A conductor, who was not qualified to drive the train, sat in the driver’s seat during his three-minute absence, in breach of the rules

A driver on one of Japan’s shinkansen bullet trains is facing disciplinary measures after he abandoned his cab to go to the toilet while the train was carrying passengers and travelling at 150km/h.

The 36-year-old driver, who has not been named, reportedly had a stomachache and asked a conductor to take his place while he went to the toilet.

Related: Game of thrones: commuter sells seat on crowded Tokyo train