A safe, airborne railroad tunnel inspection technology called SATES [Safe Automated Tunnel Evaluation System] was developed, deployed, and evaluated to address key railroad tunnel inspection needs in the field.  SATES technology demonstrated capabilities to provide comprehensive, 3D, colorized tunnel liner measurements at high resolution to evaluate surface deterioration and subsurface moisture, including difficult access tunnel ceiling evaluation.  Novel SATES UAV deployment and innovative sensors produced the world’s first surface + subsurface UAV measurements in a tunnel.  Among other features evaluated, SATES detected and located subsurface water behind concrete tunnel liners, surface concrete tunnel deterioration features (spalls, cracks, etc.), and virtualized 3D tunnel geometry as a dense, colorized point cloud.  The custom SATES UAV airframe and purpose-built sensor deployments were integrated specifically for railroad tunnel inspection applications.  The SATES UAV performed tunnel safety measurements untethered, contact-free, and reference-free, showcasing convenient scan capabilities at two field test sites.  SATES sensing technologies accurately measured tunnel geometry within inspection tolerances, including difficult access features in tunnel ceilings (which are often dangerous and inconvenient to inspect via conventional means).  SATES comprehensively documented tunnel deterioration features and provided information about excess water in concrete tunnel liners (linked to tunnel deterioration phenomena).  In future research, Artificial Intelligence [AI] technology can be added to streamline the inspection process.

The final report is available.