TAPAS.network | 23 May 2023 | Commentary | Greg Marsden

Reverse gear: The reality and implications of national transport emission reduction policies

John Siraut

Following his successful Freedom of Information application to obtain details of the Department for Transport’s assumptions about achieving Net Zero for UK Transport, Professor Greg Marsden has led a detailed analysis of that data, and other recent government policy documents. The results have just been published, revealing what the report sees as significant back-tracking on the original commitments. We invited Professor Marsden to summarise those conclusions, and add some further observations about what it all means for local transport

IN 2021 THE UNITED NATIONS Secretary-General issued a ‘Code Red’ warning for humanity, with the risks of exceeding the dangerous and potentially irreversible 1.5 degrees of global warming, that Governments had pledged to seek to avoid, becoming perilously close.

That year also saw the publication of the Department for Transport’s Decarbonisation Plan (TDP) and the UK’s Net Zero Strategy, which the Government were keen to have tabled in the run up to the UK hosting COP26 in Glasgow that autumn.

Transport is the largest emitting sector of greenhouse gas emissions in the UK, and for the first time, projected pathways to zero emissions had been produced. The publication of the Transport Decarbonisation Plan and other key strategies such as Bus Back Better, the Williams-Shapps Rail Review, and the Gear Change plan to promote more Active Travel, seemed to spell out an optimistic picture for a more sustainable, equitable and balanced decarbonisation of the transport sector.

In March this year, just 21 months after the publication of the Transport Decarbonisation Plan, a revision to the whole of government Net Zero Strategy – the Carbon Budget Delivery Plan (CBDP) – was released, setting out a new carbon reduction pathway for transport. The Analysis now published by Leeds University in collaboration with the DebarboN8 project and the Centre for Research into Energy Demand Solutions (CREDS), reveals that 72 percent of the potential ambition set out in the original TDP has been lost in the new CBDP. The emphasis is almost wholly now on achieving the transition to electric vehicles and decarbonising ports and airports, with previous elements of carbon reduction by demand management largely abandoned.

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72% of the potential ambition set out in the original TDP has been lost in the new CBDP. The emphasis is almost wholly now on achieving the transition to electric vehicles, with previous elements of carbon reduction by demand management largely abandoned.

There must be severe doubts that this strategy will deliver sufficient carbon reduction, and thus one of the key aims of this review, has been to understand the specific roles of energy demand and behaviour change in accelerating the transition to a zero-carbon energy system, including the technical, social and governance challenges, including the role of demand reduction, flexible demand and use of decarbonised energy.

The Government’s change of direction seems to be a result of a post-Covid re-alignment. Assumptions are based around the Core National Road Traffic Projections (which shuts off a lot of the traffic reduction ambition) coupled with the likely outcome of the Zero Emission Vehicle Mandate (which, whilst ambitious, downgrades some of the more fanciful technology adoption targets in the TDP). However, the package does not look balanced, as we are planning for lowering motoring costs through electrification. This will likely further undermine mode shift aspirations and drive up congestion as we continue with a policy of unrestrained road use. It will also widen the social inequity of per mile travel costs for the EV haves and have nots.


Transport has been the laggard sector in carbon reduction for 30 years. It is now the largest emitting sector. The direction set out in the CBDP to go even slower is a continuation of the “exceptionalist” mindset on transport emission reduction. It may of course be argued that other parts of the economy can go faster and take up the slack, if transport gets a soft ride. It is the job of the Climate Change Committee (CCC) to assess those arguments from a carbon perspective across the whole economy. It would, though, be surprising if the paring back of the earlier stated ambition was deemed acceptable, given the short time that has passed since the 2021 pledges and the seeming lack of commitment to demand management relative to the CCC’s view of what was then possible.

The Climate Change Committee thought that far more carbon reduction was both necessary and possible from behaviour change at the end of 2020. It is deeply worrying that transport appears to have stepped back on much of its potential ambition for decarbonisation. Maybe that ambition was never really on the table. I am struggling to see a set of futures where we make the per mile costs of motoring cheaper, plan for traffic growth and also deliver significant behavioural change.

Whatever assessment the CCC reaches, however, from a transport system perspective, the current strategy makes little sense. Pursuing a technology-led strategy, with no adjustment to prices, seems likely to increase levels of traffic and congestion, and widen transport inequalities between different kinds of transport user – especially those not well-placed to ‘go electric’, missing the opportunity to deliver a fairer transition which drives up well – being and productivity.

This report does show that pathways which track the Government’s aims on electrification could still be consistent with the CCC’s Balanced Pathway if a 20% reduction in road traffic levels were also to be achieved by 2030 relative to current plans. The policy goal in Scotland is for such an absolute reduction in car kilometres of 20% by 2030, although progress against the goal is yet to be substantially realised. Traffic reduction cannot be wished for; it needs to be made to come about. The ambitions of the CCC for the 6th Carbon Budget for surface transport are, therefore, off the table and the policy portfolio, as currently constructed, means that government is planning for traffic growth.

In 2021, CREDS published a series of scenarios, referred to as Positive Low Energy Futures (PLEF). The PLEF transport report set out alternative pathways which could save energy and carbon, but still allow society to flourish (Brand et al., 2021). But such pathways with reductions in car mileage would require a step change in funding and delivery of alternatives to car travel which are not currently being planned for. And every year that passes with a business as usual transport delivery mindset, reduces the potential to shift to such pathways.

These issues of change and transition have resonance at local as well as a national level. Indeed, much is being made of the next round of Local Transport Plans (LTPs) in England as offering additional carbon mitigation through a process of the local transport authorities declaring “quantifiable carbon reductions’’. However, the guidance on such measures is still to be issued, and there is no indication that there will be anything more than business as usual funding made available. If that is correct, then most of the savings from the LTPs may have already been factored into the baseline conditions, and so will not accelerate the mitigation effort.

Many Local Authorities, Combined Authorities and Sub-national Transport Bodies have set transport emission reduction targets for zero emissions which are now well in advance of the pathway the national government deems necessary. So where next? Two options stand out:

  • The national position is accepted, local targets are re-interpreted as ‘aspirations’ and the real carbon ambition is pushed back by a number of years.

  • Local authorities, businesses and citizens insist on a different approach from national government. Significant transport demand reduction is put back on the agenda which enables the delivery of a fairer and faster transition.


The second approach raises difficult issues. How would such ambition well beyond the national scale be received? More importantly, how could it be funded? Does it make sense to have National Highways planning for Core growth in the National Road Traffic Projections (NRTP) whilst the local authorities whose areas it’s network run through plan for less? It might be instructive to look at the different policy positions in Wales and Scotland where traffic reduction targets (per capita and absolute) are in play. However, will macro decisions on tax, funding and technology change enable meaningful divergence in outcomes?

In order to write this analysis, it was necessary to force the Department for Transport (DfT) to open up the data surrounding the original Transport Decarbonisation Plan through an FoI request. What emerged looked an incomplete and unlikely scenario – that in any case now seems abandoned with publication of the new Net Zero Strategy, and the revised transport dimension to it. The issues of policy and its implementation apart, it is regrettable that clarity and openness have been absent in much of this policy-making and pathway mapping. Only through transparent accounting and careful scrutiny can the shifts in policy position be understood and communicated.

Whilst it is frustrating to be wrangling over what transport decarbonisation policy really means, it is crucial that we have transparency. The simple reading of my analysis of the FOI data as soon as I saw it, was that the range of possible traffic levels and technology uptake that underpinned the Transport Decarbonisation Plan was so broad that it would be difficult to identify outcomes that do not fit within the fuzzy green bands set out. The Net Zero Strategy subsequently narrowed the range of outcomes and it became clearer that only the most ambitious end of performance was consistent with the 6th Carbon Budget estimates of what transport should achieve.

It might be tempting now, again, for the DfT to push this report to one side as it does not recognise the numbers in it. But if the assumptions held by DfT do actually differ from those presented in the report, and the data sheets published alongside it, then it is surely essential they should be published. I’d rather we had clarity than speculation.

The recent Transport Data Strategy (DfT, 2023) says many of the right things about open data, but the principles are not yet routinely put into practice everywhere, and particularly not on decarbonisation projections, as indicated. National and local governments need to be held to account for the actions they propose and the ones they avoid. The atmospheric concentrations of greenhouse gases are only affected by the delivery of policy, not the storylines.

The next key step in this process will be the CCC’s progress report to Parliament in the next couple of months. Will they accept transport backtracking on its ambition and, if not, how will DfT respond?

Both I, and I suspect most local transport authorities and their transport officers, will be awaiting those developments with considerable interest.

Reverse gear: The reality and implications of national transport emission reduction policies (pdf)

Greg Marsden is Professor of Transport Governance at the Institute for Transport Studies at the University of Leeds. He has researched issues surrounding the design and implementation of new policies for over 20 years covering a range of issues. He is an expert in climate and energy policy in the transport sector. He is the Principal Investigator on the DecarboN8 network where he is responsible for integrating a new place-based approach to decarbonising transport. 

This article was first published in LTT magazine, LTT869, 23 May 2023.

The Government’s new projections for sectoral carbon budgets

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