THE MBTA’S current plan for electrifying its commuter rail system calls for a hybrid approach using trains that draw power from overhead wires but also have the capability of running off batteries in tunnels, bridges, or on stretches of track where overhead wires are not feasible.

In a brief presentation to the MBTA board of directors, Alistair Sawers, head of rail transformation, acknowledged the rollout of electric trains and the maintenance facilities to support them will take until 2032, about the same time half of the existing diesel fleet will need to be replaced.

The previous MBTA oversight board passed a series of resolutions in 2019 pushing for an electrified regional rail network with trains operating every 15 minutes. The timing for the rollout was left vague, but the board pressed for pilot electric train projects quickly on the Fairmount and Providence/Stoughton lines and a portion of the Newburyport/Rockport line.

Sawers, who noted he was making his first appearance before a T oversight board in a year, said advocates have suggested the T isn’t moving fast enough, but he said he wanted to do more planning up front.

He said a technology review looked at the two extremes for electrification – trains running entirely off of overhead electric wires or trains relying on batteries – and came down in the middle.

 “We believe that the best solution is to mix the two,” he said.

The hybrid approach, Sawers said, should cost less and be installed much faster and installing wires on every line. He estimated it would take until 2063 to wire all 331 miles of the existing rail system and cost an enormous amount of money.

Sawers said the technology exists to combine batteries and off-wire power, but he said no transit system is doing it in the United States. He also said the T would not be one of the first rail systems to adopt the approach.

“We will not be buying something that’s straight bleeding edge off the shelf,” he said.

In the meantime, Sawers said, the T is looking at launching so-called urban rail routes that would provide quick 30-minute service on smaller trains between Boston and various prime destinations on several commuter rail lines.

Caitlin Allen-Connelly of the business group A Better City said she was concerned by the MBTA’s new approach on rail.

“We need more information before supporting such a radical shift away from the regional rail vision and approach approved by the Fiscal and Management Control Board in 2019,” she said in an email. “To meet the Commonwealth’s decarbonization goals, we need to offer commuter rail service that provides better frequency and time savings, more reliable service, and meets the needs of the region’s riders. The MBTA has already delayed the implementation of regional rail phase 1, and it is unclear from today’s presentation if the technology and approach proposed would achieve the benefits of a true regional rail system.”