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Decarbonising roads has become a key focus in the global push to reach net zero by 2050.
Road construction and maintenance account for a significant amount of carbon emissions for the sector. To effectively decarbonise roads, it is essential to address both operational emissions (from vehicles using the roads) and embodied emissions (from the materials and processes involved in road construction.)
A significant source of embodied carbon comes from materials such as asphalt, concrete, and steel, alongside construction processes like excavation, transportation, and on-site energy use.
Unlike other areas of the built environment where processes can vary between each sector and project, the materials used for road surfaces across the UK vary very little. This is evident in the fact that asphalt is used for over 95% of all UK roads (Asphalt Industry Alliance, 2021).
This means a host of carbon-saving methods can be implemented across the different areas of the UK’s road network to great effect.
Decarbonising road infrastructure starts at the design and planning phase for new roads and extends to the monitoring and maintenance of existing ones. Planners and specifiers from national bodies and local authorities are crucial in setting low-carbon strategies for the construction and maintenance of roads.
Net-Zero Plans
Most local authorities have net-zero targets and strategic plans to meet those targets, but these often lack ambition. While they typically address scope 1 and 2 emissions (covering direct energy use), they often overlook scope 3 emissions, which are much harder to assess, monitor, and address. To drive real change, all action plans should account for scope 1, 2 and 3 emissions. Without this approach, net-zero plans risk missing key opportunities to lower emissions across the entire lifecycle of road infrastructure.
To truly decarbonise roads, both public and private sector projects must align with net-zero goals. While local authorities oversee the majority of roads, some roads remain privately managed. All stakeholders in road construction should commit to net-zero targets and have strategic plans to ensure upcoming road projects align with climate targets.
Reports like the Net Zero Highways report from National Highways offer industry-leading guidance on how to achieve this. It specifies that the use of low-carbon solutions is vital, as is adopting alternatives to other carbon-intensive road construction methods. For example, using electric powdered construction vehicles.
Designing road infrastructure
Designing roads with sustainability in mind means ensuring the reduction of travel times and traffic congestion. Implementing digital roads and eco-routing solutions can ensure more efficient and sustainable road journeys.
It is also important to increase access to electric vehicle (EV) charging stations to support the roll-out of low-carbon vehicles.
Integrating active transport options within the road network, like cycling lanes and walking paths, can also help to reduce reliance on carbon-intensive transport.
The procurement process is a critical stage for reducing carbon emissions before construction begins on an infrastructure project.
Innovative Lower Carbon Products
Procurement strategies should focus on identifying and sourcing materials with lower embodied carbon. If clients specify the use of low-carbon materials, this will lower Scope 3 emissions from their supply chain.
Decarbonisation Beyond Collaboration
Collaborative efforts across the supply chain are essential to achieving meaningful carbon reductions. While project managers and procurement officers play a role in working with material manufacturers to ensure safety and performance standards are met, the reality is that large-scale carbon reduction depends on financial commitment and regulatory support. Without government regulations, incentives, or dedicated funding, councils and national bodies like National Highways may struggle to justify the higher upfront costs of low-carbon solutions - even when the long-term benefits are clear.
The construction phase is a major source of up-front carbon emissions, primarily due to the production and transportation of materials. In fact, 80% of total road construction emissions are in the form of embodied carbon generated by the production process of materials used to build roads. (McKinsey, 2022). Switching to low-carbon construction material alternatives is, therefore, critical to achieving decarbonisation goals.
Low-Carbon Solutions and Techniques
One of the most significant opportunities to reduce emissions in the construction phase is the use of low-carbon alternatives to traditional materials. For instance, using warm-mix asphalt instead of hot-mix asphalt can reduce the embodied carbon of a project by around 15% (CIHT, 2023).
Additionally, incorporating biogenic binders - even in small quantities - can further lower the carbon footprint of asphalt by up to 23% (Atkins Réalis, 2023).
The use of recycled materials, such as incorporating reclaimed asphalt pavement (RAP) into new road surfaces, can also help to reduce the carbon footprint of a project. RAP also plays a crucial role in conserving natural resources and reducing the need for quarrying and virgin material extraction, making it a key material for more sustainable road construction beyond just carbon savings.
ACLA®, LCM’s innovative carbon-negative aggregate, sequesters a significant amount of carbon dioxide, which is permanently stored in the road. The volume of aggregate used is able to balance out the embodied emissions, resulting in net zero asphalt.
Transport and Logistics
Transport of materials and machinery must also be factored into efforts to minimise carbon emissions. For National Highways, the transport of materials to their sites is the second largest source of their construction and maintenance emissions at 24%. Specifying lighter materials or materials that are needed in lower volumes can help cut transportation emissions. The use of low-emissions vehicles, lower-carbon fuels and machinery powered by renewable energy sources will all help lower the carbon footprint at this stage.
Even after the road is built, the maintenance phase offers opportunities to reduce carbon emissions over the infrastructure's lifecycle. Most carbon reduction methods during this stage are similar to those needed in the construction phase, such as using low-carbon materials and low-emissions transportation. Additionally, smart monitoring technologies can further cut emissions by reducing the need for physical site visits and enabling more efficient, data-driven maintenance planning.
Durable Materials
Aside from using low-carbon materials when resurfacing and maintaining, it is important to select materials that enhance durability. By increasing the lifespan of asphalt surfaces, the need for premature resurfacing will be minimised, leading to reductions in both material use and carbon emissions. Durability is critical in any low-carbon road - if a material shortens the lifespan of a road, the increased frequency of resurfacing could negate any carbon savings.
Future Thinking
Since the majority of the UK’s roads have already been built, maintenance is a key area to maximise decarbonisation efforts. During the maintenance stage, it is vital to consider future use scenarios and end-of-life. Adopting circular economy principles - such as reusing and repurposing materials - can help reduce emissions and resource consumption when repairing or renovating roads.
One approach is incorporating reclaimed asphalt pavement (RAP) into new asphalt mixes. While RAP currently provides modest carbon savings, innovations in material processing, binder rejuvenation and project organisation could enhance its impact. For example, in-site recycling - where existing asphalt is removed, mixed with virgin materials, and relaid on-site - offers more carbon and cost savings by minimising transport emissions.As industry techniques continue to evolve, new technologies and innovations will play an increasingly important role in lowering the carbon footprint of road maintenance while maintaining high performance.
Aside from processes relating to the construction of road surfacing itself, other areas relating to road infrastructure can contribute to decarbonisation.
Increasing energy efficiency
The replacement of all road lighting with LED technology can significantly decrease emissions relating to energy usage across the road network. In road management, the majority of electricity use is driven by road lighting. LED replacements can reduce energy requirements by around 30% (McKinsey, 2022).
Renewable and circular initiatives
Using the real estate of the road network to deploy renewable energy systems like solar panels is a reliable option for the self-production of clean energy for road lighting and EV charging stations. Circular activities can be leveraged across other aspects of the road network to increase decarbonisation and improve sustainability. These include recovering and recycling road surfaces for reuse, implementing systems for water runoff recovery, ensuring effective waste management, and enabling the conservation of biodiversity across the road network’s green areas.
Decarbonising road infrastructure can be challenging and requires action at every stage of the process, from design and planning through to construction and maintenance. By embracing low-carbon options and thinking strategically, professionals at local and national levels can significantly reduce the carbon footprint of the road network. However, meaningful progress will only be achieved when policy and funding align with ambition. While many local authorities and industry bodies have set net-zero targets, the lack of binding regulations and sufficient funding means that low-carbon road construction remains the exception rather than the norm.
