Mayor Martin Walsh on Wednesday sent a letter to MBTA leadership asking for concrete improvements to the train system to better service those inconvenienced by the still lagging Red Line.

“I just signed a budget for the City that gives $90 million to the MBTA--more than twice our own transportation budget,” he wrote to Transportation Secretary Stephanie Pollack. “As we know, the MBTA is not currently a functional service for many of the residents of Boston. Boston residents rely on the T to get to work, to take their children to school, to go to doctor appointments, grocery shopping, and live their lives--my residents need the T.”

Walsh noted the uncertainty on repair timing after a Red Line train derailed in June, which led to reduced service expected until at least Labor Day.

To bolster the line, Walsh asked for expanded Fairmount Line service, preserving the short-term express commuter rail train that rode alongside the Red Line, and increasing off-peak Red Line service.

The Fairmount Line should include eight additional weekday trips, Walsh said.

“The Fairmount Line has seen a noticeable increase in ridership during the last weeks, and the MBTA can increase service and capacity so more residents can utilize this line,” he wrote. “Additionally, riders should be able to use Charlie Cards on the Fairmount Line.”

This echoes comments from Rep. Dan Cullinane, who noted on Tuesday that the Fairmount had been a “lifeline” for Mattapan residents when the Red Line was out of commission. They and other elected officials are pushing for Charlie Card service on the Fairmount, which operates entirely within Boston but requires a commuter rail ticket.

Walsh also wants eight additional weekday trips among the South Shore Limited route that was added temporarily during the Red Line shutdown, which could scoot passengers in and out of Boston.

Noting expanded off peak service on the Orange Line to accommodate the Encore Casino, Walsh asked that Red Line service also run more frequently at off-peak hours.

These improvements could cost around $9 million annually if enacted, Walsh’s team estimates.

“Taken together, these service improvements would create a positive, immediate benefit for riders in Boston,” Walsh wrote. “We estimate that the total cost of these improvements is equivalent to a four month delay in fare increases and it’s only fair that any additional revenue be invested directly back into improved service.”