If possible Elkhorno, could you draw the folowing? They will help me a lot with the modeling. I've gone through about four different versions of tunnel to dome connections and they all didn't look right when compared to the track and the tunnel itself.
-Tunnel Connection to Dome
-Road/Tunnel going through a urban block (Expressway style, off and above the city floor with some on and off ramps)
-Tunnel Door/Sealing Cap (assuming all tunnels can be opened, closed, or sealed off in case of colapse)
-A bit of the Underwater city Urban Sprawl Environs
Those are the few main ones I keep having problems envisioning and modeling. Your tunnels will be the main track and the tunnel Alandur did will be the side tunnels.