The Madrid Metro is a metro system serving the city of Madrid, capital of Spain. The system is the 8th longest metro in the world, though Madrid is approximately the fiftieth most populous metropolitan area in the world. Its fast growth in the last 20 years has also put it among the fastest growing networks in the world, rivalling many Asian metros such as the Shanghai Metro Guangzhou Metro, Beijing Subway, and Delhi Metro.
Unlike normal Spanish road and rail traffic, which uses right hand drive, Madrid Metro trains use left-hand running on all lines because traffic in Madrid drove on the left until 1924, well after the Madrid Metro started operation. The Madrid Metro operates every day from 6 am until 1:30 am. A light rail system feeding the metro opened in 2007 called Metro Ligero (light metro). The 'Cercanias' system works in conjunction with the metro servicing commuter train services to and across the city.