The Chinese railway tunnels are divided into four classes by length: 1. * Super-long tunnels (over 10,000 metres) 2. * Long tunnels (between 3,000 and 10,000 metres) 3. * Middle tunnels (between 500 and 3,000 metres) 4. * Short tunnels (less than 500 metres) By 2008, there were 6,102 railway tunnels in operation in China. Their total length reached 3,938,913 metres (2,447.53 mi). This page lists the railway tunnels longer than 10 km (6 mi) in Mainland China, except those in metro systems.