East Japan Railway Company plans to carry out reinforcement work on Shinkansen lines following an extensive suspension of bullet train services last week.
The company said the suspension last Tuesday was caused by damage to a part that holds the overhead power cable in place. A resulting power outage led to the cancelation for extended hours of more than 280 trains on parts of the Tohoku, Hokuriku and Joetsu Shinkansen lines.
At a news conference on Tuesday, senior officials of JR East apologized for causing trouble to passengers.
They said the repair work will be carried out by the end of July on all Shinkansen lines under its jurisdiction.
As a tentative measure, the company will replace the type of part in question in the section between Tokyo and Omiya in neighboring Saitama Prefecture.
In other sections, it plans to put a new metal fitting near the part in order to prevent the overhead power cable from dangling even if a similar problem occurs again.
Under the company's standard maintenance policy, the replacement cycle for this type of part is every 30 years. But the part that broke had been used for 38 years.
The officials also said the subsequent inspections of the same kind of part at 490 locations revealed that more than half had been used for more than 30 years.
One of the officials said the company has had replacement plans depending on the condition of individual parts and the environment in which they have been used.
He added that the company will review the plans following the latest trouble, and suggested that the part will be replaced with a spring type device, which would have a simpler structure and have a lower risk of breaking.