MBTA OFFICIALS RELEASED FIGURES on Monday indicating the agency’s bus system, which carries up to 450,000 people on a typical weekday, is unreliable a large amount of the time and needs significant redesign and investment to upgrade performance.

Using data from October, officials told the Fiscal and Management Control Board that the bus system is reliable – meaning it arrives on time at key measuring points along the 170 routes – only 65 percent of the time. On the Silver Line and the 15 busiest routes, which serve 40 percent of the system’s riders, buses were reliable 75 percent of the time. All of the remaining routes on the system, serving 60 percent of riders, were reliable only 58 percent of the time.

Jeffrey Gonneville, the T’s deputy general manager, said the 58 percent figure was disappointing. “That is a staggering number. That is a concerning number,” he said.

T officials said their target is 80 percent reliability for the Silver Line and the 15 key bus routes, with a minimum goal of 75 percent. The October data indicate three of the routes exceeded the target, six came in between the minimum goal and the target, and nine were below 75 percent.

For all the other routes, the target is 75 percent reliability with a minimum goal of 70 percent. Using that measuring stick, the officials said only six routes exceeded the target, nine were between the minimum goal and the target, and 128 were below the minimum goal.

Jess Casey, the deputy chief operating officer of service planning and strategy, said she is leading an effort to develop a service plan to improve bus run times, reliability, comfort, and frequency. In addition, T officials outlined a plan to spend up to $1.3 billion buying new buses, $218 million overhauling existing buses, and $808 million building new and repairing old, rundown maintenance facilities.

The service plan, scheduled to be completed by the end of next year, involves the creation of new bus schedules, the coordination of traffic lights to give buses priority at intersections, and the development of dedicated travel lanes for buses.

All of the measures are designed to fend off the loss of riders to other modes of travel, particularly transportation network companies such as Uber and Lyft. T officials say bus ridership has fallen 6.5 percent over the last three years. Most of that dropoff came in the most recent year when buses carried 5.6 percent few passengers on weekdays, 9.9 percent fewer on Saturdays, and 9.14 percent fewer on Sundays.

The T has already had some success coordinating travel signals to give buses priority at intersections, but wants to expand that effort to many more bus routes and many more communities. Progress has been slower on dedicated bus lanes, but Casey said the results from a test on Broadway in Everett are promising. She said a dedicated lane there caused bus run times to drop 18 percent before 9 a.m. and 30 percent in the peak rush hour between 7 a.m. and 8 a.m.

Casey said MBTA buses operate in 50 municipalities, so progress on coordinating traffic signals and instituting dedicated bus lanes will depend on MBTA officials working closely with their counterparts at the local level. She said the T has hired a director of operational outreach and strategy to lead that effort. The person, who has been doing similar work in Seattle, will start work later this month, she said.

Bill Griffiths, the T’s senior director of fleet strategy, said the agency has 988 buses – 887 40-foot buses and 100 60-foot buses. He said the T has nine bus maintenance garages, all of which are operating at capacity and many of which are in poor condition. Griffiths said he was shocked at the inadequacy of the Quincy garage and Joseph Aiello, the chairman of the control board, called the situation at the garages “deplorable and unacceptable.”

Griffiths recommended that the T over the next 15 years replace and expand its bus fleet and repair or replace all of its maintenance garages. He said the T should immediately replace 194 buses, spend $218 million overhauling some existing buses, and negotiate a longer-term contract for the delivery of 100 new buses a year. Ultimately, he said, the T should purchase 1,200 to 1,350 new buses at a cost of $1.1 billion to $1.3 billion.

T officials said the new buses should run mostly on electricity to reduce carbon emissions. Using $10.1 million in federal grants, they have ordered five, 60-foot, battery-operated buses that should be delivered next year, and they are developing a new type of hybrid, 60-foot Silver Line bus capable of running on batteries inside the tunnel from South Station to the Seaport District and then converting seamlessly to diesel without having to stop. T officials also hope to entice electric bus manufacturers to test a 40-foot, battery-run bus on a route in North Cambridge that, if successful, could lead to a long-term procurement.

Griffiths recommended the T spend $808 million expanding the Southampton bus maintenance garage, rehabbing the Cabot and Charlestown garages, and building four new garages. He said six existing Quincy, Albany, Arborway, Lynn, Fellsway, and North Cambridge garages should eventually be closed.

A lot of work remains to be done on improving bus service and Transportation Secretary Stephanie Pollack said there isn’t a lot of time if the work if the work is going to start next year. Casey said she hoped to have a final service plan ready for approval by December 2018, but Pollack said some aspects of the plan should probably be rolled into the budget for fiscal 2019, which will be put together at the start of next year. Similarly, T officials urged Griffiths to quickly finalize his fleet plans so the Fiscal and Management Control Board can act on them.

MBTA General Manager Luis Ramirez said the proposals to improve the MBTA’s bus service have have tremendous potential. He said bus improvements could have “ the biggest impact to ridership in the next 24 months.”