Greening project transforms road barriers to reduce car pollution

Greening project transforms road barriers to reduce car pollution

Road barriers could be retrofitted with “ecological buffers” to cut air and noise pollution, as part of an innovative greening proposal from RMIT researchers.

New air pollution modelling suggests vehicle emissions along mega-projects such as the North East Link, Monash Freeway and Eastern Freeway will exceed Victoria’s new air pollution standards by 2036, creating poor air quality in the surrounding areas.

To help protect both local residents and drivers from noise and air pollution, RMIT School of Design academics and industry partners are proposing “ecological buffers” using vertical gardens and green walls to improve noise and air pollution, as part of their new project Transforming Melbourne Motorways’ Noise Barriers.

RMIT architect and sustainability lecturer Nadine Samaha says existing motorways use concrete and steel columns, which can reduce noise but make no impact on air quality - a particular problem for residents near major roads.

“Motorway air pollution can have a significant effect on the health of residents living nearby,” says Samaha, from Level Architekture and the RMIT Urban Futures Enabling Capability Platform.

“75% of Melbourne’s air pollution is caused by vehicle emissions which carry harmful chemicals that can have devastating health impacts including cardiac arrest, low birthweight, asthma and reduced lung function in children.

“According to the Australian Institute of Health and Welfare, more than 3000 Australians die early from urban air pollution each year – more than the national road toll.

“Our project proposes to retrofit and transform Melbourne’s motorways by creating ecological buffers to address noise and air pollution, while improving liveability and protecting residents from urban heat island effects, notoriously affiliated with asphalted roads and concrete barriers.”

Reducing air pollution

The most common pollutants emitted by vehicles are carbon monoxide, carbon dioxide, nitrous oxide, ozone and particulate. These air pollutants also contribute to climate change.

To reduce air pollution on Melbourne motorways, the project integrates a combination of vertical greening, green walls and rain gardens to absorb some of the motorway’s vehicle emissions.

Proposed ecological barrier view from service road. Proposed ecological barrier view from service road.

“A study conducted by the University of Surrey found just having trees besides roads is not enough to reduce air pollution,” Samaha says.

“This is because the tree canopy is often too high to provide a barrier or filter for road-level tailpipe emissions.

“They found the most effective way for improving air quality, reducing pollution exposure and cutting back carbon by up to 63%  is to plant dense green infrastructure hedges or a combination with trees.”

Reducing noise pollution

Current methods of reducing motorway noise are focused on noise wall construction, says project co-designer Dr Jordan Lacey from the RMIT School of Design and RMIT Urban Futures ECP.

However there is always residual noise that impacts on the wellbeing of residents living nearby motorways, Lacey says.

“By integrating sound capturing systems of residual noise with microphones we can change the typical noise heard on highways into something more melodic,” he says.

“This process, known as noise transformation, captures residual noise which is then fed back through a computer-based algorithm and played back through a speaker array to mix with environmental sounds.

Schematic of the proposed noise barrier. Schematic of the proposed noise barrier.

 Lacey has successfully applied this concept with a research team, including Professor Sarah Pink from the Emerging Technologies Research Lab at Monash University and Associate  Professor Lawrence Harvey from SIAL Sound Studios at RMIT, with an Innovation Grant from Transurban.

“To contain noise further, we suggest curving the noise barriers structure at the top to reflect the noise back onto the motorway, further reducing sounds from spreading to surrounding suburbs,” he says.

“Combining these modifications with the noise transformation effects should significantly reduce noise pollution and improve motorway environments in urban centres.”

With the designs proposed in Transforming Melbourne Motorways’ Noise Barriers, Samaha hopes the project can further create a greater connection between people and the natural environment for healthier and liveable cities.

“Cleaner and greener spaces with reduced noise and air pollution, may see further health benefits for residents living nearby,” she says.

“It may also encourage a healthier and more active lifestyle.”

The Transforming Melbourne Motorways’ Noise Barriers project team is currently looking for partners to trial and implement the proposal. Contact the team.


Story: Chanel Koeleman


  • Sustainability
  • Design
  • Urban Design
  • Research
  • Environment

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RMIT University acknowledges the people of the Woi wurrung and Boon wurrung language groups of the eastern Kulin Nation on whose unceded lands we conduct the business of the University. RMIT University respectfully acknowledges their Ancestors and Elders, past and present. RMIT also acknowledges the Traditional Custodians and their Ancestors of the lands and waters across Australia where we conduct our business - Artwork 'Luwaytini' by Mark Cleaver, Palawa.