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Cool roads trial begins in Sydney

A cool road laid in Chippendale

By Cameron Jewell

17 June 2014 — An innovative project to lighten roads and battle the urban heat island effect has begun in the Sydney suburb of Chippendale, with a light concrete mix being spread over streets on Friday.

The City of Sydney trial, the brainchild of sustainability expert and The Fifth Estate contributor Michael Mobbs, is exploring how pale roads can reduce the microclimate of suburbs.

The urban heat island effect means cities can be a few degrees warmer than regional areas due to surfaces such as roads, footpaths and buildings absorbing heat from the sun. Using lighter-coloured materials has been shown to reduce the effect.

Data has shown that the temperature of roads in Chippendale – which account for 23 per cent of the suburb’s area – can be up to eight degrees higher than surrounding areas in summer, meaning discomfort and increased airconditioning costs for those in the area.

The trial will record temperatures across different locations across the suburb, including a 600-square-metre section of Myrtle Street that has just been covered in an open grade asphalt pavement filled with concrete slurry to create a lighter road.

Mr Mobbs told The Fifth Estate that the road where the trial was being carried out was “always, 24/7, year round, two degrees hotter than another road which is shaded by trees and buildings”.

Over the coming months, monitoring equipment will determine whether or not there is a reduction in ambient temperate along the paler pavement. Mr Mobbs said there was a temperature monitoring station on the streets already, so there would be very good before and after data.

He said he would also be measuring the effect lighter roads will have on nearby tree canopy, as darker roads had the effect of evaporating moisture from soil and stunting growth, increasing the urban heat island effect.

The project will complement research done overseas and provide some firm data on effectiveness and cost in the Australian context, Mr Mobbs said, hopefully leading to the project being expanded through Chippendale and other suburbs.

“The barrier to making cool roads the norm is lack of knowledge, lack of data and the lack of good costs and benefits data,” he said.

He hopes the trial will also help to reduce the cost of cool roads, which can be up to two to three times more expensive than traditional roads, until they were business as usual.

“With increased use and higher volumes the pale road will become cheaper. They last four times longer than bitumen.”

The project was featured on a recent Lateline episode on ABC, which Mr Mobbs said had garnered interest from councils, state governments and private sector operators across the country.

“What I think I’ve done, and my community has done, is put this on the national agenda,” Mr Mobbs told The Fifth Estate.

Sydney Lord Mayor Clover Moore said temperatures in Sydney were expected to rise in coming decades due to the city’s growth and the effects of climate change.

“Our cities are growing rapidly in size and population and our increasing energy consumption, carbon emissions and household waste is straining the natural environment,” Ms Moore said.

“The City is taking long-term action to tackle climate change. We are increasing the tree canopy by 50 per cent to cool buildings, reduce power bills and beautify our city, and making big investments in renewable energy. We will also continue to test new ideas to make sure we’re being as effective as possible.”

The cool road trial is one of four projects the City of Sydney is trialling from Mr Mobbs’ Sustainable Communities Plan, which shows how to make the suburb of Chippendale sustainable.

See here for further information.

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