The funds for the program are part of the $558 million Boston received from the American Rescue Plan Act, signed into law by President Biden earlier this year — more than $360 million of which has yet to be allocated, according to Sarah Anders, a spokeswoman for Wu.

Wu, who campaigned on making public transportation free, starting with bus service, has said she will work to secure long-term funding sources. At a hearing on Monday, the city’s director of strategic partnerships, Casey Brock-Wilson, said the city is keeping a close eye on the recently passed federal infrastructure law for potential financing opportunities.

Included in the $8 million budget is money to publicize the free service and also evaluate its effectiveness, Brock-Wilson said. It currently costs $1.70 to ride a local MBTA bus. Lisa Battiston, a spokeswoman for the MBTA, said by e-mail that “the MBTA will continue to have discussions with the city regarding any future fare-free expansions.”

Riders of the 23, 28, and 29 buses are primarily people of color who have low incomes, according to a 2019 report from LivableStreets, a public transportation advocacy group. The routes travel along or intersect with Blue Hill Avenue, where the city plans to install center-running bus lanes.

Since the city eliminated fares on the 28 bus this summer, ridership has soared. During the week of Nov. 15, the route carried 95 percent of its pre-pandemic weekday ridership, according to MBTA data maintained by the Massachusetts Department of Transportation. That’s up from 68 percent during the last week of August.

Other areas in Massachusetts are taking similar steps.

On Wednesday, the Merrimack Valley Regional Transit Authority’s advisory board unanimously approved eliminating fares across its fixed-route bus system for two years starting March 1 using federal COVID-19 relief funds. The agency serves primarily Lawrence and Haverhill.

At a authority board meeting Wednesday, administrator Noah Berger made the case for fare-free service, saying it would be more efficient to spend money earmarked for fare collection to eliminate fares altogether. Doing so would improve service and boost ridership, he said.

An agency analysis found that it took in $561,474 in fare revenue during fiscal year 2021, but only retained around $0.24 per dollar after accounting for the cost of collecting fares. Including the cost of updating the collection system, the agency would only retain $.08 per dollar, the analysis found.

“Fare collection is a very inefficient way of generating revenue,” Berger said in an interview. “It slows the bus ride down, it makes it less competitive. … If we’re able to speed up the route by allowing people to enter through all doors, that will allow us to put more service on the road for the same cost.”

Three of the agency’s bus routes have been free since September 2019 in a program funded by the city of Lawrence; all saw significant increases in ridership before the pandemic, Berger said.

The Worcester Regional Transit Authority first eliminated fares on its bus routes in March 2020. Earlier this month, the agency’s board voted to extend fare-free service through the end of 2022.

In Cambridge, the city is considering using some of its $65 million ARPA funds to provide fare-free bus service, said vice-mayor Alanna Mallon. Mallon said she has been in touch with Wu’s office about the 1 bus line and with Brookline officials about the 66 bus line. Both run from Cambridge into Boston and end in Roxbury, where they connect to the 23 and 28 buses.

“It’s all about how do we make sure we are using these funds to address the issues we saw very clearly during the pandemic,” Mallon said.