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With extreme heat, we can’t build roads and railways as we used to

Buckled roads, warped train tracks and expanded bridges are a stark reminder, experts say, of the need to adapt quickly to a warming planet

Water is sprayed on the taxiways at the Schiphol airport in Amsterdam to prevent the deformation of the asphalt, due to a heat wave in July 2019. (Robin van Lonkhuijsen/AFP/Getty Images)

Roads and airport runways buckling. Train tracks warping. Bridges swelling.

These are just some of the damaging effects extreme heat has had on critical infrastructure in recent years, as heat waves have become more frequent and intense — a stark reminder, experts say, of the need to adjust quickly to a warming planet.

“Most of our physical infrastructure was built using the temperature records of the mid-20th century,” Costa Samaras, principal assistant director for energy with the White House’s Office of Science and Technology Policy, wrote in an email. “That is not the climate we have now.”

Samaras added: “Melting roads and runways are no longer a hypothetical — and we know with increased emissions it’s only going to get hotter.”

The latest scramble to adapt came this week as heat waves smothered parts of the United States and Europe, sending temperatures in many historically temperate areas skyrocketing. In London, for instance, parts of a Victorian-era bridge were wrapped in silver insulation foil to protect the metal from cracking. Meanwhile, steel train tracks warped and buckled, and airport runways were damaged by the heat, causing widespread travel disruptions.

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“When reality and future conditions start shifting away from what was used in the design, our infrastructure becomes more prone to failure and may also suffer from a reduced service life,” Amit Bhasin, a professor and director of the Center for Transportation Research at the University of Texas at Austin, wrote in an email.

But experts stressed that solutions should not focus solely on improving infrastructure. “The bottom line is: we are not going to only build our way out of this,” Samaras said. “We must decarbonize our energy uses and learn how to remove carbon we’ve already added to the atmosphere.”

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What infrastructure is at risk?

Heat can impact all types of physical infrastructure, but roads, runways and railways may be among the most vulnerable, said Ladd Keith, an assistant professor of planning and chair of sustainable built environments at the University of Arizona’s College of Architecture, Planning and Landscape Architecture.

Paved surfaces, such as roads and runways, are typically made of asphalt or concrete, materials that can be affected, in some cases dramatically and quickly, by heat.

“Asphalt is a temperature-sensitive material, so when it gets hot, it gets really soft,” said Jo Sias, a professor of civil and environmental engineering at the University of New Hampshire.

While many descriptions of extreme heat’s effect on asphalt include the word “melting,” that isn’t entirely accurate, said Steve Muench, a professor of civil and environmental engineering at the University of Washington. Instead, he said, the effect is more similar to what you could do to Play-Doh or clay.

Asphalt also tends to age faster at higher temperatures, which can reduce its life span, Bhasin said.

For roadways that use concrete, expansion caused by unusually hot weather can be a major problem. These thoroughfares are paved with slabs and designed with space in between to account for expansion (when it’s hot) or contraction (when it’s cold), Muench said. But when temperatures are much higher than usual and if improper maintenance has lead to debris getting into the spaces, the slabs can run out of room to expand, eventually causing “concrete pavement blowups or buckling,” he said.

Expanding is also an issue for the steel used to construct train tracks, Sias said. “All of a sudden, the individual rails, they don’t have enough room to expand, so they’ll just buckle. Then, you get those curves in the railway lines, which obviously are not good.”

What is the tipping point?

The answer often depends on location and design. “There may not always be a magic number at which the infrastructure will go from ‘working’ to ‘failed,’” Bhasin said.

Physical infrastructure is traditionally designed based on the historical conditions of a particular location, Keith said. That means the point at which extreme heat starts to affect surfaces varies depending on the past climate of that location.

“Any kind of prolonged extreme heat outside of that past climate will push the physical infrastructure into dangerous territory,” he said.

What can be done?

It’s important to be prepared to make immediate repairs, Sias said. Public agencies should know that extreme weather can cause damage and have the supplies on hand to react promptly.

“In terms of predicting where things like buckling are going to happen, it’s very, very difficult to do,” she said. “There’s no real models or anything that will tell you, ‘Okay, this joint is going to buckle, but this one’s not.’ ”

Still, there are some “relatively mundane engineering things” that can be done to lower the chances of negative impacts, Muench said.

For example, concrete slabs used for road pavement can be made smaller. “The shorter the slab is, the less length change it undergoes during heating and cooling,” he said. “If you can reduce that length change, then the likelihood of something like a blowup would be less.”

Modifications can also be made to an asphalt mixture that makes it stiffer in higher temperatures and more resistant to cracking at lower temperatures, he said.

It may also be helpful to plant trees along roadways to create shade, or to use “cool pavement,” which is in lighter colors and slightly more reflective than what is traditionally used, Keith said.

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But he and other experts emphasized that broader changes and, in particular, efforts to adjust infrastructure design, are critical for adapting to future extreme weather.

A 2017 study that assessed extreme climate impacts on infrastructure in Europe noted that heat waves would account for about 92 percent of total hazard damage in the transport sector by the 2080s, with much of the effects expected on roads and railways.

“We need to think longer term and more holistically about heat,” Keith said. “We need to make sure that every time that we have a roadway project or a railway project of the future, that we’re making sure to design it for the climate that we’re pushing ourselves into and not the one that we’re currently in or the one that we’ve had been in the past.”

A holistic approach, Bhasin added, should also include taking steps to understand and mitigate the causes for these extreme temperature events.

“If not, we may continue in a downward spiral,” he said.