The WMATA (Washington Metropolitan Area Transit Authority) Metrorail System is the second busiest rapid transit system in the U.S. and includes 6 lines with more than 117 route-miles of track and 91 passenger stations. The trains are powered by more than 100 traction-power substations across the network through a third-rail 700 V dc distribution system. This system consumes about 500,000 MWh per year, at a cost of approximately $48 million.