Against the backdrop of an ongoing Federal Transit Administration safety inspection, the MBTA board approved a $9.6 billion five-year capital investment plan Thursday that outlines more than 500 projects throughout the transit system.

The plan sets aside nearly $2.4 billion for new vehicles, including double-decker commuter rail cars, new Red and Orange line trains and hybrid and electric buses.

About $2.2 billion will go toward projects that include track and signal replacement, expansion of the bus lane network as well as Green Line safety improvements. More than $1 billion will be spread across 87 passenger facility projects that focus on accessibility improvements, elevator replacements and platform upgrades.

In fiscal year 2019, the MBTA reported spending an unprecedented $1.9 billion on capital projects and set a goal to spend $2 billion in fiscal year 2022. The T plans to spend at similar levels in FY2023.

Matthew Petersen, with the advocacy group TransitMatters, said the T needs to do more than spend. He would like the agency to improve the way it communicates with riders about how they will benefit from capital investments.

“The goal of a capital program should not be to spend money,” Petersen said. “The goal of a capital program should be to invest in and improve service.”

Brain Kane, executive director of the MBTA Advisory Board, praised the capital investment plan as a “great place to start.” But he expressed concerns about affordability, citing the T’s plan to borrow money to pay for the upgrades.

Kane said the T is $7.6 billion in debt, and plans to borrow an additional $600 million each year. The agency expects to use money from its operating budget — between $200 million and $300 million — to pay back the debt.

“This is money that is not spent moving people on buses, trains, subway cars and paratransit vehicles, ferries, etc.,” Kane said.

He called on the transit agency to be aggressive in applying for federal grants, and said the state legislature should direct more funding to the T.

The five year investment plan includes roughly $7.5 billion for projects related to safety, which has been an issue for the T. Over the last year, a series of incidents have resulted in injuries and even some deaths.

Those incidents prompted the FTA to conduct a safety inspection of the T. In an April letter to T General Manager Steve Poftak, the federal agency cited extreme concern with “ongoing safety issues” at the T and said it “remains unclear what actions the MBTA Board and executive team are implementing to prevent and address the system’s safety violations.”

Poftak said Thursday that the agency has had “an extensive series of interviews” with FTA officials and is now “in the middle of a number of site visits.” A report from the FTA’s inspection will likely be released this summer, Poftak said.

“This is really an opportunity for us as an organization to learn and to get a thorough assessment of the places where we may be doing well in terms of safety,” Poftak said. “But I think more importantly, the places where we have a deficit and that we need to improve our processes.”

The FTA’s intervention followed a fatal incident in which 39-year-old Robinson Lalin was dragged to his death after his arm became caught in the door of a Red Line train. Preliminary reports from the National Transportation Safety Board and the MBTA revealed that a short circuit in the door’s control system allowed the train to move even though it was obstructed. The train car involved in the incident was more than 50 years old.

MBTA board chair Betsy Taylor said even though “many thousands of people ride the T safely each day, too many tragic accidents have occurred of late.”

“The board and I welcome the findings of the FTA and the comments and suggestions of other parties,” Taylor said. “We will do everything in our power to implement those recommendations as expeditiously as possible.”

The T expects to replace its entire fleet of Red Line trains by 2024. So far, 10 train cars have been delivered, six of which are in service, according to a T spokesperson. A new fleet of Orange Line trains is expected next year. Seventy-four of those cars have been delivered, and 64 have been available for service, though not all at the same time.

The T recently removed new Red and Orange line trains from service after the failure of an Orange Line car’s braking system last week.

The T’s preliminary findings showed a bolt in one of the car’s braking units was not “properly installed at the manufacturing plant.” After an inspection of 57 cars, the agency said it found improperly installed bolts on six Orange Line cars and one Red Line car.

The bolts were fixed and the cars are back in service, according to a T spokesperson. Poftak said the T has taken additional steps to make sure the bolts are properly installed on all new trains moving forward, and in-service cars will be inspected every two weeks until an engineering investigation wraps up.