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Main Roads WA approached Oz Rumble to investigate the suitability of a European or US-style milled-in audio tactile treatment instead of the unsuitable conventional raised treatment. Oz Rumble had recently developed milled rumble equipment for use in Australia, and having recently trialled this equipment with Transport for New South Wales, it was the perfect time to try a permanent, milled-in audio tactile system in WA.

The Problem
Main Roads WA is the main transport agency of the Western Australian government, and is responsible for managing one of the most expansive road networks in the world. In the northern end of Western Australia is the Pilbara region – encompassing 25% of the State and some 3000 kilometres of road and highway assets supporting the Pilbara Port Authority, the largest bulk port authority in the world! Suffice to say, the road network in the Pilbara is high-volume, heavy weight and hard wearing. 

Main Roads WA is committed to providing improved delineation and safety initiatives across the extensive rural road network in the Pilbara, and audio tactile treatments are a critical part of that. Audio tactile treatments are proven to be a cost effective method of preventing run-off road accidents and reducing pavement maintenance. 

Unfortunately, conventional raised audio-tactile treatments have proven ineffective in the Pilbara, with all that heavy traffic leading to a greatly reduced rumble strip lifespan! The high axle loads place enormous wear on pavement markings, which means any form of raised marking is quickly crushed into the pavement surface. Plus, all conventional audio-tactile treatments involve a raised profile in either a thermoplastic or cold applied plastic material, which is incompatible with the high ambient temperatures throughout much of the year in the Pilbara. As such, the task of building and maintaining a road network safe and appropriate for mining, industrial and tourist traffic is particularly challenging. Luckily, Oz Rumble was up to the challenge. 

 

The Solution
Main Roads WA approached Oz Rumble to investigate the suitability of a European or US-style milled-in audio tactile treatment instead of the unsuitable conventional raised treatment. Oz Rumble had recently developed milled rumble equipment for use in Australia, and having recently trialled this equipment with Transport for New South Wales, it was the perfect time to try a permanent, milled-in audio tactile system in WA.

Since Main Roads were already in the process of delivering a broadscale shoulder upgrade program in the Pilbara, Oz Rumble was able to work the new treatment into their existing roadworks. This was done in association with our established partner business, Retex Pavement Services.

As an audible road treatment specialist, we were in our element on this project. Our solution was to provide our Australian-first milled audible treatments – because they last as long as a road does, saving time and money on reapplication costs! With Oz Rumble’s patented technology, Main Roads WA received a treatment that would be able to withstand intermittent resurfacing plus water and debris build-up, ensuring prolonged driver safety and the effective mitigation of single-vehicle runoff incidents. 

Implementation
Oz Rumble deployed three specially-designed items of plant to execute the works – including a large Rumbler 6200HD and two skid steer-mounted SSR Rumblers. Each unit was calibrated to deliver the required spacing and depth of cut, allowing us to install the strip at an average rate of one kilometer per hour.

The 200mm wide treatment was trialled at both 610mm spacing and 305mm spacing, and was installed at a specified profile depth of 14mm. Substrate types varied from new dense grade asphalts to single and multi-coat sprayseals. 

We installed the milled-in rumble strip along 680 kilometres of edge line treatment across the Pilbara, including at sites on the Great Northern Highway, Tom Price Road and Point Samson Road. A small three kilometre section of centre line was also installed for assessment.

Despite the ongoing constraints of COVID-19, Oz Rumble was able to assemble the team and resources to deliver the project within the client’s operating window. Our works were also completed neatly within the client’s existing project – we installed the milled-in rumble treatment immediately after the completion of the asphalt shoulder upgrade and before the sprayseal overlay was performed.

Outcome
As the Oz Rumble milled-in rumble strip is the only inset audio-tactile delineation treatment currently available in Australia, this trial was the first broadscale application in the country. The trial areas now mirror what is a standardised treatment of all state and federal highways in the United States.

Overall, the treatment was installed successfully and the consistency of the finish was noted by Main Roads WA – plus, initial feedback from other professional road using groups has been broadly positive. 

The Main Roads WA Road Safety Division is currently conducting and monitoring the trial performance, and the team at Oz Rumble anticipate hearing about the improved outcome when the data is available. If the Oz Rumble milled-in rumble strip outperforms the conventional method as expected, we’ll be able to call the project a roaring success.

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Audible treatments for the life of your road