A top MBTA official remains unsatisfied with the bus fleet performance, slamming the on-time rates Monday as "abysmal" after raising similar concerns several times in recent months.

Fiscal and Management Control Board Vice-chair Monica Tibbits-Nutt, who also serves as executive director of the 128 Business Council, renewed her criticism of how the T's buses have fared during a presentation about the Better Bus Project, which aims to improve service by redesigning routes.

Since the first round of changes went into effect in September, on-time performance has improved, but both key and non-key routes still lag below their targets.

Key routes, considered on time when they depart within three minutes of the scheduled trip, hovered roughly around 77 percent on-time performance in November compared to a target of 80 percent, according to the presentation.

Non-key routes ran on-time just above 60 percent in November despite a 75 percent target and a 70 percent minimum policy standard.

"This on-time performance is awful," Tibbits-Nutt said. "Whenever the commuter rail even gets near 80 percent, we drop everything, we start doing every possible thing we can, and yet we're letting our bus riders exist in this on-time performance."

Tibbits-Nutt has been vocal this fall about problems with the T's buses. In October, she described bus performance as "beyond unacceptable" and requested Deputy General Manager Jeff Gonneville return with an "actual plan" for improvement. During a November vote about upgrading the commuter rail, Tibbits-Nutt also pushed for creation of a bus transformation approach.

On Monday, she said she was frustrated to raise similar points once again.

"This is abysmal, and I asked the deputy GM to come back and tell me what was going to be done about it, and it doesn't look like we once again still have a plan of what we're going to do about it," Tibbits-Nutt said. "I just don't know how we continue to go out to our riders and ask them to be patient on all of these things, and this is the type of service we're delivering if you're a bus user."

Kat Benesh, the MBTA's chief of operations strategy, policy and oversight, told Tibbits-Nutt that there is no "silver bullet" because every route needs its own unique solution.

Benesh's presentation included several possible paths forward. She said bus lanes can improve reliability significantly, and an upcoming capital investment plan may include a $50 million "challenge fund" to encourage municipalities to create bus lanes.

The T will also work to ensure at least 90 percent of its bus trips start on time — only 71 percent did so in September and October — but may need to make "scheduling and asset tradeoffs" in how frequently buses run to reach that goal, she said.

Gonneville said the operations department plans to request additional supervisors and dispatchers to help boost performance.

"We have found, looking back, a number of areas where we can make improvements, both from the management staff and, as you and Kat were discussing, with dispatch," he told Tibbits-Nutt. "Additional dispatchers will be part of our request going to the bus transformation team that's been assembled."

Another round of route changes is scheduled for Dec. 22.