Subway operator Tokyo Metro has said that maintenance subsidiary Metro Sharyo falsified measurements taken during an assembly process for wheelsets.
According to the announcement Wednesday, Metro Sharyo made the data appear to fall within standards. The company thought that such a change was acceptable if it was within certain limits.
Data was altered for 233 axles of 161 subway cars, out of a total of 11,000 axles of some 2,700 cars owned by Tokyo Metro.
The affected cars were used on eight Tokyo Metro lines such as the Ginza and Tozai lines. Also affected were some train cars of Toyo Rapid Railway in Chiba Prefecture and Saitama Railway in Saitama Prefecture, both of which commissioned Metro Sharyo for the work on their cars.
Tokyo Metro will continue using affected cars after confirming their safety through ultrasound inspections, except for two cars used on the Yurakucho and Fukutoshin lines with axles whose data far exceeded standard levels.
On Saturday, Tokyo Metro canceled one train on the Nanboku Line due to the data manipulation, but the train was shortly put back into service after its safety was confirmed.
Tokyo Metro said that the data manipulation will no longer affect its subway operations.
The problem came to light due to urgent inspections ordered by the transport ministry after the disclosure of data falsification by Japan Freight Railway.
Similar data falsification has also been found at the Toei subway service run by the Tokyo Metropolitan Government. A total of 467 axles of 156 cars were affected.
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