The Italian railway system is one of the most important parts of the infrastructure of Italy, with a total length of of which active lines are 16,723 km. The network has recently grown with the construction of the new high-speed rail network. Italy is a member of the International Union of Railways (UIC). The UIC Country Code for Italy is 83. The network RFI (Rete Ferroviaria Italiana, Italian Rail Network), a state owned infrastructure manager which administers most of the Italian rail infrastructure. The total length of RFI active lines is , of which are double tracks. Lines are divided into 3 categories: fundamental lines (fondamentali), which have high traffic and good infrastructure quality, comprise all the main lines between major cities throughout the country. Fundamental lines are long; complementary lines (complementari), which have less traffic and are responsible for connecting medium or small regional centers. Most of these lines are single track and some are not electrified; node lines (di nodo), which link complementary and fundamental lines near metropolitan areas for a total . Most of the Italian network is electrified (). Electric system is 3 kV DC on conventional lines and 25 kV AC on high-speed lines. The Italian rail network comprises also other minor regional lines controlled by other companies, such as Ferrovie Emilia Romagna and Ferrovie del Sud Est, for a total of History The first railway in Italy was the Napoli-Portici line, built in 1839 to connect the royal palace of Naples to the seaside. After the creation of the Kingdom of Italy in 1861, a project was started to build a network from the Alps to Sicily, in order to connect the country. The first high-speed train was the Italian ETR 200, which in July 1939 went from Milan to Florence at , with a top speed of . With this service, the railway was able to compete with the upcoming airplanes. The Second World War stopped these services. After the Second World War, Italy started to repair the damaged railways, and built nearly of new tracks. Nowadays the rail tracks and infrastructure are managed by Rete Ferroviaria Italiana (RFI), while the train and the passenger section is managed mostly by Trenitalia. Both are Ferrovie dello Stato (FS) subsidiaries, once the only train operator in Italy. High-speed rail High-speed trains were developed during the 1960s. E444 locomotives were the first standard locomotives capable of