Executive Summary

Policy Context

This briefing is set within the context of the climate emergency and the significant gaps which exist between stated ambitions and plans, and the necessary carbon trajectories to ‘keep 1.5 °C alive’.

Very significant demands for new infrastructure are put forward by bodies at the National, Sub National and Local level, and the National Infrastructure Commission is beginning work for the second National Infrastructure Needs Assessment.

However, partly as a result of central government siloes, the carbon implications of infrastructure have not been adequately considered in the strategic cases advanced to date. This has to change and there is an appetite for this to happen.

Key findings

  • All new transport infrastructure generates carbon emissions in its construction, maintenance and operation. The technical reports which sit behind this policy briefing quantify those emissions for typical road and rail schemes.
  • Even with generous assumptions about the potential for technical innovations to decarbonise the construction process over time, there remains a core of emissions which is hard to decarbonise. Investment in innovation and pilot zones is critical to accelerate the gains which are possible.
  • In the case of roads, the emissions from construction are unlikely to be paid back by operational improvements. In some cases, increased use of the road will also worsen the emissions burden.
  • In the case of public transport infrastructure, one of the aims is to enable lower car use and therefore many schemes will be more than able to ‘pay off’ the emissions they generate in construction. However, here too, the ‘pay back’ period needs to be understood.
  • The emissions from maintenance of the existing network are at least as significant as new build emissions and these must also be tackled.
  • Some organisations are promoting the use of offsetting techniques to mitigate carbon from construction. Investing in solar and tree planting may be necessary, but such investments are not intrinsically linked or necessarily part of the case for any new infrastructure. They may be needed anyway. No offsets should be counted in the case for infrastructure with the focus being on reducing emissions at source.


  1. The carbon impact of infrastructure counts and needs to be counted as part of carbon budgets of authorities promoting or maintaining infrastructure.
  2. It is necessary to begin asking ‘what transport infrastructure will we need in a zero carbon future?’ and to stop asking whether investments can still be justified despite their carbon costs.
  3. Getting to zero carbon is going to require a radically different set of policies. Even with full electrification at pace, reductions in car miles will be necessary, as will significant increases in public transport and active travel. This means we also need a different set of infrastructure investments to those currently planned.
  4. Nowhere is yet on track to bring transport emissions down in line with the carbon budgets set out in legislation and national policy. Funded and credible strategies and commitments are needed before we can determine whether specific projects or programmes are appropriate in carbon terms.
  5. It is critical that we stop borrowing on the carbon overdraft by building new infrastructure before we have established whether we can afford to pay it back.

Read or download the underlying technical reports:

Measuring Railway Infrastructure Carbon

Measuring Road Infrastructure Carbon