TOKYO -- One of Japan's celebrated shinkansen bullet trains was only 3cm away from a possible disaster, including derailment, its operator West Japan Railway (JR West) has revealed.
A 14cm crack was found on Dec. 11 in the undercarriage of one of the trains. Had it severed the whole 17cm steel frame, the train's wheels could have left the tracks, experts said.
On Wednesday, Tatsuo Kijima, president of JR West, apologized for the incident, saying, "We acknowledge that this betrays the trust in the shinkansen's safety and I deeply apologize."
The trouble occurred on Dec. 11 on the Tokyo-bound Nozomi No. 34 from Hakata in the southern prefecture of Fukuoka. At around 1:50 p.m., when the train was at Kokura Station, the first stop on the five-hour journey, a cabin crew selling beverages noticed unusual smells in the carriage and reported the matter to the conductor.
As a precaution, a maintenance employee boarded the train at Okayama Station, the fourth stop. He noticed abnormal sounds and recommended an inspection at the next stop.
However, when the engineer discussed the matter with the Shinkansen General Control Center in Tokyo -- the nerve center that oversees all shinkansen traffic throughout the country, similar to an air traffic control center -- they concluded that since no immediate threat to the operation of the train could be detected, the journey should continue.
The bullet train continued to operate at high speeds until it was halted at Nagoya Station.
Following the incident, the Japan Transport Safety Board -- a committee under the Ministry of Land, Infrastructure, Transport and Tourism that investigates train, airplane and ship accidents -- was convened. The committee designated the incident as "serious" -- the first such designation since the shinkansen was introduced in 1964.
The board's Chairman Kazuhiro Nakahashi on Tuesday said that it is "highly unlikely that the crack formed suddenly."
"As there are small areas of damage in the undercarriage, I assume that [the crack] had expanded over the course of multiple runs," he added.
To prevent a recurrence, JR West will inspect all undercarriages, mainly the area where the crack was found in the latest incident.
It is also considering installing sensors on a portion of the undercarriages, which could detect abnormalities automatically.
An internal investigation has begun, including going back to the companies that supplied the chassis, gearbox and various parts.
Manufactured in 2007 by Kawasaki Heavy Industries, the undercarriage's chassis holds the axles; two axles support the carriage's body.
The steel for the chassis was supplied by JFE Steel. Other suppliers include Nippon Steel & Sumitomo Metal, which made the gearbox and Mitsubishi Electric, which provided the parts that connect the motor to the tires.
Railway experts expressed concern about the crack possibly causing a derailment.
Kazuhiko Nagase, a visiting professor of railway system engineering at the Kanazawa Institute of Technology, described undercarriages as "extremely important parts for the running of a shinkansen."
"The crack was bigger than we can possibly imagine," he said. In the worst case scenario, there was a possibility that the crack could have jolted the axles out of alignment, which could have led the "wheels to leave the tracks."
Because shinkansen trains travel at high speeds, he added, "damage from a derailment would be immeasurable."
Another expert, Sumiaki Otsuyama, a professor of railway engineering at Osaka Sangyo University, pointed to the need for an early detection system.
Otsuyama noted that it is difficult to discover every small bit of damage through visual inspections conducted before the service starts.
He urged railway companies to "also consider an early anomaly detection system by installing sensors capable of detecting subtle abnormalities in oscillation and temperature on undercarriages and tracks."
The shinkansen system has been the symbol of Japan's engineering prowess since it started operations in the 1960s. The bullet train's operators take great pride in the fact that it has had zero fatal accidents since the system's inception.
Regarding the fact that it took three hours from the time the conductor and engineer identified the abnormalities until the train was stopped, President Kijima said, "This is a major issue. We will determine the reason we could not stop the train."