The Sydney Harbour Tunnel is a twin-tube road tunnel in Sydney, Australia. The tunnel was completed and opened to traffic in August 1992 to provide a second vehicular crossing of Sydney Harbour to alleviate congestion on the Sydney Harbour Bridge. It is one of two transportation tunnels under the harbour, the other being a set of rail tunnels for the Sydney Metro. The tunnel joins the Warringah Freeway at North Sydney and the Cahill Expressway at the entrance to the Domain Tunnel.