The Cross-Harbour Tunnel (abbreviated CHT or XHT) is the first tunnel in Hong Kong built underwater. It is two steel road tunnels each with two lanes constructed using the single shell immersed tube method.
It is the earliest of three vehicular harbour crossings in Hong Kong, opened for traffic on 2 August 1972. It was constructed under 30-year private-sector franchise based on a build–operate–transfer model, and title passed to the Hong Kong government in August 1999 upon termination of the franchise. It has become one of the most congested roads (mainly towards the Hong Kong Island direction) in Hong Kong and the world.
Constructed by a private company and operated under a 30-year franchise, the 1.8 km (1.1 mi)-long tunnel crossing opened in 1972, providing the first road link between Kowloon and Hong Kong Island. Prior to the opening of the tunnel, cross-harbour vehicular traffic depended on ferries and for passengers, the Star Ferry.
It was administered by The Cross-Harbour Tunnel Company Ltd until August 1999, when the operation franchise agreement expired and the government assumed control. Since 1 November 2010, the tunnel is managed, operated and maintained by Serco Group on contract basis.