Bridge/Tunnel Metros (authority, port authority, MBA)

[mhays25]

The Seattle MSA has dual suspension bridges at the Tacoma Narrows (no collapses in decades!).

We have one under-water tunnel (not underwater per se), the Link Light Rail tunnel under Montlake.

We also have numerous other rail and highway tunnels, both through hills and to get out of the way in flatter areas.

[PortCity]

Mobile, Al has both bridges and tunnels.

[pnwguy2]

Originally Posted by mhays25

The Seattle MSA has dual suspension bridges at the Tacoma Narrows (no collapses in decades!).

We have one under-water tunnel (not underwater per se), the Link Light Rail tunnel under Montlake.

We also have numerous other rail and highway tunnels, both through hills and to get out of the way in flatter areas.

And don’t forget the three floating bridges in Western Washington. Two in Seattle and one in Kitsap County across the Hood Canal.

[mhays25]

We have countless bridges of many types...high ones, drawbridges, floating bridges, locks where throngs of tourists walk across the movable gates....

[Tusco]

All states with tunnels are highlighted in blue

[bus man]

For underwater automobile tunnels, I can't think of a single metro that comes close to the Hampton Roads area. (Not sure if the residents there refer to their metro as "Hampton Roads" or "the Norfolk area" or "Tidewater" or what.) New York and Baltimore have two each, which isn't too shabby.

EDIT: New York has more than that. For some reason I was thinking only of tunnels under the Hudson River. My bad.

[pnwguy2]

Also forgot to mention the I-90 Seattle tunnel combines with the I-90 floating bridge. It is really an amazing double experience. Both east and westbound. There may be others like this but this one may be the best.

[Guineas]

Originally Posted by mhays25

The Seattle MSA has dual suspension bridges at the Tacoma Narrows (no collapses in decades!).

We have one under-water tunnel (not underwater per se), the Link Light Rail tunnel under Montlake.

We also have numerous other rail and highway tunnels, both through hills and to get out of the way in flatter areas.

Seattle area has several floating bridges. The water is too deep and the span too long for suspension bridges. 520 across Lake Washington with views of Mount Rainier in one direction and the Olympics in the other direction right over the water is pretty impressive. You don't have much bridge infrastructure blocking your views either.

The Highway 99 tunnel goes under the downtown area.

There are also tons of drawbridges across the city.

[pnwguy2]

There have been proposals for bridges across Puget Sound north of Tacoma Narrows for decades. While the technology is doable it would be expensive. I would guess the ferry fans are against it too. That said, it all falls under WSDOT.
So economically the point is moot. Build a bridge and decrease the ferries? I’m sure this has been studied economically, but for now the current ferry system is strongly in place. Will it eventually change? Yes, like everything does. (See SF/Oakland ferry service history).

[mhays25]

That would cost many billions. I've never heard of any major support. Not going to happen in the foreseeable future.