page_title: North Downs Tunnel
hierarchical_section_title: North Downs Tunnel
caption_attribution_description: Still a lot of dust was present in North Downs tunnel
context_page_description: The North Downs Tunnel, also known as the Blue Bell Hill Tunnel, is a railway tunnel that carries High Speed 1 through the North Downs, at Blue Bell Hill near Maidstone in Kent, south-east England.
  The tunnel is 3.2 kilometres long, with an internal diameter of 12 metres and a cross-sectional area of 150 square metres, and descends to a depth of 100 m below the chalk hills. Thus, at the time of its completion, the North Downs Tunnel was both the largest and deepest twin-track railway tunnels to have ever been constructed in the UK. Trains using High Speed 1 are able to attain speeds of up to 300 kilometres per hour whilst in the tunnel.
context_section_description: The North Downs Tunnel, also known as the Blue Bell Hill Tunnel, is a railway tunnel that carries High Speed 1 through the North Downs, at Blue Bell Hill near Maidstone in Kent, south-east England.
  The tunnel is 3.2 kilometres (2 mi) long, with an internal diameter of 12 metres (40 ft) and a cross-sectional area (CSA) of 150 square metres, and descends to a depth of 100 m (325 ft) below the chalk hills. Thus, at the time of its completion, the North Downs Tunnel was both the largest (in terms of CSA) and deepest twin-track railway tunnels to have ever been constructed in the UK. Trains using High Speed 1 are able to attain speeds of up to 300 kilometres per hour (186 mph) whilst in the tunnel.
caption: North portal, dust whipped up by a test train before opening in 2003
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