Keywords: safety, accident investigation, automated guideway transit, automatic train operation.

The Japan Transport Safety Board (JTSB) is a multi-modal investigation organization responsible for carrying out investigations into aircraft, railway and marine accidents. We contribute to preventing the occurrence of accidents and mitigating the damage caused by them, thus improving transport safety. As the recent representative example of our activities, we pick up the case of a collision accident of an automated guideway transit (AGT), in which the automatically operated train ran in reverse at a terminal station and collided with the buffer stop.

The purpose of this abstract is to set out the contents of the investigation reports on that accident made publicly available by the JTSB in 2020 and 2021. We show how the accident investigation was performed with the cooperation of the experts and the results of the investigation, such as the underlying cause of the accident and the measures to prevent the similar accidents.

It has been found that a wire which transmitted the command signal of the running direction was cut off with a ground fault to a stainless steel member of the carbody. The reason why the unmanned train ran in reverse against the right direction was the breaking of a wire which transmitted the command to the on-board motor controllers. It is very simple, but it is thought that there is the fundamental cause of this accident with the motor control system, that was designed following the former manned operation vehicles. Furthermore, we investigated the underlying causes of the accident, and pointed out that they were in the designing process of the vehicle made by the railway company, a vehicle maker and device manufacturers, which induced insufficiency of careful safety analysis.

The driverless automatic train operation system without a human error is believed to be more reliable than the conventional manned operation, but this accident reminds us of the importance of the hazard analysis in order to realize a fail-safe transport system. This accident should be a warning for the design and the safety evaluation of AGT systems used widely in the world today.

The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) started the Council on Accident Prevention of Automated Guideway Transit with seven AGT companies with reference made to the JTSB’s report of safety information. The safety of the driverless automatic train operation system including the line where the reverse running accident happened has already been confirmed in the MLIT’s Council.

download the full-text of this paper (PDF, 6 pages, 327 Kb)

go to the previous paper
go to the next paper
return to the table of contents
return to the volume description