Scientists are using satellites to reveal which bridges around the world are at risk of collapse and how to spot problems before disaster occurs.
- Adding satellite monitoring to bridge inspections reduces the number of structures labeled as high-risk by about a third.
- About half of the bridges that are still ranked as high risk could benefit from continued observations from space.
- The greatest impact may be achieved in regions such as Africa and Oceania, where bridge monitoring is currently limited or almost non-existent.
University of Houston researchers are helping identify weak bridges around the planet and offering new ways to address potential failures before they become catastrophic.
In a global analysis of 744 bridges published in nature communicationsPietro Milillo and collaborators from several international organizations assessed the condition of bridges around the world. They found that bridges in North America were generally in the worst condition, followed by bridges in Africa. The team also proposed a strategy that could transform the way infrastructure is monitored around the world by using satellites to track bridge stability and detect warning signs early.
Aging infrastructure and growing risks
Many of the bridges identified in the study are nearing the end of their planned service life. North America saw a surge in bridge construction in the 1960s. This means that many of these structures are now decades old and approaching or exceeding their original design lifespan.
To address this challenge, researchers are turning to space-based surveillance systems that utilize synthetic aperture radar. This technology frequently captures high-resolution images, covering large areas of the globe, while also providing access to extensive historical data.
“Our study shows that more than 60% of the world’s long bridges could be regularly monitored with space-borne radar monitoring,” said Milillo, co-author of the study and associate professor of civil and environmental engineering at the University of California. “By integrating satellite data into a risk framework, we can significantly reduce the number of bridges classified as high risk, especially in areas where installing traditional sensors would be too costly.”
Detect small movements from space
The international research team included Dominika Malinowska from Delft University of Technology (TU Delft) and the University of Bath, Cormac Reale and Chris Blenkinsopp from the University of Bath, and Giorgia Giardina from TU Delft. They relied on a remote sensing method known as multi-temporal interferometric synthetic aperture radar (MT-InSAR).
This technology can complement traditional inspections by identifying very small changes in structure. The system can measure movements as small as a few millimeters caused by slow geological processes such as landslides and land subsidence. It may also reveal widespread unusual patterns that may indicate new structural problems.
Bridges are some of the most fragile components of transportation systems, but current approaches used to monitor bridges have clear limitations. In-person visual inspections can be costly and sometimes subjective. Additionally, because inspections are typically only performed twice a year, early warning signs of deterioration may go unnoticed between inspections.
Structural Health Monitoring (SHM) sensors provide a more continuous way to track structural performance. However, these systems are typically only installed on new bridges and structures that are already known to have problems. According to the study, less than 20% of the world’s long bridges are equipped with these sensors, leaving many structures without consistent monitoring.
Satellite-based surveillance solution
“Remote sensing can complement SHM sensors, reduce maintenance costs, and support visual inspection, especially when direct access to a structure is difficult,” Millilo said. “For bridges in particular, MT-InSAR enables more frequent deformation measurements across the entire infrastructure network, unlike traditional inspections that are typically performed only a few times a year and require personnel on the ground.”
Malinowska said. “While the use of MT-InSAR for bridge monitoring is well-established in academia, it has not yet been routinely adopted by authorities and engineers responsible for bridges. Our study provides global evidence that this is a viable and effective tool that can be deployed now.”
Researchers found that adding MT-InSAR data to bridging risk assessment improved accuracy. This technique analyzes satellite pixels known as persistent scatterers (PS) that have stable radar returns. These signals reduce uncertainty and allow engineers to better prioritize which bridges require maintenance or further inspection.
The approach proposed by the researchers combines monitoring information from SHM sensors with satellite observations from systems such as the European Space Agency’s Sentinel 1 and NASA’s recently launched NISAR mission. Integrating these data sources into a bridge’s structural vulnerability score allows engineers to receive updates more frequently than traditional inspection schedules.
More consistent monitoring will give authorities a clearer picture of bridge conditions and help them make better decisions about maintenance and risk management.
