Federal officials have approved an environmental study for a proposed 16-mile Purple Line in the Maryland suburbs, a milestone that allows the state to begin condemning private property for the light-rail line’s construction, Maryland officials said Thursday.

The approval, called a “record of decision,” also sets the clock ticking on potential lawsuits, which must be filed within 150 days.

The proposed light-rail line would run two-car trains mostly along local streets between Bethesda in Montgomery County and New Carrollton in Prince George’s County. It would have 21 stations and connect Maryland’s spokes of the Metrorail system.

President Obama’s fiscal 2015 budget recently recommended a federal commitment of $900 million toward the project’s estimated $2.37 billion construction costs. The next step will be continuing the line’s design and negotiating a long-term funding agreement with the Federal Transit Administration.

The Maryland Department of Transportation also is seeking bids from teams of private companies for a public-private partnership spanning 30 to 35 years to complete the design, help finance the line and then build, operate and maintain it. Those bids are due in the fall.

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