Paving the way for low-carbon roads and highways

The world’s landscape has transformed over the last two centuries with transportation infrastructure, from trains and tracks to cars and roads, to planes and airports. But the toll on natural resources and the impact of a changing climate is rapidly accelerating in impact.

Roads and highways create a particularly large carbon footprint. According to World Resources Institute, road transportation accounts for 12.7% of global emissions. Up until recently, reducing carbon emissions was a low priority for the design and construction of roads and highways. Design was typically focused on minimizing costs, not carbon. Now that’s changing with a fresh outlook, new government requirements, and breakthrough technologies to help make resilient infrastructure a reality.

The idea of “green roads” might sound like a contradiction, but it is currently underway. For 30 years, Stuart Guthrie, technical director at Sweco, has worked in the transportation infrastructure industry with a specific focus on roads and highways. He’s seeing firsthand the transformative demand for carbon reduction with road construction and maintenance.

“National Highways and Transport Scotland here in the UK are really pushing for carbon reduction,” he says. “They’re setting challenging carbon reduction limits. For instance, National Highways aims to be 40-50% carbon neutral by 2030, and carbon neutral in everything they do by 2040.”

The push for carbon reduction has presented new challenges—and opportunities—for Sweco.

“We now need to build carbon impact into our designs and demonstrate how we're lowering it,” he says. “We start each project with a baseline figure and show the carbon reductions from intermediate to detailed design, as well as how it will affect the project onsite. We are being driven to demonstrate our overall carbon literacy across the project.”

For roads, the choice of materials and assessing their impact are major considerations when it comes to reducing carbon impact. Asphalt production is one of the most carbon-intensive parts of a project, given the heat and energy required. “Asphalt is a hot product,” Guthrie says. “There’s a lot of energy that goes into making asphalt—from drying the aggregates to putting the bitumen in. The transportation from production out to the construction sites is another factor.”

To cut emissions, the Sweco team is exploring alternative materials and processes. This includes warm mix asphalt, allowing the bitumen to be more workable over a wider, usually lower temperature range and reducing energy needs. They’re also testing bio binders, replacing either some or all the bitumen—which is a petroleum-based product—with plant-based products. Another development involves carbon-sequestering additives.

“These are byproducts of other industrial processes which would otherwise go away for incineration,” he says. “By diverting this product and putting it into an asphalt mix, we’re preventing that material from being wasted, and carbon released in its disposal.”

Recycling also plays a crucial role. “Most materials used in highway construction are a hundred percent recyclable,” Guthrie says. “They can be reused as an aggregate or, with adding other things like small amounts of cement, be turned into completely brand-new materials.”

The actual materials are an important component to reduce carbon, but they’re just one part of the equation. Making informed choices across a variety of factors during the early design of roads and highways is imperative. Previously, Sweco’s carbon tracking relied on manual spreadsheets.

“Originally most of our carbon calculators were based in Excel,” Guthrie says. “Every single material of asphalt in the catalog of materials available had a different carbon intensity.”

Projects often had upwards of 20 options, meaning engineers had to go back to that Excel sheet, make alterations, change it, and do the recalculation again. “The result was more of a recording of what we were doing rather than actually using it as a tool that would help us modify the designs,” he says.

That changed when they began to use ORIS Plug-in for Infrastructure LCA with Autodesk Civil 3D to help reduce the environmental impact of road and highway projects. With this technology solution, the team can assess alternatives, select locally appropriate materials, and calculate carbon impact with the integration of carbon data directly into their design workflow.

“Using Civil 3D and ORIS completely automates the workflow for us now, and it’s integrated directly into drawings,” Guthrie says. “What used to take probably half a day now takes seconds.”

The new solution not only saves time but allows for real-time decision-making. “It gives us the opportunity to be proactive rather than reactive,” he says. “Now we can swap materials out very quickly and find out what impact there is on carbon iteratively.”

It also supports Sweco’s goal of making sustainability data more visual and accessible for clients.

“With ORIS and Civil 3D, Sweco’s team can instantly assess and optimize carbon footprints from the very start of each project,” says Renaud de Montaignac, COO & CPO, ORIS. “By turning complex data into visualized insights—like supply chains, transport analysis, and live KPIs—we helped them replace spreadsheets with real-time sustainability data. That transparency helps Sweco’s clients understand and act on carbon reduction strategies with confidence.”

A key project using the new ORIS and Civil 3D workflow is the Aberdeen South Harbor Link Road in Scotland. The local authority wanted to provide better access to the harbor for the next generation of sustainable, offshore wind farm development and the concurrent decommissioning of existing oil fields. Sweco was tasked with upgrading an existing road and adding a new road. Carbon reduction was a priority.

“On Aberdeen South Harbor Link Road, we used ORIS to compare a conventional pavement baseline against a range of lower-carbon alternatives in real time,” Guthrie says. “This allowed us to quantify the impact of changes such as warm mix asphalt, recycled content, and local sourcing, and to show the client clearly how those measures could be combined. The preferred solution delivered a reduction of 34% against the baseline, equivalent to approximately 458 tCO2e.” According to the EPA's calculator, that's roughly the annual energy consumption of 61.5 homes.

By advancing Sweco’s capabilities for carbon reduction, the team can focus on supporting clients by truly listening to their needs, both at a strategic level and in alignment with government goals. According to Guthrie, they now average 30-50% carbon reduction per road construction project using Civil 3D and ORIS together. Plus, they can help clients really understand what can be achieved for meaningful and measurable sustainability outcomes.

“You don’t need to be an engineer to understand it,” Guthrie says. “We can show any of the project stakeholders how easily carbon can be reduced through well-informed changes.”

Combining Sweco’s engineering expertise with Autodesk’s open platform and ORIS, low-carbon infrastructure is accelerating, one road at a time.