06/01/2026
What happens when you run a train across a bridge that floats? 🚄
The I-90 Homer M. Hadley Memorial Bridge is one of the longest floating bridges in the world. Now it also carries Sound Transit's 2 Line light rail, creating a unique challenge: cars can handle small bumps and bridge joints, but train tracks need to stay smooth and precisely aligned.
To monitor the bridge in real time, University of Washington Civil & Environmental Engineering researchers built a digital replica that pulls in sensor data on weather, GPS positioning, anchor cable tension and more, allowing maintenance teams to view a 3D model and see current conditions across the bridge.
“The most surprising thing for me has been learning how the bridge behaves on a day-to-day basis at the level of precision that we were never able to before,” says UW CEE professor Travis Thonstad.
Learn more:
Keeping watch on a one-of-a-kind bridge By: Julia Davis / Photos courtesy of Sound TransitMay 18, 2026Top image: A light rail vehicle crosses the I-90 floating bridge. CEE researchers build a digital twin of the I-90 Homer M. Hadley Memorial Bridge to monitor the world's first floating light rail cr...