The 21-station line will run inside the Capital Beltway from Bethesda in the east to New Carrollton in the west, with direct connections to Metrorail's Orange Line, Green Line and two branches of the Red Line and to the Marc commuter rail Brunswick, Camden and Penn lines.

The $US 2.37bn project is being implemented as a Public Private Partnership (PPP) by Maryland Transit Administration (MTA). With FTA approval, MTA can now proceed with final design and land acquisition, and the state of Maryland has already allocated $US 280m for this purpose. The decision will also allow MTA to begin discussions with FTA to secure a full funding grant agreement (FFGA) from the federal government.