The Shinkansen Nozomi No. 34, originating in Hakata and bound for Tokyo, suspended its journey at Nagoya on Dec. 11 after a crack was found in the undercarriage.

Given the gravity of this mishap, which could have resulted in a serious accident, we must question the operator's commitment to safety.

West Japan Railway Co. (JR West), the operator, revealed at a news conference on Dec. 19 that the crack measured 16 centimeters at its longest, which could have ruptured and caused a derailment, had the bullet train kept running.

About 1,000 passengers were on board.

This was an unprecedented situation in the Shinkansen's half-century of service. The Transport Safety Board has designated it as the first "serious incident" involving a bullet train and launched an investigation.

Aside from the obvious need to determine the cause of the crack, JR West must also thoroughly examine its daily checking procedures and emergency response system.

The main issue in this case was that it took more than three hours to suspend the journey after an abnormality was first detected.

The train was departing from Kokura Station (next to Hakata) when a staff member smelled "something burning" and reported it to a conductor, who passed it on to the General Control Center in Tokyo.

But the train kept running, until a passenger complained of a "haze" in the car between Fukuyama and Okayama.

Three maintenance staffers boarded the train at Okayama and confirmed abnormal noises in some cars.

And yet, the train continued on its journey. When the jurisdiction changed from JR West to Central Japan Railway Co. (JR Tokai) at Shin-Osaka Station, the staff in charge reported "no abnormalities."

After the train left Kyoto Station, the unpleasant odor came back. A subfloor examination at Nagoya Station revealed an oil leak, and the operation was finally suspended.

According to JR West, any abnormality during a journey is reported to the General Control Center in Tokyo, which issues operational instructions.

But should anything go amiss, staff members should try to determine the source of the trouble as soon as the train pulls into the next station.

A JR West representative told the news conference, "From now on, we will never hesitate to stop a train if we cannot confirm the absence of abnormalities."

But we do not understand why the service was not suspended immediately in this case, and wonder what sort of communications were exchanged between the train staff and the Tokyo control center. These matters need to be examined in detail.

There are more than 350 Shinkansen runs per day between Tokyo and Shin-Osaka. At certain times of the day, the trains depart or arrive at intervals of a mere few minutes.

Could the operator have prioritized maintaining this tight operating schedule over safety? Another concern is whether sufficient time is always allotted to safety-related communications between the jurisdictions.

We ask JR to go through every questionable step that was taken in this case.

And we suggest that independent, third-party experts be included in the investigation.

After the major Takarazuka Line derailment fiasco of 12 years ago, JR West drew up a safety improvement plan and vowed to put safety above all. We hope this spirit has not been forgotten.

--The Asahi Shimbun, Dec. 20