A review into a Far North Queensland road which had caused damage to vehicles and caused community chaos has found that a variety of factors contributed to the roads sealing.
Millaa Millaa-Malanda Road was closed for emergency repairs in July after several vehicles’ tyres became stuck to the exposed binder, which also contributed to it lifting.
The report states the issue was caused by a number of factors, including spray seal rates, spray seal mix, aggregate size, variable underlying surface texture and higher levels of moisture.
Traffic management also played a part in the road failure, as south bound vehicles were allowed to stop on exposed binder where stripping of aggregate had occurred.
Queensland Transport and Main Roads Minister Mark Bailey said the events that led to multiple vehicles being damaged were unacceptable, and he had given firm instruction to the Department of Transport and Main Roads that it could not happen again.
“A separate resealing issue that occurred near Marlborough on the Bruce Highway several weeks later remains under review, and it is still too early to say if the two conditions were comparable,” Mr Bailey said.
An investigation was undertaken by an independent expert, in consultation with the Department of Transport and Main Roads (TMR) and its contractor COLAS.
“TMR requires all seal designs to be undertaken by designers who have completed the Australian Asphalt Pavement Association (AAPA) Sprayed Sealing Selection and design course,” Mr Bailey said.
“The department works alongside AAPA and will look at the recommendations from the investigation through its existing strategic alliance.
“We have now developed and circulated additional guidance for immediate implementation to help manage seal risks,” he said.
Mr Bailey says TMR will look closely at the recommendations from the report to determine what additional steps may be needed to ensure this incident does not happen again.
“Measures may include updating TMR’s specifications, increasing the use of crumb rubber (recycled tyres) in seals and introducing a registration or similar system for contractors,” Mr Bailey said.
“We may also conduct research into the risk associated with sealing in a range of challenging conditions with the Australian Road Research Board.”
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