One out of every five Boston residents lives within a 10-minute walk of the MBTA's Fairmount Line and mayoral candidate John Barros called Tuesday for the T to use federal money to make the line more reliable, run more frequently and fully integrate it into the T's subway system.

Barros' call came as the U.S. Senate passed a $1 trillion infrastructure bill that is expected to provide Massachusetts with $2.5 billion to enhance public transit systems like the MBTA if it passes the U.S. House of Representatives. He said Tuesday that the money should be used to implement full rapid transit service on the Fairmount Line and other lines in Boston, featuring new electric trains, the same frequency as the subway system, and free transfers to buses or subway lines.

"Right now, with federal infrastructure funding on the verge of passage, we have a once-in-a-generation chance to deliver true rapid transit to neighborhoods in Boston that have been left out of past investments," Barros, who served as Boston's chief of economic development under Mayor Martin Walsh, said.

"Boston needs to be ready with shovel-ready projects, and I have a plan to transform federal funding into on-the-ground investments that will deliver increased access to jobs and mobility, create green jobs and training for local residents, and prepare our city for the effects of climate change while reducing our carbon emissions," he added.

In addition to the Fairmount Line improvements, Barros on Tuesday said he would also push for the T to deliver full rapid transit service along the Worcester Line from South Station through Allston-Brighton, extend the Orange Line from Forest Hills to Roslindale along the commuter rail's Needham Line, add a Neponset stop to the Red Line between Savin Hill and North Quincy, and build the Red/Blue Connector and a seamless connection between North and South Stations.

He also is interested in reactivating track service to the Seaport, and establishing a new commuter rail station and transit hub at Widett Circle to "solidify connections between the Fairmount Line and other lines to job centers" across Boston, his campaign said.

During an event at South Station after riding the Fairmount Line, Barros said he supports MBTA fare reform but not policies that other mayoral candidates support to make bus fares free. Instead, he said he is in favor of "a free/reduced fare program for low-income riders across all modes of transportation."

"Just making buses free doesn't help riders who have to transfer to the subway, and we shouldn't be subsidizing wealthy riders at the expense of much-needed investments in our transportation system," Barros said. "My fare reform plan calls for comprehensive income-based fares across the entire MBTA system, so that well-off riders keep paying their fair share, while lower-income riders get free or affordable access to the T whether you're taking the bus, the subway, or the commuter rail."