Union square

Emergency drill planned for the Green Line between Lechmere and Union Square

Transit workers and firefighters will conduct an emergency response drill involving a staged train derailment between the newly constructed Lechmere and Union Square stations on Sunday morning, the Massachusetts Bay Transportation Authority said in a statement.

The exercise is scheduled to take place between 10 a.m. and noon, with teams arriving as early as 7 a.m. in the area being constructed as part of the Green Line Extension Project, according to the MBTA statement.

Green Line service will not be affected by the exercise, the MBTA said.

The emergency scenario will involve an outgoing train exceeding the speed limit between Lechmere and Union Square. The MBTA said it would hit a train ahead of it and derail before coming to a complete stop.

Workers will assist several passengers who will act as if they have been injured, while other passengers will evacuate from the train, the statement said.

“The exercise is designed to establish a learning environment for public safety officials to practice emergency response plans, policies and procedures in relation to a mass casualty event on a train of the Green Line on a new section of the viaduct,” the MBTA said in the statement.

Representatives from multiple agencies have planned the drill and will participate in it on Sunday, including Transit Police, MBTA Operations and the Cambridge, Somerville and Medford Fire Departments, the MBTA said.

Caroline Enos can be reached at [email protected]. Follow her on Twitter @CarolineEnos.