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The train could be moved with the carriage doors open

Issue number: RO-2014-005-SI-01
Who it affects: Train passengers
Issue owner: Metro Trains Melbourne
Operation affected: Rail: Passenger - metropolitan
Background: Investigation Report RO-2014-005
Date: 27 April 2016

Safety issue description

As designed, the traction interlock automatically deactivated after a period of time. This allowed traction to be applied and the train to depart with the carriage doors open.

Response to safety issue
MTM advised the ATSB that subsequent to the incident MTM has made no changes to the traction interlock system on the rolling stock, but has commenced a risk review of the traction interlock timing.

ATSB comment/action in response
The ATSB believes that the traction interlock system in its present configuration presents a risk to passengers and suggests that MTM institute additional risk mitigation measures until the risk review is completed. Accordingly, the ATSB issues the following Safety Recommendation.

Recommendation

Action organisation: Metro Trains Melbourne
Action number: RO-2014-005-SR-030
Date: 13 July 2016
Action status: Released

The ATSB recommends that MTM considers a modification of the traction interlock override system to incorporate additional risk mitigations.

Correspondence

Date received: 26 July 2016
Response from: Metro Trains Melbourne
Action status: Released
Response text:

MTM agrees with the recommendation that it consider a modification of the traction interlock override system, in the terms suggested. It has done so.

MTM has now completed a risk review of the traction interlock timing. It is considering proposals to modify the interlock override system on both X’Trapolis and Comeng Fleets which have the same functional design.

Proposed changes following this risk review

The proposed steps are to undertake circuit modifications and install a key operated override switch. When implemented, these measures will allow a train to gain traction control in circumstances where a door appears to be open, but will differ from the arrangement at the time of the incident in that they require an additional manual intervention from the driver.

Circuit modification

Circuit modifications will necessitate the removal of the existing timer relay circuit that provides for the functionality to be restored after a 60 second delay. Therefore if a ‘door open’ condition is detected following the initiation of the ‘door close’ command, the circuit will inhibit traction without time limitation, until the key switch is operated to reinstate traction.

Key switch

The key switch will allow a train to obtain traction (whether in the usual running of passenger services, or otherwise by the manual intervention of a person authorised to have a copy of the key. The functionality will be such that once operated to regain traction control, it will be mechanically locked in that position and remain so until reversed to the normal train operating status.

During the running of a train, MTM’s systems will be such that the key can only be operated by a driver properly authorised and having the appropriate operating key. It should be noted that this is a similar configuration currently on the Siemens fleet.

Proposed implementation period

For Comeng trains within the MTM fleet, the installation of the proposed solution is being undertaken as part of the Comeng Life Extension program and is planned to commence by December 2016.

For X’Trapolis trains, the implementation works are scheduled to commence after circuit validation by the train designer ALSTOM. For a number of reasons, MTM cannot proceed to make these alterations without ALSTOM approval.

In discussion with DEDJTR (Department of Economic Development, Jobs, Transport and Resources), the body with overall funding responsibility for the Melbourne metropolitan train network, it is proposed that new X’Trapolis trains being ordered would be the first fitted, with changes to other X’Trapolis trains being the subject of further review of funding options and

   
Current issue status: Safety action pending
Status justification:

ATSB accepts MTM’s proposed actions on this safety recommendation. However, until the proposed circuit modifications are completed, the ATSB will retain the status of this safety issue as ‘pending’.

 
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Last update 22 August 2016