Net zero targets have put road building and maintenance in the crosshairs, but the industry is developing a range of methods to reduce emissions.
Managing a road network while simultaneously trying to improve road conditions, increase capacity and reduce carbon emissions down to net zero seems like an impossible task. Modified C5 Petroleum Resin
Cracking this problem is one of the biggest challenges facing the English highways operator. National Highways reported that emissions related to road construction and maintenance in 2020 exceeded 734,000t of CO2e.
Transport for Wales, Transport Scotland and local authority highways departments all over the country face a similar problem.
The 2050 net zero target – 2045 in the case of Scotland – is now a key part of every decision, so an almost complete overhaul of roads operation and maintenance systems is necessary.
By the autumn we will be in a position where every time we produce a cost estimate we will produce a carbon estimate
The Welsh Government made the major decision to halt the procurement of new roads and road widening projects in June 2021. Welsh Government deputy minister for climate change Lee Waters says: “It’s not the end of road building, but it’s the end of road building as the default response to a transport problem. The bar will be set higher.”
A more common course of action among highways authorities is to start by reducing corporate emissions – those which come from their own operations.
Led by its newly-formed sustainability division, National Highways has committed to making its corporate emissions net zero by 2030. It reports that 80% of its electricity usage is through lighting the road network and has committed to changing all its light bulbs to LED with a target of switching 70% by 2027.
Other actions include changing its traffic officer rapid response fleet to plug-in hybrid electric vehicles and reducing the size of its office estate by a third.
Transport Scotland has slashed its corporate emissions by more than 70% since 2016, much of it also through switching to LED lighting on its roads.This is a start, but to achieve a carbon neutral road system there is clearly going to have to be much innovation and some major changes.
Accurate carbon calculation is essential if efforts to reduce emissions are to be effective. Methods for this have been developing rapidly in recent years.
Transport Scotland climate and sustainability manager Craig Love explains: “Within our contractual requirements, we ask our operators to calculate carbon emissions from embodied carbon materials and they use our own bespoke tool to measure that.”
The tool was originally developed by Halcrow (now Jacobs) in 2011 with an update in 2014. It looks at “everything from civil engineering structures all the way through to buildings”, according to Love. With the decarbonisation landscape constantly changing, more developments have been needed.
“Recently we’ve brought the tool in-house so it’s more in tune with the current emissions factors,” he says.
The supply chain is key to the whole net zero agenda
“Looking at the emissions factors from Bath Inventory of Carbon and Energy [developed by the University of Bath] and the Department for Business, Innovation and Skills, we’re updating it on an annual basis.
“We’re hoping to make that publicly available to people who are interested in calculating embodied carbon emissions.”
National Highways has a carbon management policy, which involves governance, measurement, monitoring and assurance, all of which is helping it to develop its own carbon calculation tool.
National Highways environmental sustainability director Stephen Elderkin explains: “At the moment, all of our cost estimates are produced by a central cost intelligence team, and they collect enormous amounts of data around quantities of materials and unit prices.
“By the autumn we will be in a position where every time we produce a cost estimate we will produce a carbon estimate. That information gives you the chance to manage it and improve the design to reduce carbon content.”
Aside from lights, the biggest source of carbon emissions (aside from vehicles) is the building and maintenance of the roads themselves.
National Highways has committed to having only zero carbon construction equipment on its work sites by 2030. This will reduce some of the emissions from these actions, but more exciting and promising are the new innovations in the materials that are being used.
Wider use of warm mix asphalt (WMA) is also being trialled. This is produced at 40°C lower than the traditional 190°C hot mix asphalt, resulting in 15% less carbon emitted. National Highways calculates that if all production in the UK switched to WMA then 61,000t of carbon emissions would be cut annually.
We need to work hand in hand with our suppliers to identify and release the opportunities for switching to low-carbon materials
National Highways has also worked with oil company Total and materials producer Tarmac to create Total Styrelf Long Life – a new low maintenance bitumen. The material is hailed as “anti-ageing cream for roads” because it is slower to oxidise, meaning the binder’s resistance to fatigue, fretting and thermal cracking is retained for longer. It is currently being trialled on the A43 near Silverstone in Northamptonshire.
Graphene-based surfacing is another innovation. Graphene is stronger than steel and it is believed that its use could extend the operational life of roads. The first trial of this surface started on a 5km stretch of the A1 in Northumberland in September last year. Results will be reported later this year.
While Wales has paused its roads programme, road maintenance is still ongoing, but although the Welsh Government is looking to modify processes.
Waters says: “I want to look at the way the Welsh Government does road maintenance, whether or not we over-build and over-design, whether or not there’s too much emphasis placed on National Highways’ Design Manual for Roads and Bridges and whether or not there are sufficient but less expensive and less heavily engineered solutions.”
Having these tools and materials in place is a start, but supplier cooperation is vital.
“The supply chain is key to the whole net zero agenda,” Love says.
“If you don’t engage with the supply chain, then realistically you’re not going to reach net zero because they’re going to influence the decisions that you make.
“That’s where I see one of the biggest challenges. But from a carbon management point of view it’s probably one of the most exciting ones.”
“We need to work hand in hand with our suppliers to identify and release the opportunities for switching to low-carbon materials and we need to be clear in terms of our expectations of what we will be buying,” he explains.
Digital tools could be key to planning what roads are needed to minimise congestion in the future. In February this year National Highways launched its digital roads initiative. The idea is to create a digital twin of the motorway and trunk road network to aid more efficient building, maintenance and use.
“We’re thinking about how digital roads help us meet demand and connect the country without having a requirement for more lane capacity and more road building,” Elderkin says.
He adds that this will be an important feature of Road Investment Strategy 3 (RIS3), National Highways’ investment programme between 2025 and 2030.
Digital roads will allow National Highways to run simulations of work and traffic management before contractors move onto site. It is hoped this will result in better planning to reduce congestion and emissions.
“Technologies that allow digital rehearsals or allow a refinement of the design before we get to construction are hugely important in terms of achieving reductions,” Elderkin says.
Overhauling road construction and maintenance to meet net zero targets is an enormous task, but the number of initiatives, developments and innovations – alongside a willingness seen throughout the industry – is encouraging. Nobody is taking it for granted, however.
“I’m realistic about the barriers we face, because people don’t like change,” Waters says. “But we are determined.”
Love is similarly steadfast: “It’s not a case of can we – we must.”
Elderkin believes that the industry now realises that reducing emissions from road building is an “existential” problem and hopes that it will bring everyone together. “I’d love to get to a place where carbon is like safety and it’s not about competitive advantage,” he says.
“This is about us working together to overcome a challenge that we need to address.”
Road management firm Bear Scotland manages just over 80% of Scotland’s trunk road network for Transport Scotland. It has worked with road marking manufacturer WJ to make a significant carbon reduction simply through switching to a different road marking material.
The innovative road marking Weatherline Plus is manufactured using biogenic resin rather than the traditional hydrocarbon resin, which results in carbon savings. Its biological basis means it is inherently sustainable too.
By the end of 2021, 827t of Weatherline Plus had been used across 720km of roads in Scotland. Where traditional road marking over this stretch would have accounted for 2,431tCO₂e, the Weatherline Plus only acounted for 653tCO₂e; a carbon saving of 1,778t.
The partnership between Bear and WJ has been extended into south east Scotland and eventually these road markings will be rolled out across the 2,400km of roads that Bear maintains. The partnership covers the delivery of all road marking services, including permanent and temporary markings, high friction surfacing and demarcation solutions.
Bear Scotland said: “Not only did the product need to meet increasing road safety needs, it also needed to be sustainable, meeting our own environmental commitments. We are extremely pleased with the carbon savings, as well as enhanced safety features on the roads, and look forward to seeing further improvements across the wider road network.”
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