MBTA riders and motorists can expect some detours and traffic jams throughout the areas served by the MBTA's Green Line next year as the T makes upgrades to the trolley line's road crossings.

MBTA managers told the agency's board Monday they plan to spend $15 million on work between April 2018 and April 2019 to replace 27 road grade crossings where the Green Line trolleys cross over Huntington Avenue, Beacon Street, Commonwealth Avenue and other busy Boston streets.

T managers expect to spend another $15 million for a second phase of the project after 2019.

T infrastructure chief Erik Stoothoff presented options to the board for even more work in the coming years for replacing track and rails on much of the Green Line, meaning service shutdowns and shuttle buses for riders while the crucial repairs are made.

"It is not focused on the idealization of alignments or changing the geometry of the Green Line itself, it's focused strictly on the Green Line that we have today and making that system as best as we can," Stoothoff said.

General Manager Luis Ramirez says the work is a critical part of the plan to complete the T's $7 billion in deferred maintenance.

The MBTA authorized contracts for the construction of the Green Line extension project and for the overhaul of the Charlie Card fare system at last week's meeting of the Fiscal and Management Control Board. At Monday's meeting, board members received updates on vehicle maintenance programs for the Orange, Red and Blue subway lines and heard public opposition to plans to outsource the labor at some bus maintenance facilities.

The board also heard an update on new housing and retail developments near the Quincy Center Red Line station, part of the major renovation of Quincy's downtown.