In Noticias

A carbon portal is helping Highways England build more sustainable roads.

Earlier this year, the government pledged to ban the sale of new diesel and petrol cars by 2040.

It is a move aimed at driving people to switch to electric vehicles and helping achieve the legally binding target to reduce carbon emissions by 80 per cent from 1990 levels by 2050.

Phasing out the internal combustion engine will go a long way to reducing the 25 per cent of UK emissions associated with road transport. But electric-powered vehicles, whether driven by humans or autonomous, will still require a surface to travel on. Ensuring new roads are as sustainable as possible is also important if the UK is to achieve its climate ambitions.

A low-carbon strategic road network is among Highways England’s major goals. Although its carbon route map, published in 2014, indicates that total embodied emissions from construction and maintenance activity will increase by 2050, the carbon intensity per unit of investment is expected to fall, resulting in significant savings. The main reductions will come from the use of materials, better design and changes to construction processes.

Selecting the right option is crucial to maximising savings, and this is where Mott MacDonald’s carbon portal tool can play a big role.

Simple to use and able to link up with BIM, this tool is now embedded in all Mott’s projects with Highways England, calculating the carbon footprint and providing early assessment of assets for different options at the planning and design stage, while giving a clear breakdown of how much different areas of work contribute.

A decision-making tool

The greatest scope for securing carbon savings is during early phases of a scheme, so Mott uses the portal for the optioneering of projects, ensuring carbon informs the different options and decision-making.

The portal contains asset headline, item, and schedule line carbon data. Each schedule line belongs to a library and represents different sources of carbon. These are construction-related materials, plant and transport, operational energy, and maintenance-related transport, materials and processes. Each line has an associated emission factor.

There are six main greenhouse gases. Some are many times more potent than carbon dioxide in terms of their warming effect relative to mass. Their different emission factors are given a carbon dioxide ‘equivalence’ – kgCO2e. In reality, however, carbon is the critical gas that has to be considered in the course of building, operating and maintaining roads.

Capital and operational carbon are separated. Capital carbon items are treated as one-off emissions. It is up to the owner / operator to decide the period over which operational carbon will be quantified.

The baseline footprint for a project can be built from scratch in about half a day and linked with the project’s BIM model. This means that carbon data can be used inform and influence evolution of the design. Equally, as design changes are made, the carbon impacts are immediately visible. It enables carbon and cost hotspots to be identified and targeted.

Carbon modelling aligns with Mott MacDonald’s commitments under PAS2080, the world’s first carbon management standard for infrastructure, which was launched in 2016 and co-written by Mott. The voluntary standard provides guidance on managing GHG emissions and cutting costs. Crucially, it offers a way of managing carbon by focusing on the behaviour of companies across the supply chain.

Carbon visibility enables asset owners, managers, designers, constructors and product and material suppliers to better understand their impacts on carbon and responsibilities for reducing it.

The portal allows carbon to be calculated as the design progresses, but the final carbon footprint is reported using Highways England’s own carbon accounting tool, which was introduced in 2008 and calculates emissions for operational, construction and maintenance activities undertaken by suppliers on behalf of Highways England. This allows direct comparisons between projects across the network.

Pushing the boundaries

Carbon savings on schemes built using the portal average about 10 per cent, but can often be larger.

Work starts this year on a new junction 10A on the M20 and link road to the A2070 in Kent, the detailed scheme design for which went through the portal. The resulting design refinements will deliver carbon savings of at least 30 per cent compared with similar size schemes built without assessing carbon emissions – 10,165 tCO2e compared with 16,564 tCO2e.

Current Highways England projects assessed using the portal include:

  • Improving the A27 Chichester Bypass in West Sussex
  • Upgrading the A303 between Sparkford and Ilchester in Somerset
  • The A358 from Taunton to Southfield in Somerset
  • A new Avonmouth junction on the M49 near Bristol (pictured, top)

The M49 junction will improve road access and connect Avonmouth and Severnside Enterprise Area to the motorway network.

Materials tend to account for more than 80 per cent of the footprint of a typical project. The portal identified that structural concrete made up 54 per cent of the design. A 4.3 per cent saving was made on structural concrete alone, equating to 117,050 kgCO2e.

These projects are part of the government’s £23bn road investment programme to upgrade England’s network. With such high levels of investment, the sustainable delivery of new roads will become ever more important.

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