A new study has used satellite technology to identify at-risk bridges across the globe, highlighting particularly poor conditions in North America. Researchers analyzed 744 long-span bridges and found that integrating radar data could reduce high-risk classifications by about one third. This approach promises better monitoring, especially in regions with limited resources.
Scientists have developed a method using satellites to monitor bridge stability and detect early signs of structural issues. Published in Nature Communications in 2025, the study by Pietro Milillo from the University of Houston and collaborators examined 744 long-span bridges worldwide. It revealed that North American bridges are in the poorest condition, followed by those in Africa, with many in North America built during the 1960s and now approaching or exceeding their design life.
The team employed Multi-Temporal Interferometric Synthetic Aperture Radar (MT-InSAR), a remote sensing technique that measures millimeter-scale movements in structures. This complements traditional visual inspections, which occur only twice a year and can be costly and subjective. Structural Health Monitoring (SHM) sensors, while more continuous, are installed on fewer than 20% of the world's long-span bridges.
Incorporating MT-InSAR data into risk assessments could lower the number of high-risk bridges by about one third. Among those still classified as high-risk, roughly half could benefit from ongoing satellite observations. The greatest potential lies in areas like Africa and Oceania, where monitoring is currently limited.
"Our research shows that spaceborne radar monitoring could provide regular oversight for more than 60 percent of the world's long-span bridges," said Milillo, an associate professor of civil and environmental engineering at the University of Houston. "By integrating satellite data into risk frameworks, we can significantly lower the number of bridges classified as high-risk, especially in regions where installing traditional sensors is too costly."
Co-author Dominika Malinowska from Delft University of Technology and the University of Bath noted, "While using MT-InSAR to monitor bridges is well-established in academic circles, it has yet to be routinely adopted by the authorities and engineers responsible for them. Our work provides the global-scale evidence showing this is a viable and effective tool that can be deployed now."
The method uses data from satellites like the European Space Agency's Sentinel-1 and NASA's NISAR mission, combined with SHM sensors, to offer more frequent updates on bridge conditions and improve maintenance decisions.
