Engineering, Environment and Sustainability, Products & Resources, Products & Technology, Track & Civil Construction

The sustainable sleeper

An innovative railway sleeper made from recycled plastics was recently granted type-approval by V/Line. With mainline trials completed or near completion and other rail companies interested, this is an exciting and innovative development in the future of sustainable rail infrastructure.

An Australian company has been working on an innovative development bringing a new, sustainable approach to the rail industry

Duratrack, a new recycled plastic railway sleeper, is more resilient than timber, lighter and less carbon intensive than concrete. A significant milestone has now been reached with V/Line and MTM granting type approval to Integrated Recycling’s new sleeper.

General manager of Integrated Recycling Stephen Webster believes this will revolutionise this aspect of rail infrastructure. Webster is clear on the benefits of the Duratrack sleeper: firstly, it uses plastics that might otherwise form pollutants or at least take decades to breakdown in landfills. The sleeper also lasts longer than a timber sleeper which is vulnerable to environmental degradation. Duratrack is easy to use, weighs the same as timber and utilises existing rail equipment. When compared with concrete sleepers, it is significantly lighter and produces less CO2 emissions during production.

The Duratrack sleeper is an exemplar product for rail to help meet the targets being set by each government for the use of recycled products under the National Waste Policy Action Plan.

A recent PWC report says the Australian economy could enjoy a boost worth nearly $2 trillion in the next 20 years if the nation abandons its “take, make, use, waste” approach to materials and resources. There is a huge benefit to the Australian economy if Australia can embrace products from the “circular economy,” using finite resources such as end of life plastic for innovative new purposes and regeneration.

Integrated Recycling is part of the Pro-Pac Packaging group, a sustainable and innovative packaging company based in Melbourne. With a production facility in Mildura, Integrated Recycling makes a range of parkscape and other products from recycled plastics including bollards, outdoor furniture and retaining walls.  Around five years ago, the company started developing plastic sleepers which have evolved through extensive trials and testing to become Duratrack.

A long-lasting product

Webster said durability was the key to Duratrack’s success. “What we’re doing is harnessing the inherent characteristics of plastic to give us the longevity and durability that is needed for rail infrastructure,” he said.

While the product already has been used to replace concrete sleepers, its initial development is as an alternative to timber railway sleepers.

“A disadvantage of timber is that it degrades as soon as it is cut due to pests, water or other environmental effects,” Webster said. “The longevity of plastic, and the fact that it can be engineered to meet specific requirements of the rail industry, makes these sleepers a highly attractive alternative to conventional wooden sleepers. And this brings the rail industry into the circular economy.”

Tested in harsh climates

But could the Duratrack sleeper be impacted by extreme conditions, particularly the unrelenting sun and heat in Australia’s interior? Webster says that the Duratrack sleeper and other products made by Integrated Recycling have been extensively tested in Australia’s harshest and hottest desert regions; in high saline marine environments and in the Queensland sub-tropics. None of these have had an adverse effect on the plastic.

Duratrack is made from a patented formulation to meet the performance requirements of the rail environment. A unique aspect of that formulation is the use of flexible as well as rigid plastics. Polyethylene and polystyrene are the two types of recycled plastics used in the sleeper’s formulation. Both plastics are used in many agricultural applications around Mildura, such as table grape vine covers, irrigation pipes and fruit boxes. At the end of their primary lives, these products provide an important source of waste plastics for re-purposing. As volume and demand increases, Integrated will draw in plastics from wider areas.

In-track trials

The Duratrack sleeper has undergone extensive in-track trials with QR, MTM, V/Line and ARTC, as well as laboratory testing and analysis with the Institute of Railway Technology at Monash University (Monash IRT). It meets the requirements of the new Australian Standard (AS1085 part 22) for alternative material sleepers.

A substantial trial with Metro Trains Melbourne, saw around 200 broad gauge Duratrack sleepers installed on the bridge deck over Punt Road at Richmond Station. The sleepers were installed in mid-2019 and since then about 8.3m gross metric tonnes passes over the sleepers each year. “That trial was successfully conducted and MTM awarded Duratrack type approval in April 2021 following V/Line’s type approval in March 2021,” Webster said.

Further north, Queensland Rail has conducted another extensive 18-month trial of the narrow-gauge version of the Duratrack sleeper. That trial on two coal freight lines concluded after approximately 4.5m gross metric tonnes of freight passed over each trial site. QR is currently validating the installation procedure for the Duratrack sleeper with further testing and analysis conducted by Monash IRT.

ARTC and Monash IRT are currently undertaking a research, development and demonstration project funded by Sustainability Victoria at Tottenham Junction in Melbourne’s west. Here Duratrack standard gauge sleepers have replaced timber sleepers on a through road, with trains travelling up to 80kph. Several sleepers are instrumented to provide live load data for analysis and validation of their laboratory testing. As part of the project, a noise and vibration comparison test will be conducted with nearby concrete sleepers to determine the extent of noise and vibration attenuation from the Duratrack sleepers. The analysis of the live load data will provide significant insight into the in-track performance of the sleepers and to date the results are very positive.

Product development

Webster notes how the concept has progressed. “The plastic sleeper was started back in 2015 at a time when there were no standards for alternate material sleepers,” he said.

“Monash IRT were asked by Public Transport Victoria to write a guideline for the design and testing of plastic sleepers in the tourist and heritage sector which was a great starting point. At the same time Sustainability Victoria funded a Monash University R&D project on the use of flexible plastics in railway sleepers. The resulting paper had significant influence in the sleeper’s acceptance by mainline rail operators and Sustainability Victoria’s continued involvement has played a vital role in the development of Duratrack.

“The first-generation sleeper was made and installed in 2015 at several tourist and heritage railways in Victoria for monitoring and where they remain today. The sleepers were also successfully tested by Monash IRT in the lab against those guidelines in 2017,” he said.

Webster continued: “Most significant are the mainline in-track trials conducted by the major railways: QR, MTM, V/Line and ARTC which have provided independent assessment by the engineers from those accredited rail operators.

“It is not just our advocacy that is progressing Duratrack, it is the performance of the Duratrack sleeper that is satisfying the requirements of the rail operators,” he said.

The way ahead

Webster believes they are now in position to really grow their market. “Now that we have been validated independently, we are looking very closely at building the first stage of an upgradable Duratrack production line that can increase as demand increases,” he said. “Up until now we have been making sleepers in trial quantities only.”

Waste plastic is a global problem and circular economy products like the Duratrack sleeper are a part of the solution. This ingenious Australian invention has the ambition to internationalise rapidly with a focus on Asia through awarding licences to use the IP to produce the sleeper locally.

Webster says, “We think there is cause for genuine optimism that this product can be a winner for both the rail industry and the environment”.


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