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

> 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...

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.