02-06-2025
Same circuit board used in two bullet train decouplings
The decoupled Hayabusa and Komachi bullet trains in Tokyo's Arakawa Ward on March 6 (Yasumasa Kikuchi)
East Japan Railway Co. (JR East) has revealed that two recent decouplings of Tohoku Shinkansen mid-journey involved different Komachi trains that used the same electrical circuit board, which may have triggered the malfunctions.
Following the first decoupling in September, JR East determined that a small metal fragment left over from the manufacturing process may have caused a false unlocking signal by entering the coupler's control switch.
In response, company engineers inspected all 96 train units capable of coupled operations and cleared any metal fragments. They also removed parts behind the control switch for modifications to prevent a recurrence.
One of these modified parts--a circuit board from the first train malfunction--was later installed in the train that experienced the second decoupling in March.
The circuit board in question has been removed and is now undergoing a thorough investigation to determine whether it was responsible for both decoupling mishaps.
In the second incident, officials confirmed that the lever designed to unlock the coupler repeatedly failed. However, the exact cause for the malfunction remains unknown.
The recent discovery involving the circuit board has prompted JR East to re-examine whether the first incident was actually triggered by a loose metal fragment.
In addition to its own investigation, the company is cooperating with a probe by the Japan Transport Safety Board, which has classified the incidents as serious. Along with safety concerns, the malfunctions inconvenienced hundreds of thousands of passengers as hundreds of trains were canceled.
Shortly after the suspension of operations that followed the second incident, JR East resumed coupled train operations using temporary preventive measures.
It installed additional metal components designed to physically prevent the coupler from disengaging trains, even in the event of an electrical signal malfunction.
JR East President Yoichi Kise has announced plans to introduce a permanent double-locking mechanism in the safety system to prevent mid-operation decoupling.
