Is transport pulling its weight? Reflections on the Carbon budget and growth delivery plan

The Government recently published its whole economy Carbon budget and growth delivery plan (CBGDP). The document sets out the policies, assumptions and risks in delivering the decarbonisation pathway to the end of the 6^th Carbon Budget. This plan follows two previous attempts which were both thrown out in the courts for being insufficient.

The report is important because it follows hot on the heels of the Climate Change Committee’s (CCC) 7^th Carbon Budget published in February 2025 which sets out an indicative pathway through to 2042. My analysis (‘Headwinds: transport decarbonisation in a storm’) of the CCC’s report identified two key questions which the Government needed to resolve in the CBGDP:

1. Were the trajectories proposed by the CCC for the uptake of electric cars, vans and HGVs too optimistic to be delivered?
2. Was there sufficient commitment to deliver a 7% reduction in car mileage through investment in bus and active travel?

Transport remains the largest emitting sector in the economy and a lack of ambition on either of these issues would be problematic for overall carbon budget adherence. Unfortunately, there are issues across both.

Before reviewing what was written in the CBGDP, it is worth reflecting on the challenge to those scrutinising the plan. Once again, the full data set is not available publicly. The sectoral baseline assumptions are absent and whilst the MegaTonnes of Carbon that are anticipated to be saved by different measures are shown, there is precious little information to work out how that was arrived at. True, the documents already stretch to several hundred pages, but there is no ‘companion guide’ on the DfT site which fills any of this in.

The Zero Emissions Vehicle Mandate is, in my view, an excellent piece of legislation in providing clarity and a pathway to phase out the sale of fossil fuel vehicles. What matters to overall in-use emissions though is the number of fossil fuel miles which are being driven. Vehicles are staying in the fleet longer and we are buying fewer new cars than we did pre-pandemic. However, with the data presented, we can only meaningfully compare the % of EVs that will be in the fleet rather than miles driven. Here, the CBGDP figures show the concerns of the Headwinds report to be borne out. Even with the latest support packages around new car electric purchases and charge points, the Government forecasts a much less ambitious adoption than the CCC with around a 9-10% lower adoption rate by 2035. This means there will be more fossil fuel miles being driven for longer in the fleet than the CCC set out.

Source: Table 8 Page 204 of CBGDP and Figure 7.1.4 data sheet from CCC 7^th Carbon Budget

One key plank of policy has been to shift away from car use to other forms of transport, particularly early in the period where the greatest benefit is yielded from reducing fossil fuel miles driven. It is important not to lose sight of the wider decongestion benefits (it is a growth and productivity narrative in the CBGDP), placemaking opportunities and health benefits of more active lifestyles – so there are wider reasons to do this.

The CCC suggested that a 7% reduction in miles driven relative to the baseline assumptions was necessary and that a further push to 10% might be possible if delivery was not as strong elsewhere.

There is precious little evidence of any commitment to mode shift away from the car in the CBGDP. The commitment to 55% of short journeys in towns and cities being by active modes such as walking, cycling and wheeling by 2035 is reiterated. This is welcome. I share the CBGDP’s analysis that this will not deliver massive carbon savings. Even in the most optimistic set of assumptions I could make in Headwinds, it was around 4.2bn miles a year – which would be swallowed up by two years of forecast traffic growth. The CBGDP assesses that walking and wheeling will save 0.07MtC per annum over the 6^th Carbon Budget period (around 0.14% of the anticipated surface transport contribution for the 6^th Carbon Budget period.

More concerningly there is very little other mode shift policy identified in the modelled policy table. Better public transport is mentioned as a sector enabler and, the narrative is used that there will be some moderation of traffic growth. However, the only other modelled reduction in travel demand comes from a growth in car occupancy which I have advocated before – but which has yet to see the necessary policy commitment line up behind to realise it. The lack of action on travel demand is perhaps well summed up in the risk analysis which states that “Unanticipated growth in travel demand, that exceeds the upper range of our projections, is a further risk to achieving anticipated emission reductions.” (emphasis added, p219). Mode shift is a mitigation to this risk but there is no modelled or credible commitment to what this will deliver. I have yet to see a compliant and convincing pathway produced which includes any traffic growth so the policy landscape seems to have moved to mitigating against upper ranges of growth, rather than aiming for what is necessary.

Time and again, the ambition for transport emissions reductions slides backwards. Maybe analysts have got so used to this that it is not noteworthy. The CBGDP does not concern itself with the drift in transport specifically, as it promises adherence to the budgets at a whole economy scale. That is fine, if you believe that no other sector is also looking at its numbers and wondering if it all adds up. It seems quite clear from my reading of the CBGDP that new vehicles and cleaner fuels are the strategy and everything else is pretty much window dressing. I would not argue against the need for a rapid and complete transition away from fossil fuels in the vehicles we use. It just cannot happen fast enough to deliver what we need of it. This is evidenced by the continued rollback of ambition of what can be delivered when on electrification. If all we focus on is the decarbonisation of our vehicles, we will fail to solve the myriad other problems that the transport sector faces. The Transport Decarbonisation Plan is nearly five years old and belonged to a previous Government. It is, at best, yellow round the edges. We are expecting an Integrated National Transport Strategy (INTS) imminently. Will the INTS be so disempowered or disconnected from the decarbonisation agenda as the analysis in the CBGDP suggests? Let’s hope not and keep pushing for a more balanced and effective strategy that delivers wider benefits for society and the economy.