Greater Tokyo, with a population of more than 30 million people about a quarter of Japan's total -- is notorious for its packed trains and subways during peak morning rush hours
Local media reported that some injuries — the first resulting from an accident involving an automated train in 30 years — appeared to be serious but non-life-threatening.
The train hit the buffer stop at Shin-Sugita station after travelling the wrong way for about 20 metres (65 feet), Akihiko Mikami, president of the train operator, said in a midnight press conference.
The station is a terminal of the self-driving Kanazawa Seaside Line in the port city of Yokohama.
Mikami added that the operator has shut down the line and it was uncertain when services would be resumed.
Compared to self-driving cars that have recently taken the road in several countries on a test basis, automated trains have a relatively long history in Japan.
Among accidents that have made headlines are a collision involving an autonomous Uber vehicle that killed a pedestrian and a fatal crash that involved electric car maker Tesla’s “Autopilot” feature, both of which occurred last year in the United States.
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