The South Improvement Alliance engineers did not effectively identify and record that the interface between CA74C and CA74D was the fouling point between the Up Main line and No.1 Platform Road and thus did not recognise that the rear of a train sitting on the Up Main line at this location would foul No.1 Platform Road. The design deficiency was caused by a long standing practice of not explicitly recording the clearance point on the Signal Arrangement Plan, Track Insulation Plan or in the Control Tables.
ARTC signalling system has been in place for the last 3 years and this was first recorded event of this type. Signal design errors are rare occurrences due to extent of validation and quality control processes. Following this investigation all relevant design issues have been identified and deficiencies have been corrected. The ATSB has reassessed the risks associated with this safety issue and while there is still a minor risk of serious injury or fatality, the ATSB believes the responses provided by the ARTC and RailCorp are adequate to address this safety issue.
The Australian Rail Track Corporation has advised that the following actions were taken with respect to future signal design work.
Update the Track Standards to adequately identify the process for determining the fouling point. Provide consistent references in the Signals Standards to the Track Standard for the fouling point. Rollingstock Standards and approvals to include control measures for cases were the overhang exceeds 3.0 metres. The Track Design Engineer is nominated as the responsible authority for the design, calculation and identification of the location of the fouling point. Where the track design is not changed, then an appropriately competent track design engineer shall perform the task based on the as-installed infrastructure. This information to be recorded and configuration managed.
The use of a plate to permanently identify the location of the fouling point be considered. The Track Maintenance Standards, Examination Standards and Work Schedules be amended to include verification of the clearance after specific maintenance activities or events. Clearance Points to be explicitly identified on the Signal Arrangement Plan, Track Insulation Plan. A table be included in the Control Tables to identify Clearance Points and their associated requirements. Signal Design Standards to be updated for the above. Ensure Compliance with the Signals Standard for Track Insulation Plans to be scale drawings in the longitudinal and lateral axes.
The Australian Transport Safety Bureau is satisfied that the action taken by the Australian Rail Track Corporation adequately addresses the safety issue.
