The most dense rail network in Europe of carries over 596 million passengers annually (as of 2015). In 2015, each Swiss resident travelled on average by rail, which makes them the keenest rail users. Virtually 100% of the network is electrified. The vast majority (60%) of the network is operated by the Swiss Federal Railways (SBB CFF FFS). Besides the second largest standard gauge railway company BLS AG two railways companies operating on narrow gauge networks are the Rhaetian Railway (RhB) in the southeastern canton of Graubünden, which includes some World Heritage lines, and the Matterhorn Gotthard Bahn (MGB), which co-operates together with RhB the Glacier Express between Zermatt and St. Moritz/Davos. On 31 May 2016 the world's longest and deepest railway tunnel and the first flat, low-level route through the Alps, the Gotthard Base Tunnel, opened as the largest part of the New Railway Link through the Alps (NRLA) project after 17 years of realization. It started its daily business for passenger transport on 11 December 2016 replacing the old, mountainous, scenic route over and through the St Gotthard Massif.