[Press Release] About municipal Subway Blue Line Derailment Accident Investigation Report

　Regarding the derailment of the municipal Subway Blue Line that occurred on June 6, 2019, an accident investigation committee was established within the Transportation Bureau to conduct detailed analysis of the cause of the accident and to examine measures to prevent recurrence.
　We are pleased to announce that we have compiled a survey report.
　On this occasion, we apologize again for any inconvenience and inconvenience to the citizens and users, and based on the discussions at the Accident Investigation Committee, we are truly effective based on this report. We will work on effective recurrence prevention measures and strive to regain the lost trust.

[Points of the Accident Investigation Report (Summary)]

Cause of the accident (P.15)
1 Direct Cause of derailment
　After inspection of the transit device by the authorities and maintenance staff after the commercial operation the day before the accident, one of the three crossover materials, which were part of the equipment, was still fixed on the main line rail. The train wheel got on the material.
2 How the crossover material was fixed on the main line rail
　Of the three working teams, the staff who inspected the relevant crossover material completed the inspection while fixed on the main line rail, and inserted the chain locking device pin (the alarm, buzzer, etc. stopped).
　After that, it was judged that the work was completed by turning off the alarm and the like was turned off and the buzzer was stopped, and it was not confirmed that the transceiver body was in its original storage position.

Analysis of the cause of the accident (P.16)
1 Insufficient understanding and awareness of the work content and regulations of the work implementer.
2 The work procedure and final confirmation method were not clear.
3 The division of roles in the work was not functioning.
4. The organization was not able to grasp the actual situation.

Measures to Prevent Recurrence (P.20 Report)
1 Emergency action
　Implemented emergency measures to prevent recurrence to solve problems with transit equipment and urgent measures to ensure safe operation
(1)　Preparation of procedures for transit equipment inspection, clarification of work procedures, and clarification of the role of the person in charge of work
(2)　Clarification of final confirmation method, such as creating a check sheet for handling cross-transfer equipment
(3)　Reinforce compliance with rules, such as notification to all employees
2 Measures to be implemented in the future
(1)　Establishing regulations and strengthening management
(2)　Fundamental Review of Staff Education
(3)　Creation of a system for promptly collecting and sharing information on safety
(4)　Efforts to further improve the safety of transiting equipment
3 Reform of the organizational culture toward “safety that is not loose”

The full text of the investigation report is posted on the Transportation Bureau website.
https://translate-en.city.yokohama.lg.jp/kotsu/kigyo/anzen/blueaccident.html