As the push for safer bike paths gains momentum in San Francisco, cyclists are eyeing a busy waterfront boulevard once crisscrossed by a double-decker freeway: the Embarcadero.

Cycling advocates want concrete barriers around the bike lane that snakes from South Beach Park, near the baseball stadium, to Pier 39, covering 2.5 miles on the northeast edge of the city. Thousands of cars zoom along Embarcadero to and from the Bay Bridge, while Ubers and Lyfts orbit the blocks, and cruise ships disgorge hundreds of tourists at a time. So the cylists want the lane to be fully separated from traffic.

Officials at San Francisco Municipal Transportation Agency began discussing this Embarcadero Enhancement Project in 2014. But so far they have committed to building protective bike barriers on just two portions of the road: from Mission to Folsom streets — which could extend south to Harrison Street — and along the cruise ship terminal at Pier 35. These will be enclosed, two-way bike paths only on the water side, replacing green-painted lanes. Planners pledged to complete those segments this summer, while the rest is a tantalizing possibility that still lacks funding and may require an environmental review.

On Tuesday, transportation agency staff will ask the Port Commission for feedback not only on the planned bike barriers, but also on the prospect of building them along the entire Embarcadero.

For a city trying to balance the needs of many, a protected two-way bike lane along the full, chaotic strip could be a rousing political statement. It would require controversial trade-offs, including, possibly, the removal of a northbound traffic lane and up to 100 parking spaces. Northbound car traffic above Broadway would have to narrow from two lanes to one, SFMTA Director Jeffrey Tumlin said Friday.

Businesses in the popular tourist district are muttering about concerns, even as advocates tout what they say is a visionary street design for San Francisco.

“This has very much been our dream and our members’ dreams,” said Melissa Lewis, spokeswoman for the San Francisco Bicycle Coalition. The group has lobbied for a protected Embarcadero bike lane since 2014, the year the Port and San Francisco Municipal Transportation Agency began hosting workshops to discuss the roadway’s future.

Both agencies govern the thoroughfare, with port officials leasing property and managing sidewalks, while transportation staff controls streets and traffic signals. They have to make decisions together, a process that has sometimes required extensive compromise. Last week, board directors at SFMTA gushed over the full 2.5-mile protected bike lane extension. A spokesman for the port said the project’s “time has come,” although commissioners may raise new questions at Tuesday’s meeting.

Now, as transportation officials bubble with enthusiasm about the recent car ban on Market Street, some view Embarcadero as another boulevard that’s ripe for change. And those who want a more bike-friendly waterfront want to see it done quickly.

But to do that, the logistical hurdles are steep and the politics formidable.

“Absolutely, I support it,” said SFMTA board Director Cheryl Brinkman. She believes that almost everyone — tourists, conventioneers, pedestrians, businesses and cyclists themselves — would benefit from a wide two-way bike path surrounded on both sides by a moat of concrete. The main challenge, she said, is that “if people don’t see other street designs like this around the city, they don’t understand that it can work.”

Merchants and neighborhood groups are skeptical.

Among those caught in the debate is Pete Sittnick, a managing partner at Epic Steak and Waterbar, two restaurants nestled beside the bow-and-arrow sculpture in Rincon Park on the Embarcadero. Waterbar has drawn scorn from the cycling community because its valets have to drive across the bike lane to pick up and drop off customers. Speaking at an SFMTA board meeting last week, Sittnick emphasized his support for bicycle safety and said he wants to be a good neighbor.

But in an interview with The Chronicle, he voiced concerns that a dramatic reconfiguration of the street could cost him customers.

“Between the dining room and the bar, we probably serve 1,500 to 2,000 people a day,” he said. “So I have a commitment to those guests. And I have an investment group that’s obviously looking for a return. I have to be able to make money to pay off that investment.”

He added: “Let’s say the valet lane went away, and it became just a bike lane. That would hurt me. It would make it less convenient and less accessible. Then people would think about how often they came.”

Sittnick is far from alone. Some 30,000 cars travel each day along the busiest sections of the Embarcadero near the Ferry Building. The road is a vital connector to the Bay Bridge, as well as to baseball games at Oracle Park, taffy barrel shops and sea lions at the wharf, popular seafood restaurants, and the nearby Financial District.

The cruise ships require significant loading zones — each one equates to parking an 800-unit apartment complex for a day at Pier 35, between Bay and North Point streets, said Casey Hildreth, the planner at SFMTA who is leading the Embarcadero project.

Pier 39 alone draws 15 million visitors a year, and 35% to 50% of them arrive by car, said Taylor Safford, the pier’s president and CEO. Safford likes the concept of a protected bike lane, and said he’s open to eliminating the third traffic lane below Broadway as well as parking — if a traffic study shows that it makes sense.

But constricting car traffic could present problems for San Francisco’s most popular tourist attraction, he said.

“You can’t tell people in outlying areas ... that they’re going to have to park in Candlestick Park and take a bus into the city” to visit the wharf, he said. Losing parking spots along the Embarcadero might not affect Pier 39, which has its own garage, but could harm entities farther south, such as the Exploratorium, Safford said.

Another complicating factor is San Francisco’s multibillion-dollar plan to fix its crumbling seawall. It could require crews to dig up the road and undo any changes that transportation officials make to the pavement, said Supervisor Aaron Peskin, whose district includes the northern stretch of the waterfront.

Peskin supports temporary measures, like plastic posts or removable concrete islands, to insulate the bike lane from passing cars. Transportation credos have evolved since 1991, he said, when 20,000 residents signed an ill-fated petition to preserve the elevated Embarcadero Freeway after it was damaged in the 1989 Loma Prieta quake.

Sometimes it’s taken a tragedy to change minds.

Nearly two years ago, pedicab driver Kevin Manning was struck and killed by a car while squiring a family of tourists on the Embarcadero near Sansome Street. His death became a galling illustration of the city’s inability to shield cyclists from danger. All eyes turned to the pristine promenade by the bay, where bikes and pedicabs jostle daily with cars and trucks.

“I’ve seen a lot of close calls with those Blazing Saddles bikes,” Lewis of the Bicycle Coalition said, referring to a popular bike rental for tourists. Lewis bikes part of the Embarcadero each day to get from the Ferry Building to the Bicycle Coalition office on Market Street.

Last year the SFMTA enacted a “quick build” policy at the urging of Mayor London Breed, which allowed the agency to make fast changes to streets without slogging through months of legislative review. Staff members have used the policy to design and plan the two segments they will build this summer, pending a sign-off from the port, Hildreth said.

Supporters of the full Embarcadero bike lane project wonder why the agency can’t apply this quick-build method for 2.5 miles. That’s not so easy, Tumlin of the SFMTA cautioned at the meeting Tuesday. The Embarcadero is a busy, complicated spine, and any change to its geometry could consume the agency’s time and attention, at a time when it’s struggling to hire staff and complete other projects. And it might have to be redone to accommodate a new seawall.

Malcolm Heinicke, who chairs the SFMTA board, acknowledged those difficulties. Though he bullishly promoted car-free Market Street, Heinicke urges caution along the waterfront.

“This is certainly something I would be in favor of exploring,” he told The Chronicle. “But I don’t want to get out ahead of it.”

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