Rail safety issues and actions
Safety Advisory Notice
|Date issued:||29 January 2008|
|Safety action status:|
|Background:||Why this Safety Advisory Notice was developed|
The track had been maintained based on the assumption that rail creep is sufficiently homogenous in open track to be manageable if monitored at 500 m intervals. It is likely that the rail creep in the area of the derailment was not homogenous as a result of long term and recent track work. Ballasted track structure based on continuous welded rails is sufficiently non-homogenous to enable bunching points to develop over time in open track. If localised rail bunching occurs, a build up of compressive longitudinal forces in the rail, sufficient to cause a misalignment, can occur over a short distance. Undertaking track work that breaks the bond between the sleepers and ballast can result in localised creep and bunching of rail. The current approach to creep measurement, that is, monitoring rail movement every 500 m, may not detect these localised variations.
Safety Advosory Notice
The Australian Transport Safety Bureau advises that all track maintainers in Australia should consider the implications of this safety issue and take action where considered appropriate.