Iranian dating siamak
Similar conclusions were reached for the 1971 Kingsway Tunnel under the Mersey.
In Hampton Roads, Virginia, tunnels were chosen over bridges for strategic considerations; in the event of damage, bridges would prevent US Navy vessels from leaving Naval Station Norfolk.
There are particular hazards with tunnels, especially from vehicle fires when combustion gases can asphyxiate users, as happened at the Gotthard Road Tunnel in Switzerland in 2001.
Secret tunnels are built for military purposes, or by civilians for smuggling of weapons, contraband, or people.
Special tunnels, such as wildlife crossings, are built to allow wildlife to cross human-made barriers safely.
However, navigational considerations may limit the use of high bridges or drawbridge spans intersecting with shipping channels, necessitating a tunnel.
Bridges usually require a larger footprint on each shore than tunnels.