Impact of Local Road Maintenance on Carbon Emissions

This article provides a high-level technical overview of the carbon emission sources associated with local highways maintenance activities across the UK network.

There are a wide range of highways maintenance treatments and innovations used daily on local road networks, each having a different impact on the environment. With over 98% of the UK’s road network made up of local highways, how we maintain these assets has a large impact on our national and local carbon footprint. This article explores how maintenance contributes to carbon emissions, and how innovations in the sector can drive the industry towards a more sustainable, carbon conscious future.

Primary Carbon Emission Sources within the Maintenance Lifecycle

From a lifecycle assessment (LCA) perspective, the key sources of emissions related to highways maintenance include:

·       Material Production – The production of raw components used in maintenance such as: Bitumen, aggregates, binders etc are responsible for a large portion of total emission produced in a maintenance cycle. This being due to the energy intensive production process used in extracting and refining the raw materials.

·       Manufacturing and mixing – The carbon emissions in the production of maintenance related materials, such as asphalt, comes from the heating of fuel and the use of electricity in the energy intensive manufacturing process.

·       Transport – Fuel consumption of the HGV’s and vehicle fleet used to transport materials to both the site and the depot leads to further emissions.

·       On-site operations – The installation of materials on-site using both vehicle fleets and operational machinery consumes more fuel, leading to further emissions.

·       Maintenance – The regular repair of highways assets, whilst essential for safety and performance, leads to further emissions in the assets cycle.

·       Waste and disposal – The disposal of old road materials and assets, such as aggregates and asphalts generates additional emissions through the transportation, processing and disposing of materials.

Carbon Performance: Reactive Versus Preventative Maintenance Interventions

Most carbon emissions for local highways maintenance stems from reactive works such as pothole patching, resurfacing and other service activities. Frequent intensive repairs typically require:

·       Hot materials - Reactive works often require hot-mix asphalt or hot patching materials, which must be manufactured at high temperatures and kept heated during transport.

·       Trips to site – The frequent vehicle trips to site, especially the diesel powered and HGV fleet, add substantial transport emissions.

·       Generate more waste - Emergency repairs generate more waste because damaged material must be cut out, removed, transported, and disposed of.

·       Addressing underlying issues -  Frequent repetition of repairs is required when underlying issues aren’t fully addressed

In contrast, preventative maintenance such as surface dressing, crack sealing and rejuvenator treatments is:

·       Less intrusive – Preventative maintenance is applied to structurally sound roads, this means they don’t require deep excavation, planning or removal of large sections of asphalt. This reduces fuel use, traffic delays and disruption to the public.

·       Quicker to apply – activities like rejuvenation and preservation can typically be completed within hours, or a single shift compared to multiple days for milling and resurfacing. Roads can re-open quicker, minimising delays and disruption.

·       Significantly lower in carbon emissions – Asphaltic material production, especially bitumen, involves energy and carbon-intensive processes. Preventative treatments can extend the asset life, reducing the need for carbon intensive, costly repairs.

Shifting from reactive to proactive approaches is one of the fastest ways for UK local authorities to reduce their carbon footprint.

Emerging Decarbonisation Pathways for Local Highway Maintenance

To bring down emissions emitted from local highways maintenance the UK is embracing:

·       Low-temperature asphalts – these reduce the manufacturing energy use and emissions, by removing the need to initially heat the material to extreme temperatures and maintain this throughout the scheme.

·       Reclaimed Asphalt Pavement (RAP) – contributes to circular economy and reduction of waste materials by re-using the existing materials.

·       Bio-based binders and other bitumen alternatives – cuts the reliance on fossil-based bitumen.

·       Digital asset management – allowing for the right intervention at the right time, increasing maintenance efficacy.

·       Operational and fleet decarbonisation – local authorities have begun to transition towards electric/hybrid vehicles and machinery to reduce emissions.

·       Collaboration and shared learning – no single local authority alone can change the sector. Through bodies such as The Centre of Excellence for Decarbonising Roads the sector can share knowledge, best practice and collectively move towards a low-carbon future.

The Centre of Excellence for Decarbonising Roads is part of a wider UK project named Live Labs 2 - a three-year, £30million, UK-wide programme funded by the Department for Transport that will run until March 2026. We ingest, test and disseminate Low-carbon materials to the sector.

Our recently launched Knowledge Bank aims to support this journey of adopting low-carbon road materials. It contains information and detailed case studies on our project’s trials of a wide range of low-carbon materials. By bringing this knowledge together into one accessible place, the Knowledge Bank aims to accelerate the adoption of low-carbon solutions, reduce duplication of effort across the sector, and build confidence in the materials and methods that can meaningfully reduce emissions. Help us on this mission by sharing your insights and experiences with low-carbon road materials by contributing your case studies here: https://kb.decarbonisingroads.co.uk