Not just that. You need telematics (you don't want cars stuck in the tunnel - if a fire breaks out, it's a death trap), you need emergency exit/access tunnels,

Not just that. You need telematics (you don't want cars stuck in the tunnel - if a fire breaks out, it's a death trap), you need emergency exit/access tunnels, you need ventilation tunnels, and you need all of that to run in HA mode. "Just a hole in the ground" is a very simplistic view; but perhaps this is a thought-provoking way to put it, EM is known for some radical solutions.