The federal government has approved Baltimore’s Red Line light rail project for more detailed engineering, and Maryland officials said Tuesday that they expect a Purple Line in the Washington suburbs will receive similar permission later this summer.

The Federal Transit Administration has approved a proposed 14.5-mile Red Line for further engineering to fine-tune cost estimates and construction schedules and to finalize environmental studies, state officials said. The line is estimated to cost $2.2 billion. If it receives federal construction money, state officials say, it would open in 2020.

Maryland transit officials have said a 16-mile light rail Purple Line between Bethesda and New Carrollton will follow a similar engineering and construction schedule as a Red Line. A Purple Line is estimated to cost $1.93 billion to build and require $18 million in local operating subsidies annually. A Corridor Cities Transitway proposed for the Interstate 270 corridor in upper Montgomery County also is in the planning stages.

The federal government grants state transit planners permission to proceed from one stage of planning and design to the next as part of a multi-year “New Starts” competition for federal construction money.