Thinking

Four signs ahead for net zero roads in New Zealand and Australia

The vision of net zero carbon infrastructure could be one of the most significant contributing factors to a sustainable future that embraces the challenges of climate change.

As our cities grow and populations increase, the demand for our roads has grown with an increase in the number of private vehicles and higher demand for road freight resulting in a steady increase in emissions. In New Zealand, emissions from road transport increased by 100 per cent between 1990 and 2018. Australia is in a similar position with road transport contributing approximately 80 per cent of all transport emissions.

This is represented by both embodied emissions (direct emissions controlled during design, construction and operation) and enabled emissions (from road users). Ultimately, it’s all still greenhouse gas emissions and must be considered together when striving to meet international emissions reduction targets.

The climate doesn’t abide by defined categories so in order to truly decarbonise roads, total lifecycle greenhouse gas emissions should be represented, and tackled, holistically.

Figure 1: Where the embodied emissions and enabled emissions are in roads

The embodied emissions and enabled emissions are in roads

Roads are fundamental to the economic well-being of society which means the answer isn’t simply stripping them of all vehicles, rather it’s about focusing on how we use roads, and how to decarbonise them. This could be in combination with the decarbonisation of other forms of non-road transport such as public transport and mass freight.

Roads have been part of the fabric of human society for millennia, from trans-continental trade routes to local networks that connect communities to markets, and to the roads we see today performing many functions across every continent. Roads remain critical to carry the ‘heavy lifting’ of transit, enabling freight movements and bulk travel, especially in ‘last mile’ transport (the final leg of a journey in the movement of people or goods).

The decarbonisation journey may present challenges; however, with innovation and collaboration across the entire supply chain, including design, construction, maintenance and reuse/recycling, it may lead to a carbon friendly behaviour change by road users, owners and operators.

New Zealand and Australia both signed up to the United Nations Sustainable Development Goals (SDGs) and the Paris Agreement in 2015. The 2021 COP26 highlighted the global momentum for a transition away from fossil fuels. This accelerating pace of change, by reducing carbon emissions in road infrastructure, is a core aspect of the wider transport sector being able to contribute to these commitments.

This paper explores the four signs ahead for net zero roads in New Zealand and Australia:

1. Use roads differently

The most significant impact we can make in decarbonising roads lies in making better use of our existing networks, and where new roads are required, minimising their emissions. Roads are inherently material- and energy-intensive in their production, and today that also means they are carbon-intensive.

In the building new roads only encourages people to drive more, further increasing both congestion and emissions (with current vehicles). The Welsh Government has committed to building no new roads to respond to the climate emergency, and similar stances may start to be seen by more authorities around the world where populations are on the decline.

In New Zealand and Australia, we are still growing, and we have an opportunity to build greener roads.

The opportunity to reallocate space within existing road networks – shifting the way they are used and which mode of transport they support – places a greater emphasis on road corridors that maximise commuter efficiency, public and active transport, and decarbonised journeys.

In New Zealand, there’s a shift already underway in how the country uses its roads, with examples such as the Southwest Gateway Programme, Puhinui Interchange and Cameron Road Multi-Modal Upgrade, where space within existing corridors is being reallocated for public transport, walking and cycling.

In Australia, there is an integrated approach to active transport with cycling, walking and micro-mobility experiencing an unprecedented surge in popularity brought on by the COVID-19 pandemic.

Recently, Transport for NSW initiated Movement and Place, a cross-government framework for planning and managing roads across the state of New South Wales. It considers the whole road by addressing the needs of all users, including pedestrians, cyclists, delivery vehicles, private vehicles and public transport.

Aurecon developed the Cycleway Design Toolbox, one of the guides within the framework, to be used by practitioners, designers and evaluators. The design principles and recommendations aim to address the desired movement and place functions, and traffic speed and volume, of any location.

These kinds of changes and considerations are particularly important in densely populated city centres or urban settings where building wider or more roads to accommodate growth is simply not an option.

Speed specific road design

In reimagining existing roads, an eye must be kept on emerging technologies and the different ways roads will be used. We have already seen a rapid increase in the use of micro-mobility technologies, for example e-scooters, particularly in the past five years, and these forms of transport are likely to increase in usage.

The introduction of new modes of transport has the potential to better connect people with public transport and reduce reliance on private cars. They offer a unique benefit in enabling first-mile and last-mile transport movements for customers with closer point-to-point movements in a time-efficient manner.

Road authorities are continuing to plan on how to accommodate emerging micro-mobility technologies and other personal modes of travel into existing city road networks, with such varying speeds between different modes.

One solution is speed specific road design, where the corridor is divided up based on the speed a person travels rather than the mode they’re travelling with/on (Figure 2).

Figure 5: Street lane example widths for pedestrians, micromobility and higher-speed separation

Street lane example widths for pedestrians, micromobility and higher-speed separation

This approach delivers a multitude of benefits:

  • Reduction in enabled emissions (through less idling and improved traffic flow)
  • Movement quality for vulnerable users
  • Less conflicting interactions
  • Flow performance
  • Safety with physical and logical control by speed, space, etiquette and direction

This accounts for the rapidly changing way that transport is being used by people due to an increase in the use of electric vehicles and micro-mobility equipment, along with an increase in preference for walking and cycling in cities.

2. Reduce embodied emissions in design, construction and maintenance

The traditional practice of road construction and maintenance is inherently lean and efficient, a result of the economic benefits gained by minimising time, material use and material wastage. Early concepts for a ‘sustainable road’ emerged through both academic research and industry, primarily to optimise route alignment, reduce earthworks and material usage, speed up construction, and create safer and more integrated roads.

Roads are now entering a new chapter of sustainable construction and maintenance by aiming to reduce embodied emissions during their design, construction and maintenance, and initiatives are now being driven by government.

For example, the Draft Emissions Reduction Plan by the Ministry for the Environment in New Zealand proposes to mandate that energy use and embodied emissions are measured for all new projects, as well as improvement or maintenance contracts.

A decarbonised road from an embodied emissions perspective is:

  • Constructed using materials and processes that are net zero. This includes the extraction of materials, transportation of materials, manufacture of products and construction.
  • Designed to optimise the alignment (vertical and horizontal) to mitigate environmental impacts and reduce earthworks.
  • Resilient to future climate change impacts and materials (or labour) scarcity.
  • Designed in a manner that reduces maintenance demands and the requirement for future upgrades (including a reduction in labour spent, and material substitutions).
  • Designed to be adaptable to changing uses that respond to travel volumes, active transport, micro-mobility and new vehicle types (for example autonomous vehicles).
  • Able to support infrastructure that enables zero emissions operations and decarbonised transport modes (e.g. using renewable energy).
  • Readily amenable to recycling, reuse or repurposing at end of life.

Planners, designers, manufacturers and constructors have a role in ensuring that schemes are developed for their viability in terms of cost-effectiveness but also for their contribution to reducing carbon emissions in line with global targets.

Schemes that centre around energy and resource efficiency and optimisation, with materials and methodology innovations, together with the use of intelligent data will deliver the circular economy approach to the lifecycle of a road (Figure 3). It’s worth acknowledging that Europe has been using reclaimed asphalt in pavements for quite some time.

Figure 3: A circular economy approach to the lifecycle of a road

Circular economy approach to the lifecycle of a road

With the emergence of the circular economy approach to infrastructure design and delivery, there is currently a significant push for achieving the lowest upfront carbon reduction to address the immediate challenge of needing to decarbonise.

The risk is it may in fact lead to less durable materials or construction methods being chosen which has a significant impact on the ability to decarbonise a road’s maintenance or operations. On the flip side, future maintenance (including renewals which already occur) or replacement may be lower carbon in itself.

Considering the longevity and design of materials and methods used in road construction or upgrades, the maintenance, operation and disposal aspects must be considered today – a whole-of-lifecycle approach.

To examine these risks at the outset of a road infrastructure project will avoid wasteful end-of-life demolition, and wasteful labour time and material substitutions during operations.

International sustainability rating tools are becoming more prevalent in the design, construction and maintenance of roads to embed and record performance and measure improvements over time.

These provide a solid foundation, strong sustainability reporting, and effective narrative communication to move beyond simply achieving sustainability requirements toward meaningful outcomes.

Infrastructure assets are long-term investments with lasting impacts over multiple decades. It is vital to integrate sustainability into the development and delivery of projects to be able to tackle the global challenges of climate change in the future.

3. Reduce enabled emissions (from users of the road)

Road users that do not add further greenhouse gas emissions to the atmosphere are a significant part of the holistic decarbonisation of roads. The challenge is changing the way people and freight are moved to reduce the need for movement, while maintaining and improving living standards, especially for developing regions.

Decarbonisation isn’t defined by asset boundaries so road infrastructure must address all emissions across all influencing factors.

The following changes improve the emissions intensity of travel or reduce transport demand:

Transition to zero emissions vehicles

The transition to electric vehicles, and hydrogen-fuelled vehicles, across road networks is a critical initiative in reducing enabled emissions. Consumer desire for private electric vehicles is increasing, together with the commercial sector’s use of battery-technology light vehicles, and the start of hydrogen fuelled freight vehicles.

Uptake is expected to accelerate as the availability, performance, refuelling infrastructure, and economics of these technologies improves, in a virtuous circle. Other general vehicle advancement will continue to bring benefits – vehicle light-weighting, rolling resistance and aerodynamic improvements, for example.

Policy interventions to support electric vehicle sales and the early retirement of petrol and diesel engine vehicles will be required to substantially reduce enabled emissions in line with targets. For instance, New Zealand has seen a spike in the sale of electric vehicles in response to the introduction of the Clean Car Discount for consumers.

More efficient demand management

While the shift to zero emissions vehicles assists to decarbonise roads, it still equals congestion, and congestion will hinder the world’s achievement of the Paris Agreement target of limiting temperature rise to under 1.5 degrees.

Road design can influence user behaviour using green spaces, safety, convenience and reliability that provides easy and better choices other than the car. Emissions will be reduced in thriving cities and towns that integrate land use, urban development and transport infrastructure investments.

Quite often, a user’s travel behaviour is governed by their ‘path of least resistance’, which historically has been dominated by car travel. Roads can be designed in the future that address these factors and ensure that other modes of transport become the ‘path of least resistance’. This, in combination with policies that trigger changes in user behaviour, can contribute to reduced travel demand by car users.

Carbon emissions from freight also needs to be reduced. A significant way to reduce freight’s carbon footprint involves roads – the last mile of travel – the trucks and vans that carry goods from regional distribution hubs to local stores or homes. This is likely to rise as e-commerce (accelerated by the COVID-19 pandemic) increases the number of packages delivered to homes.

Another factor to reducing the total number of kilometres travelled by freight vehicles is using data intelligence and analytics to optimise fleet dispatch and routing, as well as the road network itself.

Governments that intervene with regulation will make it easier to reallocate road space for transport other than the car or light vehicle and create an expectation that this is a priority.

Optimising road network operations

New Zealand and Australia shouldn’t be afraid of a more interventionist approach to more actively managing demand on road networks, so that networks operate as efficiently as possible.

This may include road user charging in substitution for fuel duty. This topic is currently drawing criticism, however supporters are insisting that both a time-based charge and a distance charge would address both urban and rural motorists.

Optimising road networks includes how they interconnect with first and last mile travel. For instance, it may not be much good decarbonising a road if the final mile of a freight journey involves 20 diesel delivery trucks driving around inner-city neighbourhoods.

This is where an integrated solution is the answer – being strategic in placing infrastructure where it can be most convenient while most effective. This enables the continuous improvement and optimisation of movement efficiency and emissions reduction on road infrastructure.

Making streets healthy places

The concept of Healthy Streets, a human-centred framework for embedding public health in transport, public realm and planning, is a passive form of reducing carbon emissions for cities. The framework covers 10 indicators on the human experience needed on all streets, everywhere, for everyone.

Delivering city streets that change the lens of human experience through the Healthy Streets approach can drive change in transport and spatial planning in how streets look and feel.

In 2014, Transport for London won multiple awards for publishing the world’s first transport health action plan ‘Improving the health of Londoners’, which for the first time linked city and transport planning with emissions and human health; respiratory disease, safety (better access for pedestrians), and exercise for well-being.

Healthy Streets is now at the heart of the city’s policies with a new model that puts more emphasis on pedestrians, residents and businesses, with less emphasis on road transport.

The result is a more pedestrian friendly city, together with the introduction of an Ultra-Low Emission Zone in the centre of the city. Vehicles driving in the zone must meet tight emissions standards or pay the daily charge. This initiative is focused on improving breathing air quality for residents and visitors in the trial zone.

4. Make road infrastructure digital

A new role for the road

Roads already do an act of duty: carrying the lifeblood of economies, as conduits for emergency services and freight delivery, as carriers of essential utility infrastructure, and as links that connect people to work and each other. There is another role emerging; as a network of infrastructure providing renewable energy charging stations for battery electric vehicles (BEVs), together with hydrogen refuelling infrastructure for fuel cell electric vehicles (FCEVs).

Market analysts report that at least a quarter of charging (private vehicles) is likely to occur at work or through public electric vehicle charging infrastructure, and this is anticipated to be much higher for refuelling of hydrogen fuel cell vehicles.

Putting users and sustainability at the centre of road infrastructure

Digitisation has a vertical impact across the several layers of the road system. This brings new challenges and disruptions to the traditional approaches used in design, construction, management and operation; however, it also brings significant opportunities.

The road infrastructure that was traditionally the central element in the planning and management of road transport is shifting to the users and sustainability at the centre.

New roads can incorporate renewable energy in roadway lighting and intelligent management systems (for example sensors and signals). In addition, the harvested energy can be used to produce electricity for network command centres, power intelligent transport systems, or lighting and signals. Renewable-powered lighting and signage reduces material intensity and emissions.

Intelligent transport systems that are digitised can allow the aggregation and orientation of vehicles into orderly streams of traffic, supporting vehicle drag reduction via platooning. Digital connectivity of vehicle-to-infrastructure, and infrastructure-to-vehicle, will allow for optimisation of traffic flows.

Intelligent transport systems

The Internet of Things (IoT) is a lot more than a buzzword: devices in homes, offices, cities, factories, public transport networks, and more, are now talking to each other. This is now a core part of the fabric of our lives. The IoT includes intelligent transport systems that are able to support transport corridors like the neural networks in our bodies support our densely interconnected brain cells.

Intelligent transport network technologies are existing and available but haven’t reached their full potential to assist with vehicle flow and passenger movement to therefore translate into initiatives that achieve decarbonisation.

The digital data collected from these systems could allow network operators in the future to better understand traffic movements along corridors and determine performance measures for traffic operations and road asset maintenance. They could deliver better travel reliability and real-time traveller information for road users: private and freight.

This ability to optimise existing roads can be developed and extended to produce a variety of environmentally sustainable outcomes:

  • Reducing fuel use and lowering carbon emissions from vehicles with fewer stop-starts by road users, and potentially reducing drag via platooning.
  • Bus lanes (taxis and motorcycles permitted) increasing transit system operating efficiency, directly benefiting bus passengers, and encouraging drivers to shift from car to public transport.
  • Freight management – helping to reduce emissions by improving load factor, finding optimal delivery routes, and improving delivery times.

The road ahead: Safer, cleaner, and more reliable

The market alone is unlikely to achieve the innovations presented in this paper. It will take collaboration within (and across) industries, energy suppliers, public transport network operators, governments, policymakers, businesses and communities. It will take true leadership, foresight and vision and there will be speed bumps along the way.

However, through these innovations our world could ultimately end up with road networks that offer less congestion, are safer, and can be maintained predictively – all contributing factors to decarbonisation.


About the authors

Peter Algie, Associate, Integrated Transport and Mobility, Aurecon. Peter has a strong drive towards a world where waste is seen as a valuable commodity and where clean energy improves the bottom line. Only when this happens can there be mass market adoption and real change towards a more sustainable world.

Ben McGarry, Future Energy Capability Leader, Aurecon. Recognised as one of Engineers Australia’s Most Innovative Engineers in 2019, Ben McGarry is a forward-thinking innovator in the Australian energy market, having worked in energy strategy, infrastructure advisory, project development, project engineering and technology R&D roles in Australia and the US.

Liz Root, Associate, Environment and Planning, Aurecon. Liz brings local and global experience working with organisations and infrastructure delivery teams. She has a real depth of experience in applying sustainability rating frameworks, including the Infrastructure Sustainability Council framework to deliver social, environmental, and cultural outcomes on projects.

Nial O’Brien, Capability Leader for Roads at Aurecon. With more than 20 years of experience, Nial is responsible for roads and highways services at Aurecon. Nial is passionate about the future of roads and what they can offer if we change our mindset about how they are used and managed.

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