Tokyo Metro Co. demonstrated a drone inspection of subway tunnels to reporters Tuesday at its training facility in Koto Ward, Tokyo. The subway company started using drones to inspect tunnels on the Hanzomon Line on Feb. 6. The aim is to improve the safety of tunnels by using drones to inspect in detail the upper parts of tunnels and vents, which are difficult for people to see.
The drone, 22 centimeters in diameter and weighing 1.15 kilograms, is enclosed in a plastic lattice sphere that protects it against crashing into walls. The drone can fly for up to five minutes continuously at an altitude of 50 meters.
A Tokyo Metro employee flew a drone through a 5.5-meter-high training tunnel and used onboard cameras to capture images of areas near the ceiling and vents. The video was displayed on a monitor placed on the track, and other employees checked to see if there were any problems, such as wall deterioration.
The total length of Tokyo Metro's nine subway lines is 195.1 kilometers, with tunnels accounting for 85% of the total. Currently, workers inspect high places in tunnels by looking up from the tracks or by using scaffolds or vehicles equipped with elevating platforms, making repairs as needed.
The drones can get closer to the tunnel walls, making inspection work more efficient and reducing costs. The videos can be stored for further analysis. The company plans to introduce drone inspections on all of its routes in the future, including on the Marunouchi Line within fiscal 2020. "We want to use drones to do more for safety," a company official said.
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