This week marks one year since the Francis Scott Key Bridge collapsed after it was hit by the Dali, a container ship. When the bridge fell, six construction workers died, the channel to the Port of Baltimore was blocked for over 10 weeks, and the region lost a major commercial thoroughfare.

In February, the state of Maryland released the design for a new bridge that will go where the Key Bridge stood. The design is still in its early stages, but the new bridge has an expected life span of 100 years. That means this bridge will have to accommodate not just the ships and trucks of today, but those a century from now. 

One change to the new bridge? It’s going to look different from the old one.

“The old Key Bridge was truss, a kind of design that looks like, kind of a cage, and that is holding up the roadway,” said Rick Geddes, who studies infrastructure policy as a professor at Cornell University.

Geddes said truss bridges were very common back in the 1970s, when the old Key Bridge was built. The new bridge will be a kind Geddes said is more commonly built now — what’s called a “cable-stayed bridge.” 

“You have very tall towers, and those towers hold cables, and the roadway is suspended under the towers via those cables,” said Geddes. “And so the cable-stayed design allows the center span to be longer.”

The center, or main span, of the bridge goes over the shipping channel. The old Key Bridge’s main span was about 1,200 feet. The new one is expected to be at least 1,600.

“So the likelihood that a big ship is going to veer out of the channel and hit a part of the bridge is reduced by the fact that you have towers much — about a third, which is a lot — wider apart than under the old bridge,” said Geddes.

The deck of the new bridge, where the road is, will also be about 45 feet higher than the old one. That could allow bigger ships to pass underneath.

“Today, right now, there are certain cruise ships that cannot serve the Port of Baltimore, because they’ve gotten very large,” said Paul Wiedefeld, secretary of Maryland’s Department of Transportation, which is overseeing the project.

Will the new bridge accommodate the biggest ships?

“Mmmm, probably not the biggest in the future,” he said. “I mean, you have to think of it in this scale, the Port of Baltimore versus other ports.”

Wiedefeld said the Port of Baltimore does have plenty of room to grow, but there are some geographical limits. 

“You know, it’s tight. It’s within a very dense urban environment,” he said.

But, as with other kinds of infrastructure, there have been big advances in bridge-building technology in the last half century.

“You’re building a bridge for 100 years, so you start to use materials that can last much longer,” said Wiedefeld. 

For example, there are better coatings for metal that protect against corrosion, said civil engineer Maria Lehman, who recently worked on a different bridge designed to last at least 100 years — the Governor Mario M. Cuomo Bridge over the Hudson River in New York, which opened in 2018.

Also, she pointed out, you can now embed sensors in a bridge that will give a heads up when something is off.

“You get an alarm, ‘Hey, you should check this out.’ Things that normally you may not notice with a visual inspection, because it’s going on at the steel level,” said Lehman.

Lehman said from an engineering standpoint, you can address a lot of different outcomes — but you’re on a budget.

“You really have to think about risk, which is the probability of failure times the consequences of the failure,” said Lehman. “And where is that sweet spot, where you’re investing enough that you’re meeting the risk, but not too much, because there isn’t an unlimited pot of money to be able to do this.”

In the case of the new bridge in Baltimore, there’s also not unlimited time. Maryland’s goal for opening the new bridge is Oct. 15, 2028. 

And forecasting what shipping and trucking will look like in 2128 is hard, said Ben Schafer, who studies civil and systems engineering at Johns Hopkins University.

“If there’s another new idea that you and I can’t really even conceptualize right now, and that becomes the most important way to move goods around, there’s not an easy way to get into that sort of prediction,” said Schafer.

The best engineers and planners can do is rely on current standards. One of the groups that works to develop these standards is the American Association of State Highway and Transportation Officials, or AASHTO.

“We take the data and the information that’s available to us, the research that’s available to us, and we do the best that we can to project forward as to what may be occurring into the future,” said Kevin Marshia, the director of engineering for AASHTO.

Basically, trying to take into account how commerce may change in the years to come.