Queensland’s Department of Transport and Main Roads has partnered with the Australian Road and Research Board (ARRB) to research and develop solutions for improving the state’s roads and pavements. Here, Transport and Main Roads Director General Neil Scales runs us through some of the major developments occurring on our roads.  

Queensland’s Department of Transport and Main Roads (TMR) invests billions of dollars annually building and maintaining the state’s road and transport network. Transport and Main Roads Director General, Neil Scales, said finding new and innovative approaches to our infrastructure was critical to investing this money wisely.

“The more frequent extreme weather events we are encountering, such as flooding, means our roads infrastructure needs to be built to be more resilient,” Mr Scales said.

“Ensuring we get the best value for money, long term, out of every dollar invested is critical to delivering a network that serves the needs of Queenslanders now and in the future.

“To do this we have developed a structured research and development program to help us deliver excellence and achieve real savings.

“Through our partnership with the Australian Road and Research Board (ARRB), we have developed a National Asset Centre of Excellence (NACoE) to undertake targeted research and deliver practical applications of technologies that will deliver value for Queenslanders.”

Now in its fifth year, the NACoE was established to improve the specialist capability and capacity of both TMR and ARRB Group through a sustained, collaborative program of challenging projects which unlock innovation and deliver superior technology and road transport solutions.

The program is diverse but has a strong focus on pavements, asset management and structures research. It targets international best practice, providing guidance to reduce excessive conservatism and allow the use of innovative materials, and translating new knowledge into best practice.

“We invest more than $4 million each year in this program and it is already delivering important innovations and significant savings,” Mr Scales said.

“We have already achieved outstanding outcomes in the areas of cost saving and performance, sustainability, safety, and reliability.”

Savings and performance: EME2

Mr Scales said the most significant return TMR had seen from the program was the wider use of high modulus asphalt, or EME2.

“Developed in France in the early 1990s, EME2 has been used extensively in Europe on busy roads and airports with outstanding success,” Mr Scales said.

Compared to ‘conventional’ asphalt, EME2 offers superior performance, 20-25 per cent thinner bases and improved productivity in construction. Time savings of 30-50 per cent have been reported in the construction of thick asphalt sections including EME2.

“During the past four years, TMR and ARRB have been engaged in an effort to transfer EME2 asphalt technology to Australia,” Mr Scales said.

In 2017, about 10,000 tonnes of EME2 was successfully placed on the Deagon Deviation as part of the Gateway Upgrade North project — at the time, the largest use of EME2 in Australia — and about 6500 tonnes was used in a pavement rehabilitation (inlay) project on Gympie Road.

More recently, 53,000 tonnes of the asphalt was placed on the Port Drive Upgrade project, and about 9000 tonnes on a pavement rehabilitation project on Steve Irwin Way on Queensland’s Sunshine Coast.

“Each year TMR spends about $100 million on asphalt, so the wider use of EME2 has huge potential for savings, as well as improved performance on highly trafficked roads,” Mr Scales said.

Foamed bitumen stabilisation is offering huge benefits.

Sustainability: Crumb rubber modified binder

The focus of NACoE’s research is not limited to cost and performance, however, with sustainability another major driver.

NACoE’s Crumb Rubber Modified (CRM) binder project, which aims to promote the use of recycled rubber from used car tyres into asphalt and surfacings, has already made significant advancements for the sustainability of Queensland’s road network.

“Recycling old tyres into roads is a win for our environment, our budgets and our road network,” Mr Scales said.

“Road surfacing containing CRM binder lasts longer than those using conventional bituminous binders, and show better durability and waterproofing.

“The use of CRM binder on resurfacing projects in 2015/16 and 2016/17 diverted around 200,000 tyres from landfill, and saved almost $170,000.”

NACoE has successfully delivered CRM demonstration projects in both sprayed seals and in open graded asphalt – these projects are being monitored for long-term performance as part of the program.

While further demonstration projects are required before the widespread use of CRM binder in open and gap graded asphalt, updates to the department’s technical specifications to increase the use of CRM binders in sprayed seals have now been implemented.

Safety: Wide centreline treatment

Safety is the number one priority for TMR, and NACoE resources are being put to work in this area.

After an extensive evaluation as part of the NACoE program, wide centreline treatment has now been installed on more than 1000km of Queensland roads.

This one-metre spaced line-marking between opposing lanes provides additional clearance between oncoming vehicles, while maintaining safe opportunities to overtake. The treatment can be supplemented with audio tactile line markings to provide additional safety benefits, particularly on routes where drivers are likely to become fatigued.

A trial section of the Bruce Highway combining the wide centreline treatment with audio-tactile markings has seen a 43 per cent reduction in cross median crash rates.

This research has led to an economical method to maximise the existing road network and achieve significant improvements in road safety.  

Durability: Foamed bitumen stabilisation

“Where durability is concerned in areas that flood, foamed bitumen stabilisation is offering huge benefits,” Mr Scales said.

“NACoE is helping us convert the foamed bitumen research outcomes from the past four years into technical notes incorporating all learnings, and where appropriate, to help improve specifications.”

Foamed bitumen is formed by injecting a small quantity of cold water into hot bitumen to produce an instant expansion. In this foamed state, bitumen is highly efficient at wetting and coating the finer particles of the pavement material, forming a mortar and binding the mixture together.

This process produces a pavement that is more resilient to flooding and uses less bitumen than asphalt concrete (2.5-3 per cent by weight compared to 4.2-6 per cent). It also allows for the use of lower quality aggregates, leading to significant savings.

In addition, foamed bitumen pavements exhibit superior fatigue properties compared to asphalt concrete, and significantly less shrinkage cracking compared to cement modified pavements.

Foamed bitumen offers excellent benefits for flood-prone areas and situations where inundation or extensive rain periods occur. It is also suitable where early trafficking is required as this is not achievable with layers of asphalt concrete due to heat retention issues.

Foamed bitumen is already being implemented in the coastal regions of Queensland, with TMR regions reporting an excellent success rate.

Crumb rubber modified binder promotes the use of recycled rubber from used car tyres into asphalt and surfacings.

Benefits in excess of the cost

NACoE’s achievements in its first five years demonstrate that TMR can, with confidence, achieve benefits far in excess of the costs from research and development.

Aside from the direct economic benefits of the research program, the ongoing transfer of technical capability, knowledge and technology between TMR and ARRB staff is a benefit that will mature as the program progresses.

“Working in partnership with industry, universities and other government bodies to leverage research, knowledge and resources – this is what NACoE and our broader agreement with ARRB is all about,” Mr Scales said.

“The synergy produced by working together is something that will help us to deliver excellence and better value for money for years to come.”

For more information on the NACoE program please visit www.nacoe.com.au.

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