D2 Subway is a proposed 2.4 mi (3.9 km) expansion of the DART Light Rail system in metropolitan Dallas, Texas, in the United States. The subway would run from the existing Victory station, tunneling underground through the central business district of downtown Dallas, and connect to the existing tunnel under Cityplace. Four new stations would be built along the new alignment. The project is estimated to cost between $1.7 and $1.9 billion.