Major work on Tobin Bridge to start in 2018

The project calls for the Tobin Bridge’s lower deck, which carries northbound lanes, to be repaired. The upper deck will be repaved. –David L Ryan/Globe Staff/file

State transportation officials approved a plan Monday to rehabilitate a major stretch of the Tobin Bridge into Chelsea, a project that is expected to cause lane closures and traffic disruptions into 2020.

The $41.6 million project, approved by the board of directors for the Massachusetts Department of Transportation, is scheduled to start in April and will take place from spring to fall each of the next three years.

The Tobin Bridge, opened in 1950, carries Route 1 over the Mystic River between Charlestown and Chelsea. The upcoming work will focus on a 1,675-foot stretch where cars approach Chelsea after passing the bridge’s iconic green truss structure, potentially affecting tens of thousands of motorists who cross the bridge each day.