Department to work with asphalt association on recommendations
The report into one of north Queensland’s melting roads has led to Department of Transport and Main Roads (TMR) being tasked to ensure they don’t occur again.
The review centres on repairs the Millaa Millaa-Malanda Road and nearby highways in the Atherton Tablelands, though newly paved routes further south elsewhere in the state and interstate have also been reported
According to the Queensland government, the report found a variety of factors contributed to recent sealing issues including the makeup of the road surfacing material, atmospheric conditions, and traffic management.
Read how TMR tackled the melting roads issue when it surfaced, here
Transport and main roads minister Mark Bailey says the events that led to multiple vehicles being damaged, including commercial vehicles, were unacceptable and he had given firm instruction to the Department of Transport and Main Roads that it could not happen again.
“As soon as I became aware of this matter I contacted my director general,” Bailey says.
“Now that we have this report showing what led to the issue, I don’t expect to see similar incidents around the state.
“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.”
The investigation was undertaken by an independent expert, in consultation with the Department of Transport and Main Roads (TMR) and its contractor, COLAS.
“The report concludes the issue was caused by a number of different factors, including spray seal rates, spray seal mix, aggregate size, variable underlying surface texture and higher levels of moisture,” Bailey says in explaing what happened.
“The report also identified that the road was affected, in part, due to traffic management during brooming of aggregate that had come loose.
“Traffic management on the day allowed south bound vehicles to stop on exposed binder where stripping of aggregate had occurred.
“During this time, vehicle tyres became stuck to the exposed binder and this contributed to the seal binder lifting.”
Bailey says the design and application of road seals is “a complex and technical process” noting that 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.
“The department works alongside AAPA and will look at the recommendations from the investigation through its existing strategic alliance,” he adds.
“We have now developed and circulated additional guidance for immediate implementation to help manage seal risks.
“TMR will look closely at the recommendations and learnings from the independent report to determine what additional steps may be needed to ensure this 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.
“We may also conduct research into the risk associated with sealing in a range of challenging conditions with the Australian Road Research Board.”
TMR is hosting detailed spray sealing workshops across Queensland, that are open to both departmental and external participants. To registration details can be found here.