Photographs of the reconstructed piece of track near Bates, released by the Australian Transport Safety Bureau, show how the cracked line failed after a fully-loaded freight train passed over it.

Crash investigators who checked an ultrasonic scan of the track taken three days earlier found it had a near-2cm crack, which meant it should have been replaced.

Rail authorities operating routes other than the Adelaide to Darwin railway, have now been told by the RTSB to introduce a new software back-up system which will double-check manual track scanning.

After the Bates derailment in April 2008, the software system found 100 similar serious cracks had been missed in other locations by manual operators who drive modified 4WDs along country railway lines every seven days.

All have been fixed, while the 20-month long investigation took place and interim safety measures were also put in place during the inquiry into the Bates accident – the second in the same location in a year.

Central Queensland University Professor of Rail Engineering, Gopi Chattopadhyay said metal fatigue was an increasing problem in rail lines because of heavier loads to create better productivity.

He said experts wanted to triple-check test results in the future.

This month, the Australian Transport Safety Bureau issued a bolt hole crack safety advisory notice to the Australian Rail Track Corporation.

“The process for identifying potential rail defects is limited by the ultrasonic test vehicle operator’s ability to detect and assess the echo patterns correctly,” it found.

Before the report’s release last month, the ATSB had also changed rules which did not require damaged lines to be replaced until cracks reached 2cm.

All flawed lines now have to be replaced, an attempt to tackle the increasing problem of so-called “bolt-hole cracks”.

The cracks begin at the edges of holes in sections of rail line which accommodated bolted plates to join two rails together.

Many of the plates have since been removed and the lines welded together, leaving the holes weakened.

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The locomotive operated by Genesee and Wyoming was towing 23 carriages laden with limestone from Penrice Soda’s Angaston quarry when it came unstuck just after 1pm near Penfold’s Barossa Valley headquarters.

The accident blocked traffic through the town as carriages balanced dangerously close to houses which backed onto the train line.

The train, carrying a driver and observer, was delivering the limestone to Penrice Soda’s Osborne processing plant.

Genesee and Wyoming general manager operations Ian Hall said 11 carriages derailed but that nobody was injured.

The company contracts Transfield to maintain the tracks, but Mr Hall said it was too early to speculate as to the cause of the derailment.

He said the tracks were inspected on a regular basis and that there had been “no warning” to problems at the bend.

“At this stage we still don’t know what the cause of the derailment was and we probably won’t for another 24 to 48 hours,” he said.

“We expect to have recovery (of the train) within the next 18 to 24 hours and have the line back in full operation by tomorrow afternoon.”

He said the train was travelling at 20km/h at the time of the incident.

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