Green motorways. Contradiction in terms or potential reality?

This article was first published in Sourceable

A few years ago I was stuck in hellish Sydney traffic, with the temperature soaring close to 40oC, and as I entered the tunnel surrounded by huge walls of concrete, pollution and heat haze and I suddenly thought, ‘this is a great place for plants’.

It sounds crazy, but the right plants combined with the right technology could do wonders for this harsh urban infrastructure, and I believe that science, investment and pure necessity are all at the perfect meeting point to make it viable, and I would argue essential, to turn it green or into what I like to call ‘living infrastructure’.

Soon after this traffic experience I started seeing opportunities for living infrastructure everywhere. Catching the train I looked out the window and saw massive amounts of unused, dirty harsh spaces along railway lines. On the bus I could see roads, bus shelters and highway overpasses – no end of blank, harsh, ugly environments that could benefit from plants and be transformed into active living infrastructure in the truest sense.

Travel around Australia and it’s clear to see we’re in the midst of an infrastructure boom. The federal government has allocated $50 billion to infrastructure, and NSW alone is in the midst of a $20 billion infrastructure spending program.

The question is – how much of that infrastructure investment will be in living infrastructure and what difference would plants and technology make to those environments?

img integrating plants into infrastructure projects

What if we integrated plants and even art into infrastructure projects? (Concept image by Junglefy)

1. From heat island to green sink

image of Atlanta Georgia showing heat island effect

On May 11-12, 1997, NASA used a specially outfitted Lear Jet to collect thermal data on metropolitan Atlanta, Georgia. Nicknamed ‘Hot-Lanta’ by some of its residents, the city saw daytime air temperatures of only about 26.7 0C on those days, but some of its surface temperatures soared to 47.8 0C. (Image courtesy NASA/Goddard Space Flight Center Scientific Visualization Studio via Wikimedia Commons.)

Have you ever seen those shots taken by thermal imaging cameras of a city environment on a hot day? Hard surfaces like concrete and bitumen reflect a lot of heat, making a hot day even worse and having an impact on the temperature of a city as a whole – it’s something known as the urban heat island effect. 

Heatwaves have the power to kill; for example, during the 2003 heatwave in Europe, 70,000 additional deaths were recorded, (making it one of the region’s deadliest natural disasters of the last 100 years) and in Australia extreme heat events have been responsible for more than the combined total of deaths from all other natural hazards. This becomes particularly concerning when you consider that the urban heat island effect makes city dwellers even more vulnerable to the dangerous effects of extreme weather events like this.

The challenge is that much of our existing city infrastructure is lined with concrete (think sound barriers, tunnels, bridges, tunnel entrances) and bitumen with little to know vegetation. All of these surfaces reflect the heat and as such they serve to exacerbate the urban heat island effect across a city sending temperatures to unbearable levels. In Australian cities, this is particularly concerning.

But what if we flipped it? What if we turned these hard, reflective surfaces into living walls, rather than concrete ones? What if we found ways to incorporate plants, whilst still ensureing the functionality required for such infrastructure? This would have a dramatic effect on the temperature of these environments – making it better for people using them, and also reducing the heat reflection returning to the city.

2. From exhausts to air filters

According to the World Health Organisation (WHO) air pollution is now the world’s largest single environmental health risk with some 3 million deaths a year linked to exposure to outdoor air pollution.

You don’t have to be a rocket scientist to realise that motorways carry a lot of vehicles, and vehicles equal pollution. The harsh environments surrounding these places do nothing to reduce that pollution – instead they basically collect and intensify it, and then when it rains, this runs off into storm water.

What if we lined our motorway tunnels with plants? (Sounds crazy, but its possible. These environments are lit, and there are numerous plants that could survive in these environments). Better still, what if we lined the tunnel extractors with plants? Those plants could then naturally clean the air before it enters the surrounding atmosphere. And then what about the harsh environments surrounding roads, rail, bridges and carparks? What if these became the green lungs of the city? Sucking up the pollution, cleaning the air, filtering and even harvesting and using storm water?

What if we went from this:

image of Sydney motorway with traditional sound barrier

Existing Sydney motorway with traditional sound barriers.

To this:

image showing Sydney motorway concept showing living wall replacing traditional sound barrier

Concept visionalisation of the same motorway with a living wall


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