Measuring the network

ARRB’s ‘one-stop-shop’ in pavement strength testing – its Traffic Speed Deflectometer – is helping gather important information about Australia’s expansive road network.When only 11 units of a product exist in the world, it certainly becomes a prized possession for the owner. Unlike a classic car, however, ARRB Group’s Traffic Speed Deflectometer (TSD) isn’t a collectible.

The pavement strength testing unit is one of 11 manufactured by Danish company Greenwood Engineering so far, and it’s been put through the hard yards over a short period.

“We’ve basically run with it on the road for about two and half years and it’s been doing great things,” says Richard Wix, Principal Consultant at ARRB.

The unit was the eighth TSD to be delivered in the world, with previous systems operating in Denmark, the UK, Italy, Poland, China, South Africa and the US.

The TSD was originally brought over to Australia on a trial basis for Roads and Maritime Services and the Queensland Department of Transport and Main Roads in 2010. ARRB was involved in the process and quickly jumped on the opportunity to bring a unit to the country on a permanent basis.

Since 2014, ARRB’s TSD has been gaining traction in data collection on Australia and New Zealand’s road networks. It has travelled over 240,000 kilometres and collected crucial data on more than 100,000 kilometres of that distance.

“The basic concept of the TSD is that it’s a detector for assessing the bearing capacity or strength of the road network. It does that by applying a weight to the pavement and measures the deflection velocity of the pavement under that load,” explains Mr. Wix. “Once we have that information, we can process and calculate the deflections in the road.” The system utilises doppler lasers to monitor the response of a pavement to the application of a mass. The high accuracy and resolution of the unit allows engineers to pinpoint areas where the pavement may be subject to failure.

The TSD measures continuously and reports every 10 metres. It needs two operators: one to drive and the other to run the pavement collection systems.

“We can typically cover more than 250 kilometres in a day, compared with less than five kilometres typically achieved using traditional methods at the same 10-metre reporting interval,” says Mr. Wix. The TSD can travel at speeds of up to 90 kilometres per hour while scanning, which eliminates the need to disrupt traffic during the information-gathering process.

As well as being safe it is also more cost-efficient, as no traffic control is required.

Mr. Wix asserts that the TSD helps fill a gap in knowledge when it comes to the state of the nation’s road network, especially in the more remote rural areas and on arterial routes. “It drives around the country gathering so much of this data, which you can’t get elsewhere,” he says.

In the past, the task of measuring the breadth of Australia’s road network has been seen as impractical, especially given the fact Australia has the ninth largest road network in the world.

Since receiving the TSD, ARRB has made some additions of its own to the system. The unit is now fully integrated into ARRB’s Hawkeye platform. Additional Hawkeye sensors are fitted to the TSD to measure the functional performance of the pavement, including roughness, rutting, texture and automated cracking, with a number of extra cameras mounted on the vehicle to help collect images.

The Hawkeye processing and viewing software fully synchronises all of these data streams, ensuring that structural and surface condition measurements are time-stamped and measured simultaneously.

Mr. Wix says another potential addition to the TSD system that ARRB may look at is a ground penetrating radar to extensively evaluate the health of the pavement below the surface. As he puts it, the TSD provides a comprehensive “one-stop-shop” for assessing the structural and functional performance of the pavement, which has opened up a lot of doors for developing Australia’s road network and identifying areas that need attention.

“It might be used for determining heavy vehicle routes, optimising the freight network in certain areas and general maintenance,” explains Mr. Wix.

He says the collected data may eventually be used for other applications in the future, including major projects and 3D models.

ARRB is also involved in one of the TSDs deployed overseas. It operates one in the US under ARRB Group Inc and has fitted out a unit in South Africa for a company in Durban with Hawkeye sensors.

Road authorities in Queensland and New South Wales and the New Zealand Transport Agency have taken advantage of its capabilities and Mr. Wix says other state agencies are coming on board seeking to reap the benefits of the technology. The only issue now is that the TSD’s schedule is busy with projects across the country.

Mr. Wix says that the company is now seriously considering bringing a second unit to Australia to meet demand. “It’s a pretty special piece of equipment for Australia to have. It’s growing technology in the marketplace,” he says.

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