2. The question is whether the tunnel can provide for this volume of traffic. An eight-lane tunnel would have to be very wide or it will need two tunnels. Even if it is a double-decker like the Smart Tunnel in Kuala Lumpur, it needs to be very tall especially as it must cater for the heavy vehicles with their containers etc.
3. Because it will be far below the sea-bed it will have to begin and end far inland as lorries and trucks need gentle gradients. It can be as far as four kilometres for both ends. This, together with the undersea part will stretch the tunnel to almost eight kilometres.