By Peter Algie, Associate Integrated Transport & Mobility, Liz Root, Associate Environment & Planning, Nial O’Brien, Roads Capability Leader, Ben McGarry, Future Energy Capability Leader, Aurecon

With the imperative to decarbonise, New Zealand’s focus is rightly placed on promoting mode shift to public transport, walking, and cycling.

But our geography and population mean that in some areas at least, roads will remain fundamental to our economic wellbeing and in connecting communities. Roads are currently 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 answer then isn’t simply stripping them of all vehicles, rather it’s about focusing on how we use roads and decarbonise them. This requires a holistic approach to address both embodied emissions (direct emissions created during design, construction and operation) and enabled emissions (from road users).

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

Engineering, design and advisory company Aurecon’s paper unpacks four opportunities to create net zero roads in Aotearoa New Zealand:

This article explores one of these opportunities – reducing embodied emissions.

Reduce embodied emissions in design, construction and maintenance

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 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.

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.

With the emergence of the circular economy approach to infrastructure design and delivery, there is 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-life cycle approach.

Examining these risks at the outset of a roading 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.

To read Aurecon’s full paper, click here.