AlonPedestrian Observations: The United States Has Too Few Road Tunnels https://pedestrianobservations.com/2024/03/29/the-united-states-has-too-few-road-tunnels/
David M. Levinson ⁂@Alon NB: and of course Sydney loves road tunnels.
Cap'n Transit@Alon ugh, really?
@capntransit It's that or a bridge. When it's a new crossing, note that even with German tunneling costs and an enormous anti-Green backlash, the 17th section of A100 may not happen because it's a new road extension in a city that doesn't need them at a cost that isn't easy to fund.
@Alon Who says it's a tunnel or a bridge?
Garrett Wollman@Alon It seems likely to me that the Key Bridge will be replaced with another bridge with a somewhat broader main span, likely a different design.
@Alon (American highway engineers had, until recently, an unjustified aversion to cable-stayed bridges, which would be more resilient and easier to construct than a giant truss like the collapsed Key Bridge main span, but the public is also overly sentimental so I wouldn't be surprised to see them try to copy the old design but with piers farther removed from the edges of the shipping channel.)
@wollman (Why did American engineers dislike cable-stayed bridges?)
@Alon I do not know. It seems silly, considering how many were built in Europe during the immediate post-war reconstruction, but US engineers basically did not consider them until the 1980s. The Clark Bridge (1994, IL-MO) is the best known of the new cable-stayed bridges and the first really significant one; its construction was featured in a mid-90s NOVA episode, "Super Bridge". The Zakim Bridge in Boston was being designed about the same time.
OwenYou don't mention it in the article so I thought it would be worth highlighting...
Some advocates are pushing to have the I-5 replacement bridge into Portland turned into a tunnel project. I think they make a really strong case given the urban location and environmental impacts.
NYC Glue@Alon In Robert Caros 'The Power Broker' he ascribes Robert Moses saying he prefers bridges because they are visible. People don't see a tunnel.
Connor Crowley@Alon since the end of WW2 the only thing that has dictated tunnels in place of bridges has been access to naval yards for national defense purposes.
@Alon other thing I have noticed from an engineering capacity is the grades are significantly steeper in NL and pumping capacity appears to be lower (more frequent closers during rain.)
@ConnorC Yeah, @samth points out on Birdsite that the reason Hampton Roads has tunnels and not bridges is defense - bridges can be destroyed by enemy action and this would block access to the naval port. Same reason used to force the construction of the Brooklyn-Battery Tunnel when Moses preferred a bridge.
David Jaša@Alon the US also builds too few rail tunnels, especially those that would ease ruling gradient or total elevation gain (or loss).