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Comment by mcv | Hacker News Reader

If it's a very major port, they can afford to make it a tunnel.

Tunnels are far more expensive - the 1.5 mile 4 lane Fort McHenry tunnel was like $750M vs. $140M for the 1.6 mile 4 lane Key bridge, although adjusted for inflation that’s probably more like $750M vs $320M.

The underlying problem here is that automobiles are inherently inefficient so you either get epic traffic jams or have to massively overbuild capacity, forcing the engineers to deliver as many lanes as they can for the budget.

How expensive is this accident to the city? Likely billions, right?

Your point is correct: if they knew the accident was going to happen today, they might have changed their behavior.

Unfortunately, nobody who knew it would happen today warned anybody.

Yes, but there’s a difference between what people will pay in advance to prevent one of many low probability catastrophic failures and what they’ll think was worthwhile for someone else to have paid to prevent the one which actually happened.

Those calculations are really hard: say they had built a tunnel, what are the odds of the same number of people dying in a fire after someone crashes into another car? Would we have needed to spend any money at all if more people had used railroad alternatives to driving and such an expensive bridge or tunnel was not justified on traffic grounds?

This works fine until there's a story of issues with a tunnel, then we say we should have built a bridge.

There already are two tunnels for I-95 and I-895 under the port.

Then why is this one a bridge? Why not go all the way and make this a tunnel too?

Mostly to have a hazmat route around the city (HAZMAT trucks aren’t allowed in the tunnels) and because bridges are cheaper than tunnels. They needed a third crossing because the traffic warranted it.

> Mostly to have a hazmat route around the city (HAZMAT trucks aren’t allowed in the tunnels)

That is a very interesting point I hadn't considered at all. Price is an obvious point, but I hadn't considered hazmat.

It does make me wonder how hazmat traffic is handled around Amsterdam. I think they are allowed in some tunnels here.

Most highway tunnels (including the Coentunnel and Zeeburgertunnel on the A10 ring road around Amsterdam) are category C tunnels, which means some hazmat allowed depending on the nature of the materials, the quality of the containment, and the volume transported. Notable exceptions are the Schipholtunnel (category A, fewer restrictions) near the airport and the Arenatunnel (category E, severely restricted) under the stadium.

HAZMAT can go the other way around the city on 695. My understanding is that the main issue was cost.

> Bids for construction of the proposed Outer Harbor Tunnel were opened in July 1970, but price proposals were substantially higher than the engineering estimates.[11] Officials drafted alternative plans, including a four-lane bridge, which was approved by the General Assembly in April 1971.[12][13]

https://en.wikipedia.org/wiki/Francis_Scott_Key_Bridge_(Balt...

Why does anyone use fragile asphalt (20 years) for busy roads when engineered concrete lasts 50 or more? Because the better option costs more.

This was a big point of contention when a local town announced it was replacing the failing asphalt on the section with the most traffic with slabs of concrete. [0] People complained about the price. Meanwhile, over a decade on, nearby asphalt laid with the same renewal project is already cracking while the busy main thoroughfare remains undisrupted by road work.

It's hard to persuade people that long-term investment is worthwhile.

[0] PDF page 10 (print 17): https://www.dot.ga.gov/PartnerSmart/Public/Documents/publica...

The tunnel and the bridge run parallel. Tunnels are not suitable for all types of traffic.

However hazardous cargo is not allowed in tunnels so bridges like this one are the only way hazmat can be transported over water crossings.

On the news this morning a commentator made it sound like that rule was imposed after 9/11.

It makes sense to me that cargo would be restricted, and it's bizarre that it would be related to terrorism (an additional rule isn't going to prevent an attack...).

It's still a sensible rule. As we see with this incident rare events do happen.

In addition to the Hazmat issue mentioned below, tunnels have a bad record when fires break out inside them. E.g. the Kaprun disaster [0] which killed 150 people, and the Gotthard Road Tunnel [1] fire, after which the use of large vehicles was constrained.

[0] https://en.wikipedia.org/wiki/Kaprun_disaster

[1] https://en.wikipedia.org/wiki/Gotthard_Road_Tunnel#2001_coll...

The Patapsco is much wider here than at the locations of the two tunnels. It would have been a much bigger and more expensive project to build a tunnel that long.

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