Transport in Spain is characterised by an extensive network of roads, railways (including the world's second longest high speed rail network), rapid transit, air routes, and ports. Its geographic location makes it an important link between Europe, Africa, and the Americas. Major forms of transit generally radiate from the capital, Madrid, located in the centre of the country, to link with the capitals of the autonomous communities. Spanish transit is marked by a high degree of integration between its long-distance railway system and inner-city metro systems, although the historic use of broad gauge has limited integration with its neighbours. Spain is currently working to increase and improve linkage with the rail systems of France and Portugal, including the high-speed rail line between Madrid and Lisbon. Spain's highway system is highly developed, with both tolled and free motorways. Air traffic is routed through several international and regional airports, the largest of which is Barajas International Airport in Madrid. Rail transport and AVE transport Spanish railways date from 1848. The total route length in 2017 was 15,333 km, of which 9,699 km were electrified. Four different track gauges are used in Spain. Iberian gauge (): 11,333 km (6,538 km electrified at 3 kV DC) Standard gauge (): 2,571 km (all electrified at 25 kV AC) Narrow gauge (): 1,207 km (400 km electrified) Narrow gauge (): 28 km (all electrified) Most railways are operated by Renfe; narrow gauge lines are operated by FEVE and other carriers in individual autonomous communities. It is proposed to build or convert more standard gauge lines, including some dual gauging of broad gauge lines, especially where these lines link to adjacent countries. A high-speed rail line (AVE) between Madrid and Seville was completed in 1992. In 2003, high-speed service was inaugurated on a new line from Madrid to Lleida and extended to Barcelona in 2008. The same year, lines from Madrid to Valladolid and from Córdoba to Málaga were inaugurated. In 2010, AVE line Madrid-Cuenca-Valencia was inaugurated. Cities with metro/light rail systems Alicante - Alicante Tram Barcelona - Barcelona Metro & Tram Bilbao - Bilbao Metro & Bilbao tram (Euskotren Tranbia) Castellon - Trolleybus A Coruña - under construction Granada - Granada Metro Jaén - Jaén Tram - completed but not operated Madrid - Madrid Metro Málaga - Málaga Metro Murcia - Murcia tram Palma - Palma Metro Parla - Parla Tram Santa Cruz de Tenerife -