A KEY MEMBER of the MBTA’s oversight board raised concerns on Monday that spending at the authority is rising at an unsustainable pace.

Brian Shortsleeve, a member of the Fiscal and Management Control Board who previously served as general manager of the T, pointed out during a presentation on the upcoming fiscal year’s budget that expenditures are rising as the agency bulks up but the number of passenger trips provided by the authority is static or trending downward.

Shortsleeve said the agency will make it through the coming fiscal year with an infusion of cash from the governor and the Legislature and rising sales tax revenues, but if the economy takes a nosedive the authority could be in trouble. “We’re going to have a cost structure than can never keep up,” he said.

The debate about sustainability surfaced during discussion of a narrowly balanced budget plan for fiscal 2021, which begins July 1. The control board unanimously approved a preliminary version of the budget and sent it off to the MBTA Advisory Board for review. The budget ups staffing considerably for safety and infrastructure work and adds employees to expand bus and subway operations. Overall, 333 additional workers will be added in those areas.

The control board amended the budget proposal to include additional funding for the hiring of at least one staff member to start developing a fare system based on a rider’s ability to pay. Chrystal Kornegay, the control board member who proposed the amendment, said planning needs to begin in fiscal 2021 if a means-tested fare system is expected to launch in fiscal 2022. The board approved the amendment unanimously.

The budget documents indicate the transformation of commuter rail system into a more subway-like operation will begin this year with the hiring of five new workers at a cost of $800,000, or an average of $160,000 per employee. No additional staff is forecast in fiscal 2021. T officials have been slow in rolling out their plan for the $1 billion-plus commuter rail makeover.

The T plans to roll out 60 new buses this fall to beef up rush-hour service and launch several scaled-back expansion initiatives.  The new expansion initiatives would create high-frequency service on the bus-only lanes in Everett and Somerville (Routes 104/109 and 89/101), add a bus along Route 112 through Everett and Chelsea to increase service frequency, expand service on Route 31 between Mattapan and Jamaica Plan, and add weekend service on Routes 116 (Maverick Station on the Blue Line to Wonderland) and 117 (Lynn to Haymarket).

During the public comment period before the meeting, union officials and transit advocates complained that the T has cut its front-line maintenance workforce by 20 percent since 2015. A handout said that information came from a report issued by an outside safety review panel in December. That specific claim is not contained in the report, but the document does blame a decline in maintenance work for many of the safety problems at the authority.

Poftak, the T’s general manager, disputed the notion that the T is cutting the number of employees. He said the agency expected to add a record 1,000 employees this year. In January, he noted, the T hired 111 new employees, its highest monthly hiring figure in five years. “It’s important to set the record straight here,” he said.

T records, however, indicate the workforce size is 6,301 right now, only slightly more than the 6,270 it was in fiscal 2015 when Gov. Charlie Baker came into office. Over the intervening years, the workforce hit a low of 5,643 in fiscal 2018 before climbing back to its current level.

Shortsleeve’s comments about sustainability come at a time when Baker says the T doesn’t need additional funding beyond what he has proposed, while the Legislature is pushing forward with plans for a sharp increase in transportation funding. The House last week approved legislation that would increase transportation funding by $600 million a year.

According to the T’s performance dashboard, the T’s operating expenditures (not including the cost of debt service) in fiscal 2021 are forecasted to be $1.8 billion, up $267 million, or 17 percent, from what they were in fiscal 2018. The average number of weekday trips provided by the agency, however, has fallen from 1.23 million in November 2017 (which is part of fiscal 2018) to 1.18 million in November 2019 (which is part of fiscal 2020).

Shortsleeve, who tends to focus on keeping the agency’s expenses in check, said the T needs to come up with a way to boost productivity, reducing the cost per trip. Steve Poftak, the current general manager, said trips are not the only measure of productivity at the agency. He said the agency is developing systems to evaluate productivity in a number of ways.

Transportation Secretary Stephanie Pollack said Shortsleeve makes a good point. “We can’t just pay more money for the same thing,” she said. “What are we getting from these investments?”

The control board has taken no official position in the Beacon Hill debate over new transportation. Three members of the five-person board – Joe Aiello, Monica Tibbits-Nutt, and Brian Lang, have urged the Legislature to increase spending, while the other two members — Shortsleeve and Chrystal Kornegay — have remained largely quiet. All of the members are Baker appointees.

After the meeting, Shortsleeve said he had no position on the transportation revenue package approved by the House last week. “I don’t offhand,” he said.  “Our focus here is making sure that this organization is driving toward better service but also doing it in a fiscally responsible way.”