Photo/Illutration Crowds wait at 10:32 a.m. by the entrance gate in JR Sendai Station in Sendai, Miyagi Prefecture, for the operation of the Shinkansen to resume on Sept. 19. (Miya Yoshimura)

While traveling at approximately 315 kph, two carriages of a Shinkansen running between Furukawa and Sendai stations in Miyagi Prefecture suddenly decoupled, bringing the train to an emergency stop.

Now experts are trying to figure out what went wrong with the Tohoku Shinkansen Hayabusa-Komachi No. 6. The mishap occurred shortly after 8 a.m. on Sept. 19.

“I felt it stopping silently. I wondered why,” said Hideo Matsumura, a 56-year-old national public officer who lives in Morioka city.

Matsumura was on the Hayabusa Shinkansen, which had linked up with and was pulling the Komachi Shinkansen. 

“We learned about the situation through an announcement, and the atmosphere inside the train became a bit chaotic,” he added.

A man in his 20s who was in the same train car said, “I thought we had just stopped at a station.”

The two separated trains, which had come to a stop approximately 300 meters apart, were able to move again, separately, toward Sendai Station after 11:40 a.m.

East Japan Railway Co. (JR East) explained the situation at a news conference that evening.

The train’s couplers are designed to automatically lock and connect electrically, allowing the connected train segments to operate as a single unit.

There were no abnormalities found when the Hayabusa-Komachi No. 6 departed from Morioka Station, where the Hayabusa and Komachi trains had connected. There seemed to be no issue with the coupling.

The couplers are designed to withstand a pulling force of about 50 tons.

Neither of the disconnected couplers showed any visible abnormalities. Additionally, the separation system is designed to activate only at speeds below 5 kph, so it is unclear why the trains disconnected while traveling at more than 300 kph.

At the time, there was no driver on the Komachi train and only one conductor aboard.

When a separation occurs, the automatic brakes are applied.

The system is designed to apply stronger brakes on the rear train cars, so there was no risk of a collision between the two separated segments.

JR East plans to conduct inspections on all 96 coupled train units and will investigate the data of the separated trains to identify the cause.

This year, there have been a series of troubles on Shinkansen, including overrunning stations, broken overhead wire equipment and derailments of maintenance vehicles.

ELECTRICAL SYSTEM TROUBLES?

“It doesn’t look like a large external force damaged the coupler itself,” said Hitoshi Tsunashima, a specially appointed professor of control engineering at Nihon University.

Instead, he believes, “It’s more likely that a malfunction in the electrical system triggered a separation signal that shouldn’t have occurred.”

The train cars decoupled after traveling about 140 kilometers from Morioka Station, where the Hayabusa and Komachi trains were connected.

At the time of the separation, the trains were traveling at 315 kph.

Ryo Takagi, a professor at Kogakuin University, said, “In a worst-case scenario, the two decoupled Shinkansen trains could have collided. It was good that no one was injured.”

Shinkansen mishaps have been occurring in succession due to errors in the scope and methods of inspections.

“Due to decreased demand for rail services during the COVID-19 pandemic, the workforce was reduced, primarily among veteran staff," Takagi said. "After a rapid recovery of demand in the post-pandemic period, it is possible that transferring skills didn’t go well. I’d like to focus on whether human factors are related to these accidents.” 

(This article was written by Ikuko Abe, Ayateru Hosozawa and Kazuki Uechi.)

Related News