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Crack in Shinkansen bullet train undercarriage could have led to derailment

A crack is seen on the side of an undercarriage frame of a Shinkansen bullet train. (Photo provided by JR West)

The crack found in an undercarriage of a Shinkansen bullet train was roughly 44 centimeters in total from one side of the undercarriage frame to the other, West Japan Railway Co. (JR West) announced on Dec. 19, almost breaking the frame, which could possibly have led to a derailment.

The crack was found in the steel frame of an undercarriage of the running Nozomi No. 34 bound for Tokyo from Hakata, Fukuoka Prefecture, on Dec. 11. The troubled Shinkansen train continued running for some three hours after abnormalities were first reported. JR West Vice President Norihiko Yoshie admitted to the operator's misjudgment when responding to the reports of an abnormality and apologized over the incident during a news conference on Dec. 19.

"We kept the train running even though irregularities were reported. We're taking this seriously," Yoshie said.

According to JR West, the undercarriage frame, manufactured by Kawasaki Heavy Industries Ltd., is made of two open-ended square steel parts welded together. The rim of each side is 8 millimeters thick, and together they make up the 17-centimeter by 16-centimeter frame. The bottom of the steel part was torn 1.3 centimeters in width and the crack on both sides measured roughly 14 centimeters from the bottom, leaving only 3 centimeters on the upper part of the frame intact. Since the frame was deformed due to the crack, the joint that transmits motor motions to the gears got displaced, leading to the color change and oil leak.

While it was the first case of this kind of abnormality involving a Shinkansen train undercarriage, many past incidents of cracks in undercarriages for regular passenger trains were found in welded parts. Similarly, there was a welded part on the bottom of the cracked Shinkansen undercarriage.

JR West has also revealed that a maintenance worker who boarded the Nozomi train at Okayama Station following the reports of irregularities on Dec. 11 suggested that the train should be stopped for an inspection. The company stopped short of revealing detailed exchanges between the worker and those at the Shinkansen general command center in Tokyo, however, saying that the company needs to investigate the maintenance crew's remarks and their intention as it could be an important point in the incident.

JR West Vice President Norihiko Yoshie gives a grim look during a news conference over the recent incident involving a Shinkansen train, on Dec. 19, 2017, in Osaka. (Mainichi)

Yoshie and other JR West executives made a deep bow at the outset of the press conference on Dec. 19, saying that the company was responsible for causing an extremely serious incident.

While they explained that such an incident was beyond their expectations, they admitted that allowing the train to travel to Nagoya Station from its initial departure point at Hakata Station without an inspection, although abnormalities were repeatedly reported, was seriously problematic.

When asked why the operator did not stop the train, the executives said the company did not recognize the situation as serious enough to affect the train operation and added that it is investigating the facts such as exchanges between the train conductor, maintenance workers and those at the command center, as well as a briefing between crew members of JR West and Central Japan Railway Co. when the former handed over the train to the latter at Shin-Osaka Station.

In response to a 2005 derailment on the JR Fukuchiyama Line, where 106 passengers were killed and 562 others were injured, JR West has worked on revising its safety management system. The Shinkansen operation also followed the in-house manual, but the undercarriage frame had cracked. JR West officials indicated during the news conference that the company would be reviewing the manual as well as inspection measures, and conduct employee training to make sure that train operations are suspended when several reports of irregularities including abnormal smells or noises are made.

Kazuhiko Nagase, visiting professor at Kanazawa Institute of Technology specializing in railway system engineering, pointed out that the crack was the result of typical metallic fatigue and was not something that happened due to the Dec. 11 run. "It (the frame) was barely intact in the end," he said.

Japan Transport Safety Board Chairman Kazuhiro Nakahashi raised questions over JR West's response to the latest incident during a regular news conference on Dec. 19, saying that the operator should have stopped the train when the crew detected abnormal noises and smells.

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