadways and intersections could be made car-free, and advocates have plenty of suggestions. City Hall politicians support the concept, too: Supervisor Matt Haney has called on the agency to look at the Tenderloin neighborhood — a treacherous maze of asphalt in a neighborhood of residential hotels — as a possible candidate for its next makeover.

“When we have a city that’s grown this much, the streets are being pushed to the brink,” said Marta Lindsey, spokeswoman for the pedestrian safety group Walk San Francisco. “It gets to the point where everyone sees this is not working. We can’t have all these vehicles and humans co-exist, anymore.”

Besides transforming the landscape aesthetically, this new infrastructure would bring dramatic social changes to the street. Bicyclists would no longer be unceremoniously dumped into traffic east of Eighth Street, and Muni buses would no longer get stuck behind a person being chauffeured to work in an Uber.

Market Street has always symbolized the disorienting social inequalities of San Francisco, a tech hub where homeless people sleep on the sidewalks and high-rise offices are packed against vacant and dilapidated buildings.

Politicians, developers and urban planners have tried to revamp and revitalize the street many times over the years, but their efforts always seemed to fall short. The arrival of Twitter, resurrection of the Strand Theater and even the new canopies over BART stations did little to reverse blight that had built up for decades.

But none of the previous developments was as ambitious as the proposal going before SFMTA on Tuesday. Excluding private automobiles is “a bold statement” that would completely change the nature of the street, said Brian Wiedenmeier, executive director of the San Francisco Bicycle Coalition. It would be the most significant makeover of Market since BART began tunneling in the 1960s.

“Market Street is by design our central boulevard, and it could be ... a street that reflects the best of our values: community justice, sustainability, elevating people and their daily experience above cars getting someplace quickly,” Wiedenmeier said.

He added: “We have an opportunity to send a message nationally and globally that Market Street represents where San Francisco’s priorities are.”

Earlier this year, Heinicke directed staff to study other city streets and recommend which ones could go car-free. The board applied the idea to a block of Octavia Boulevard in July, prohibiting cars on a road that bordered Patricia’s Green.

Heinicke’s call for proposals spurred an animated conversation on social media. Twitter users came up with their own list, which crossed wide swaths of the city. It included the Tenderloin, Valencia Street, John F. Kennedy Drive in Golden Gate Park, and the northbound side of Embarcadero. Some of these roads are known for brutal crashes, like the 2016 hit-and-run killing of 41-year-old Heather Miller, who was pedaling down John F. Kennedy Drive when a driver veered into the wrong lane and struck her.

“There are some streets that are just so obvious,” said bicycle activist Matt Brezina. He founded People Protected, a demonstration in which participants form a human chain along bike lanes that lack barriers to separate them from cars.

Brezina said the conditions on Market Street inspired him to start attending SFMTA board meetings, back when the project was starting to gestate.

“I rode (my bicycle) on Market every day to get to the office,” he said. “And I would think, ‘Why is this street so broken?’”

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