Unused bolt-holes in the rail web are sufficient stress concentrators to result in the initiation and propagation of fatigue cracking, ultimately leading to the failure of the rail.
Action taken by the ARTC
The ARTC has introduced a common standard for bolt-hole crack limits across the whole ARTC network. The standard has lower thresholds for intervention.
ATSB assessment of response/action
Although the ARTC has addressed the risk of crack propagation in unused rail bolt-holes, the risk of crack initiation still exists under cyclic loading typical of actual rail traffic.
Safety Recommendation
The Australian Transport Safety Bureau recommends that the ARTC take further action to address this safety issue.