A consultant will complete a new study of the Red-Blue Connector by fall 2020, outlining what the current cost would be for a long-sought project to connect two of the MBTA’s main subway lines in downtown Boston.

Boston firm AECOM was tapped as the MBTA renews its exploration of the potential connection. Over the next 10 to 12 months, the consultant will review past studies and environmental impact assessments conducted about the feasibility of the project to “refresh” understandings and cost estimates, according to MBTA Chief Engineer Erik Stoothoff.

“This is a very early update,” Stoothoff told the MBTA’s Fiscal and Management Control Board on Monday. “We have just engaged this consultant to help us with this engineering evaluation.”

An MBTA spokesman could not immediately provide an estimate of what AECOM will be paid for its consulting work.

The link between the Red and Blue Lines has been floated for years and was agreed to as environmental mitigation for the Big Dig construction project, but the design process ran out of momentum. This year, officials revived interest in the connector, including a rail link as a long-term priority in the MBTA’s plans for development by 2040. However, transit activists and business leaders say the project can and should be done much more quickly to help reduce traffic, particularly trips between Kendall Square and Logan Airport.