MBTA plotting a bus map of the future

Key bus routes like the 111 will likely go untouched, MBTA officials said.Jessica Rinaldi/Globe Staff/File/Globe Staff

MBTA leaders have launched a review of the agency’s bus network that could result in major changes to existing bus lines, including the addition of some new routes and the elimination of others.

The redesign of the bus system is part of the Massachusetts Bay Transportation Authority’s promise to vastly improve bus service. The goal, said state transit planner Scott Hamwey, is for the bus system to adjust to the way Greater Boston has grown and developed, and where people need to go.

The review will also consider service frequency and hours, in addition to the geography that the MBTA serves — or doesn’t yet serve. The T has a separate initiative underway to improve bus service on existing routes more immediately.

The T’s governing board began pushing for changes to the bus map soon after being appointed in 2015, inspired by similar initiatives in Houston, Seattle, and Baltimore, to combat declining ridership. On Monday, the board received an update on a plodding process that seems to be suddenly picking up steam.

The transit agency has about 175 bus routes today, 15 of which are considered “key” lines and operate with frequent service. Those key routes will likely go untouched, Hamwey said, because they are already filling a transportation need.

“There are corridors that are simply always going to be high priority bus corridors,” he said.

But Hamwey said the T could design new routes to connect parts of the region that have quickly grown in recent years. He expects the T to begin testing routes next year, and have a full plan for the new bus network by mid-2020 that could then be phased in.

The redesign could prove controversial in some corners, if the T ends up eliminating some low-ridership routes in outlying parts. Hamwey said candidates for elimination include routes where riders could be served by other regional transit agencies.

Meanwhile T board member Monica Tibbits-Nutt called on communities to work with the T as the redesign begins, especially by designating exclusive lanes on their roads for buses.

“You have to give something up if you want better bus service,” she said.

The new bus map may soon be followed by altogether new buses. Board member Brian Shortsleeve encouraged officials to think aggressively about replacing diesel buses with electric vehicles. The T will receive five new battery-powered buses next year that will be tested on the Silver Line, and in the future expects more of its fleet to be electric buses.

But MBTA chief engineer Erik Stoothoff said the agency is acting “cautiously aggressive” about the electric-vehicle technology, because it is quickly changing and still developing. In the meantime, the T is expected to purchase dozens of new hybrid electric-diesel vehicles later this year to replace some of its oldest diesel buses.