The MTA released a financial plan through 2020 this week, and with it a reminder that bus and subway fares will likely increase in 2017, and again in 2019. Overall, the MTA is planning to generate an extra $308 million annually, next year through to 2020. In a statement Wednesday, the authority said that fares and tolls will increase next year "no more than 4%."

How these projected fare increases will hit straphanger wallets is less clear. "The MTA said yesterday that it projects at this point that it must increase revenue from fares by 2017—as was long announced and previously planned," said spokeswoman Beth DeFalco on Thursday. "However, we have not projected how that will be done and what fares will look like."

Still, there's room for informed speculation.

"Transit is always tricky because there's a balance between raising the time-based MetroCards—the weeklies and monthlies—and raising the base fare," said William Henderson, director of the watchdog group Permanent Citizens Advisory Committee to the MTA. "They could take the base fare up again, or they could do it by raising weeklies and monthlies, or they could do both."

In 2015, the MTA took the all-out approach: the base fare increased from $2.50 to $2.75. Unlimited 30-day passes jumped from $112 to $116.50, and 7 day passes from $30 to 31.

"The whole fare thing is sort of like the Rubik's Cube," Henderson added. "Moving one thing effects the other things."

This week the Daily News talked to the nonprofit Citizens Budget Commission, which analyzes government finances. The CBC pointed out that if previous fare hikes are an indicator, the single-ride fare might increase to $3. Henderson agreed on Thursday, hedging that the prediction assumes the unlimited MetroCards hold steady. "I think $3 is a viable option if they want to raise fare yields by 4%," he said. "That would just about do it more or less."

If the increase only hit the monthly unlimited MetroCards, those fares might increase to just south of $130 per month. There's a chance it could hit both, to lesser degrees.

Before anything is set in stone, the MTA will take public comment. "In the fall," the authority stated, "the MTA will present specific proposals for the 2017 all-agency fare and toll increases and will hold a series of public hearings to seek public reactions to the proposals."

In the meantime, advocates are concerned that Governor Cuomo's $8.3 billion commitment to the 2015-19 Capital Plan still lacks a definitive source and specific time frame for payout. (It costs the MTA about $15.6 billion a year to run, about $8 billion of which comes from fares and tolls.)

"We got very specific commitments not merely from the state government, but from the mayor of New York City as well," countered Cuomo-appointed MTA Board Vice Chairman Fernando on Wednesday. "Their word is good enough for me."

Riders Alliance Campaign Manager Rebecca Bailin wasn't assured. "If the state doesn't put in the money and put in sustainable sources of revenue to fund the MTA, it's going to come out of riders' pockets," she predicted. "And on top of that, we're going to have worse service."

Bailin added that even small fare increases—a 4% hike every two years is roughly apace with inflation—can be a burden. "If we have regular fare hikes that are more or less in line with inflation, that's still going to burden low-income people the most," she said.

In April, the Riders Alliance launched a campaign for half-price MetroCards for the city's working poor.