Rail safety issues and actions

Design of the automatic warning system (AWS)

Issue number: RO-2018-002-SI-03
Issue owner: Queensland Rail
Transport function: Rail: Passenger - metropolitan
Background: Investigation Report RO-2018-002
Issue release date: 15 April 2021
Current issue status: Closed – Partially addressed
Issue status justification:

The ATSB notes the safety action to change the auditory volume of the AWS for restricted signals verses green signals, but believes that this will not have a significant impact in reducing the risk of the safety issue as it does not help differentiate red signals from other restricted signals. The ATSB also appreciates that there would be substantial difficulty in redesigning the AWS to provide a clear distinction between the alerts that occur in response to signals with a red aspect compared to other restricted signals. However, the ATSB welcomes the safety action to introduce the European Train Control System (ETCS) and believes that this system will reduce the risk of SPADs where and when it is implemented.

Safety issue description

The automatic warning system (AWS) provided the same audible alarm and visual indication to a driver on the approach to all restricted signals (that is, double yellow, yellow, flashing yellow and red aspects). The potential for habituation, and the absence of a higher priority alert when approaching a signal displaying a red aspect, reduced the effectiveness of the AWS to prevent signals passed at danger (SPADs). This placed substantial reliance on procedural or administrative controls to prevent SPADs, which are fundamentally limited in their effectiveness.

Proactive action

Action number: RO-2019-002-NSA-050
Action organisation: Queensland Rail
Date: 15 April 2021
Action status: Closed

The Queensland Rail (QR) internal safety investigation into the 10 January 2018 SPAD occurrence at signal ME45 was completed in February 2018. The report included the following conclusions related to the automatic warning system (AWS):

  • It is likely the RTD [driver] unconsciously acknowledged the AWS restricted indication
  • If the AWS had prompted the Relief RTD to apply the train brake it is likely that the train would have stopped in advance or just past signal ME45.

The report also included the following safety actions that had already been initiated relating to AWS:[32]

Principal Human Factors Adviser to review available data to analyse RTD response to AWS audible indications and reaction times on both green and restricted signals.

Principal Electrical Engineer – Operating Assets to facilitate the decrease in volume of the AWS audible indication at a proceed signal aspect (green) and increase the volume of the AWS audible indication at a restricted signal aspect (double yellow, yellow, flashing yellow or red).

In addition, the report also included the projected introduction of the European Train Control System (ETCS) into the Citytrain network as a safety action to manage the risk of SPADs:

The [ECTS] project has reached the stage where expressions of interest from market leaders to partner with Queensland Rail to implement the new technology have been called.

The system encompasses automatic braking and enhanced control systems which will enable trains to safely travel closer together through the monitoring of the speed and position of trains and ensuring they stay within designated speed limits. This will positively impact on SPAD frequency.

In April 2019, the Queensland Government announced that the ETCS works package would be delivered by Hitachi Rail STS. As the future operator, Queensland Rail would be responsible for successfully integrating the cross-river rail project and ETCS Level 2 project into its rail network.

In March 2021, QR advised the ATSB of the following update regarding its the project to decrease in volume of the AWS audible indication at a proceed signal aspect (green) and increase the volume of the AWS audible indication at a restricted signal aspect:

[Following the initial internal recommendation] An action plan was drawn up for the whole fleet.

Responsibility for completion and progress of the project is being tracked utilising GRC action MA-3108 with an estimated completion date of 30/12/2023.

In relation to other action, QR advised:

In addition to improvements to the AWS system, Queensland Rail is currently working with project sponsor TMR, the Cross River Rail Delivery Authority and supplier Hitachi STS to determine an ETCS Level 2 implementation schedule for parts of the Queensland Rail network in South East Queensland. The design phase of the project has commenced.

ETCS Level 2 will provide an engineering level control for the mitigation of SPADs or exceedance of authority risk, where implemented. The system includes a Driver Machine Interface which displays maximum permitted speed and the distance to the applicable limit of authority (LOA) to the Rail Traffic Driver. Where the system detects that the rail traffic is exceeding the required braking curve to an LOA, warnings and if necessary, a brake intervention is automatically initiated. The braking curve and any required brake intervention are configured to prevent the rail traffic reaching a point of conflict where a collision with other rail traffic might otherwise occur.


  1. These actions were initiated following QR’s internal investigation into a SPAD that occurred at Roma Street in September 2017 (see also ATSB report RO-2017-012).
Last update 29 June 2021