Tuesday, September 23, 2025

Safety Message – Managing Track Stability

If track stability is not effectively managed, it can lead to sudden infrastructure failure, often without clear visual warning signs. These failures can potentially cause derailments or collisions, leading to injury, fatalities, and/or major disruption to operations.

Managing the risk of track misalignment requires a combination of good design, operational controls and most critically, proactive maintenance and monitoring.

ONRSR expects Rail Infrastructure Managers (RIMs) to have clearly defined strategies for monitoring and controlling track stability. This includes identifying high-risk locations, applying targeted inspections and setting operational triggers.

While AS7643 Track Stability provides guidance on requirements for track stability management, recent incidents and ONRSR’s regulatory activities have shown that these practices are not always effectively implemented. This Safety Message highlights some key aspects to managing track stability.

Identification of High-Risk Locations and Hot Weather Seasonal Preparation

Identification of high-risk locations is fundamental in preventing misalignments. It enables early rectification of defects, or application of operational restrictions. In some recent cases, derailments caused by track lateral stability issues occurred where high-risk locations were not identified.

In preparation for the approaching high-risk hot weather period, ONRSR expects that each RIM should be able to demonstrate, with a reasonable degree of certainty, the following:

• For CWR and LWR track assessments of the stress-free temperature (SFT) by either:
  - Direct SFT management (i.e. verse testing)
  - Indirect SFT analysis (i.e. alignment monitoring and rail creep measurement, and/or joint gap measurement)
• For jointed tracks, assessment of the track rail creep and joint gaps
• Identification of potential initiators such as:
  - Recent disturbances of ballasted track (i.e. tamping, reconditioning, ballast cleaning)
  - Rail fixed points and potential rail longitudinal bunching points (i.e. level crossings, turnouts, bridge ends)
  - Locations of poor track lateral strength (i.e. poor ballast confinement, poor ballast profile, poor sleeper/fastener condition)
  - Bog/mud holes
  - Poor rail condition (i.e. corrugations, poor rail/joint alignment)
  - Insufficient fastening resilience
  - Uneven rail creep (although rail creep can occur anywhere, it is most prevalent on track grades)
  - Poor rail joint gap management
  - Locations of poor track geometry and small radius track curvature.

Note: Although poor management of stress-free temperature (and joint gaps/rail creep in jointed track) is a major factor in misalignments, the risk assessment for any section of track must consider all contributing factors which influence track stability, not stress-free temperature alone.

RIMs should undertake an assessment to manage the risk of track instability and determine the track lateral strength is above acceptable thresholds. Additionally, the SFT (or rail joint gaps, as appropriate) are managed within an acceptable tolerance range both above and below the target SFT (or rail joint gaps, as appropriate).

Controls and Response Measures

Once high-risk locations have been identified, RIMs should implement measures to:

• Manage the risk of track instability at high-risk locations through appropriate physical work (i.e. re-adjusting the thermal stress in the rails, resurfacing to place the track on the correct alignment, rail grinding, and correction of bog hole).
• Plan for operational controls (e.g. speed restrictions, additional monitoring/inspections) which are to be implemented in the case of hot weather.

Post-Incident Response

If a track misalignment occurs, RIMs are expected to investigate to determine the cause and identify any necessary corrective actions. These actions include, but are not limited to:

• Undertaking any repairs to prevent a recurrence at that location (and similar locations where this risk has also been identified).
• Implementing changes to the safety management system, where appropriate.

Action

RIMs are encouraged to review their existing track stability management practices, ahead of the high-risk hot weather period, and ensure they understand the risk across their entire network.

Key documents

RIMs are encouraged to review additional guidance material below:

• AS 7643 - Track Stability
• Safety Message - Managing your track infrastructure assets
• Safety Message - Management of change