CASE C21 · JP · 2025
MLIT Kinki Regional Bureau: cost and schedule comparison for bridge inspection with a 360° obstacle-sensing drone
MLIT's Kinki bureau compared cost and schedule for bridge inspection with a 360° obstacle-sensing drone against inspection vehicles on three bridges. Estimated schedules shrank by roughly 40–70%, but cost savings were only about 10–20%. Flights stop in wind or rain, and hammer-sounding is still needed where falling debris could harm the public.
| Owner | MLIT Kinki Regional Development Bureau |
| Provider | — |
| Location | Kinki region, Japan (Aji Viaduct 750 m, Yamatogawa Bridge 250.5 m, Yamatogawa-kita Viaduct 510.5 m) |
| Aircraft | Skydio drone with 360° obstacle sensing (model not stated) |
| Sensors | RGB camera (cracks down to 0.1 mm) |
Before
Close visual inspection from an under-bridge inspection vehicle.
With drones
A drone able to fly without GNSS under the deck photographs girders, piers, slabs and bearings; contractor quotes were compared with the conventional method.
Outcomes
| Metric | Value | Basis |
|---|---|---|
| cost (Aji Viaduct) | ¥4.53M → ¥4.115M (about 10% lower); 13 → 8 days | Estimate |
| cost (Yamatogawa Bridge) | ¥3.72M → ¥3.101M (about 20% lower); 10 → 4 days | Estimate |
| cost (Yamatogawa-kita Viaduct) | ¥8.55M → ¥6.932M (about 20% lower); 25 → 8 days | Estimate |
Caveats & limits
- Figures are contractor estimates (July 2025 quotes), not measured results.
- Cost savings are modest (about 10–20%) even though days fall sharply.
- Flights are impossible in strong wind or rain, so schedules need slack; hammer-sounding is still required where defects could affect third parties.
Sources
- 360度周囲を認識するドローンを用いた橋梁点検支援技術MLIT Kinki Regional Development Bureau Full text read
Sources checked: 2026-10-22