“Is this new road OK? It’s only a bit more carbon…” A guide to carbon budgets and new infrastructure development

By Professor Greg Marsden

The choices are simple, it’s the answers that some organisations don’t like.

This article is a very short and simple guide to explain the impacts of carbon budgets on new infrastructure development. I apply it to roads, but you can also use it to think about new airports, terminals or, indeed, major public transport investments. Currently the carbon accounting of Highways England’s RIS2 budget is taking the bulk of the headlines (and rightly so). However, there are many other road schemes on local authority books and sat in strategy documents that pre-date the move to a 100% carbon reduction target. These appear small when compared with the totality of carbon emissions in the UK. Does that mean we can ignore the emissions these plans will create?

Here, I set out four simple tests to tell whether a scheme is justifiable:

Test 1: Have you set a ‘Paris compliant’ carbon budget?

This does not mean just setting an end date when you would like everything to be zero emissions. Have you set a trajectory for carbon reduction across the economy in your area? Have you set out how transport will contribute to that on the way to getting to zero? If not, no road scheme can possibly be justified. As a starting point, have a look at this resource on Getting Carbon Ambition Right.

Test 2: Is there a carbon budget compliant transport strategy in place?

Ooh… If the first one was difficult then this one is, thus far, proving impossible. Leeds City Council, an authority we do a lot of work with, has set out a bold transport strategy for the period to 2030 when it aims to be zero emissions. It will require increasing bus use by 130%, rail by 100%, cycling by 400%, walking by 33% and reducing car use by 30%. This is set against a backdrop of declining public transport. Amazingly, it can be done. However, their strategy would still only reduce emissions by 43% if fully implemented. This clearly shows the scale of the problem. Once you have a budget the constraint posed by it becomes real. I look forward to seeing fully Paris compliant strategies – but I have yet to see any.

Test 3: Is this scheme part of that carbon budget compliant transport strategy?

Sticking with Leeds’ draft strategy just for a bit longer: that 30% reduction in traffic matters. What is the case for the new road scheme built around? Either the transport strategy works and traffic levels fall, in which case the road scheme is probably not needed, or traffic continues to increase indicating that Test 2 has been failed anyway. For a road scheme to help with mode shift it needs to improve the conditions for non-car users more than it does for car users and, given the scale of change evidently required, non-car users must be given considerable priority. If the scheme can evidently demonstrate this and it is part of a carbon budget compliant strategy then we might be able to progress. However, most of the schemes on the books today are legacy projects from the last decades when congestion reduction was king, not carbon.

Test 4: Are the other parts of the strategy being delivered?

This might be me being cynical, but research (and simple observation) has shown that strategies get picked apart and the easiest bits done first. These have tended to be the bits which have the most funding or which are less restrictive on travel. But then the difficult bits do not get done and so the promise of restrictions on cars once the alternatives are better remains tantalisingly out of reach…

Flowchart - is this new road consistent with your climate commitments?

Of course, if you can answer yes to all of these questions then you can proceed to take the scheme through the standard assessment processes. However, I don’t honestly think that we have any places in the UK at the moment who could say yes to all of the above.

Such a conclusion could cause an outcry, of course. ‘How damaging would it be to our economy not to build infrastructure?’ etc etc. There are two key points to make:

  • It is not a ban on road investment forever, but it is a requirement to say no until vehicle technology and infrastructure emissions are at or near zero.
  • There are lots of low carbon infrastructure investments which could be deployed with very high benefit cost ratios and great carbon, public health and productivity outcomes in active travel and public transport connectivity.

If you still come to the conclusion at the end of this article that a small amount of additional carbon is OK, then flip this argument to congestion. If we had a national goal to cut congestion, would it seem sensible to build schemes which added congestion? No. Budgets are constraints and that means choices have to be made. Hopefully, as this flow chart suggests, these are not actually difficult choices, it is just that the answers do not fit with some people’s preferences.