BART is proposing fare increases at a time when riders are dropping off, a trend that’s spurred tense arguments over how to make the transit system more palatable. It’s also accelerated BART’s efforts to force people to pay.

Strained by lost revenue and heightened demands to hire police officers, the Board of Directors is considering six years of incremental 3.9% fare jumps, based on inflation. They would start in 2022 and continue every two years until 2028, amounting to 16% over the entire period.

That’s on top of a 5.4% spike — adding about 40 cents to every one-way trip from Antioch to Embarcadero — that will take effect in January.

BART relies on fares for two-thirds of its operating costs, and it tries to squeeze passengers gradually, rather than hit them with abrupt, dramatic hikes. In the past, BART didn’t always keep pace with changes in the value of the dollar, officials said.

With the specter of higher fares looming, the board is also poised to offer discounts to low-income passengers, which will cost about $4 million a year. An additional youth discount, which is already established, costs $3 million a year.

The prospect of helping one group of riders, while raising the price for others, made one director uneasy during a budget presentation Thursday.

“With ridership dropping and satisfaction dropping, now is not the time to raise fares at the same time that we’re giving a discount,” said Director Debora Allen.

Although the low-income assistance program seemed to have wide support, other directors shared Allen’s concerns that higher fares would only chase more riders away. Director Mark Foley said he wasn’t comfortable making a decision next month that would affect passengers for nearly a decade.

“I don’t want to tie the hands of future board directors,” Foley said, adding that he’d prefer to have the board revisit ticket prices every two years, rather than rely on a “crystal ball” several years out.

The discussion came as BART faced tough choices about its budget. The agency had to cut $17 million across all of its departments this year to account for rising costs and a decline in operating revenue. Riders are peeling off to Uber and Lyft, particularly on nights and weekends. Pressure is mounting on BART to crack down on drug use and transients.

But the board and agency staff are wrangling over how to tackle these issues. The budget called for an additional 19 police officers and four fare inspectors to keep interlopers out of the trains and stations. Yet some directors want a different solution: civilian ambassadors.

If BART ditched the additional fare inspectors it could save $500,000 annually, enough to start an ambassador program, Director Rebecca Saltzman said. She’s among a board faction that’s urging the transit system to shift focus, from traditional law enforcement to something more akin to community policing.

Director Janice Li concurred. “I don’t tie fare evasion to all the other quality-of-life issues,” she said. “We don’t know why people fare evade.”

Other directors disagreed, saying BART needs to stave off cheats if it’s going to solve a multitude of other problems — including the slow bleed of paying customers.

“I recognize that fare evasion is interrelated with the impasse of homelessness and opioid abuse,” said Director Robert Raburn. Allen said it’s “pretty well established” that criminals, drug users and panhandlers aren’t paying to get into BART.

Whether the scofflaws are committing crimes or not, BART is intent on keeping them out. To that end, the board looked at four options for sturdier gates on Thursday.

They include New York’s “Iron Maiden” — thick, prison-style bars that come together like interlocking teeth from floor to ceiling.

A cheaper and more realistic alternative is the “stacked’ or “cinched” gate, a slight modification to the existing consoles. BART engineers are already toiling away at these models, which could include a shoulder-high gate placed atop a waist-high gate, a gate with higher air pressure to prevent people from prying it open, or a gate with a metal shark-fin plate that pops up when the wedges close, making it harder for people to vault over them.

The stacked gates will appear at Richmond Station this summer, while the pop-up version will debut at Fruitvale. BART is already testing cinched gates at Antioch, Pittsburg Center and Embarcadero, three stations that are known for heavy fare evasion.

Modifying the existing 600 gates in the transit system would cost about $15 million, while replacing them could cost up to $135 million. In addition to the Iron Maiden, BART is also contemplating tall panels, made either from Plexiglas or rubber coated in plastic.

The board also decided Thursday to start an analysis on new fares for its Silicon Valley extension , anticipated to open by the end of the year. The agency is considering a $7.75 one-way ticket price from Embarcadero to the Berryessa Station in North San Jose, or $15.50 round trip.

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