Queensland Rail's process for the installation of signal aspect indicators (SAIs) did not provide sufficient detail to ensure consistent and conspicuous placement of SAIs at station platforms. This problem, combined with an SAI’s non-salient indication when the platform departure signal displayed a stop indication, increased the risk that an SAI would not be correctly perceived by a train guard.
The ATSB notes that, although limited additional procedures or guidance has been developed to assist with the placement of SAIs, the risk of this safety issue has been reduced to some extent.
In January 2022, Queensland Rail (QR) advised:
Queensland Rail (QR) has an established signal sighting committee that reviews the placement of signal (and signal aspect indictors) across the network. The placement of an SAI is a signal and is treated the same for signal positioning. In the context of built urban environment with pre-existing station design and location challenges, then a consistent prescribed placement location may pose the reverse problem of the location not meeting the signal sighting principles…
During 2020 and early 2021, QR updated the three safety management system documents that are used by the committee as listed below...
- Signalling Positioning Principles Standard MD-10-95 (Version 4 implemented from 24/05/2021)- Signal Sighting Committee Procedure MD-12-252 (Version 4 implemented from 16/04/2020)- Signal Sighting Form MD-14-499 (Version 3 implemented from 18/03/2020)
The committee comprises of a Senior Rail Safety Advisor (Representing Rail Safety Aspects), Signalling Test and Commissioning Coordinator (Representing Signal Engineering) and an improvement to include two Senior Guards with at least one Representing the AFULE for the sighting of SAI’s for optimum placement.
The committee’s role is to consider operational issues relating to the optimal locations and visibility of signals and to assess the sighting and visibility risks associated with the placement of the signal. The committee’s recommendation may require the placement of SAI’s where the signal cannot be clearly sighted by the Guard from the rear end of a six car NGR Train, or the middle of a six car QR Train. Consideration is given by the committee for unobstructed sighting of the SAI’s by platform or station infrastructure, personnel standing on the platforms or platform / station lighting interference.
QR highlights that the historical nature of the infrastructure may not always allow for a consistent place of SAI’s across the network and utilises the mixed expertise of the signal sighting committee to best determine the appropriate location of any SAI.
The updated Signal Sighting Form (MD-14-499) demonstrates the required assessment items to be conducted and the characteristics of the SAI to be installed to ensure visibility.
These updates and activities by the signal sighting committee during 2020 and 2021 demonstrate the process to which the signal sighting risk is managed and how the business utilises a range of stakeholders including end users to best place SAI’s across the network when required to minimisze the chances of incorrect identification.
The ATSB recognises that, due to the existing building environment, there can be challenges with the installation of new SAIs. The ATSB also notes that, since the installation of the SAIs at Park Road, the signal sighting form has been updated to include reference to ensuring that SAIs are at a minimum height of 2,400 mm (associated with the requirements of MD-12-330 (Standard – SEQ High level station platforms).
The ATSB welcomes the projected introduction of the European Train Control System (ETCS) and believes that this system will in the long-term eliminate the need for SAIs in the Brisbane suburban network. The ATSB also notes that, following the introduction of NGR trains in 2017–2019, there is likely to be limited requirement for the introduction of new or modified SAIs in the short to medium term, and there would be some difficulties associated with moving the placement of existing SAIs. In addition, since the introduction of NGR trains, guards are now more familiar with the locations of SAIs and the limitations associated with relying on the allright signal provided by station staff at suburban station platforms. This is consistent with the decrease in the rate of start against signal SPADs.
Nevertheless, the ATSB still considers there is some risk associated with inconsistent (and in some cases less than conspicuous) placement of SAIs at station platforms, which could be exacerbated if any further SAIs are required to be installed or relocated. This is in contrast to the level of guidance provided for the placement of signals. Although QR have advised that signal sighting committees consider sighting issues when agreeing on the placement for an SAI, there is still no detailed guidance available in the relevant procedures and checklist to provide more assurance of suitable placements in the future. This would be a relatively simple problem to address.