The Electrical & Mechanical Services Department has completed an investigation into the incident involving the new signalling system testing on the Mass Transit Railway (MTR) Tsuen Wan Line on March 18.

The investigation identified a programming error during software rectification of the new signalling system by the system contractor at the design and development stage as the cause of the incident.

This error caused a failure to establish the data of the crossover track at Central Station after the switchover from the primary zone controller to the warm-standby tertiary zone controller.

The Automatic Train Protection system therefore could not prevent two trains from entering a crossover track at Central Station at the same time, leading to a train collision.

After a thorough review of the report submitted by the MTR Corporation's Investigation Panel in June, the department accepted the investigation outcome on the cause of the incident, which was the programming error in the software of the new signalling system as a result of multiple implementation errors by the system contractor.

The department will closely monitor the full implementation of improvement measures proposed by the panel.

Dynamic train testing of the new signalling system on the MTR Tsuen Wan Line can resume after the MTR has fully completed the remedial work and the department has confirmed the safety of the system.

Click here for the department’s report.