Carbon and the strategic roads programme

Guest blog by Phil Goodwin (Emeritus Professor of Transport Policy, UCL and UWE; Senior Fellow, Foundation for Integrated Transport)

I have been working for many years on problems in road appraisal, including on traffic forecasts, induced traffic, the treatment of alternatives, the value of time (and comfort and convenience) the effects of wider objectives, the consideration of longer-term issues of demographics and land use changes, and the techniques of adding these into a ‘benefit cost ratio’. In later blogs I’ll discuss some of those wider questions.

Last year I was approached to write a witness statement for TAN’s legal case against RIS2 (the Government’s £27 billion roads programme). Most of the issues listed above are not included in the TAN challenge, which focuses on whether the carbon impacts were properly considered.

Therefore, clearly my statement does not attempt to summarise the whole political and professional debate about road building and its relationship with carbon dioxide emissions from transport; that is not its function. Rather it is a technical assessment of the way in which the Department for Transport (DfT) has treated carbon as being too small to make any substantial difference. In scheme after scheme, the carbon effects are described as ‘negligible’, ‘not significant’ and would ‘not have a material impact’.

My evidence suggested that this is not a true statement of the effects. In the statement I report:

  1. there are elements of the carbon impact which had not been taken into account in the appraisals, for example impacts in the longer term of extra carbon from the manufacture of additional vehicles, and changes in land use which are encouraged by road building. Thus the appraisals only estimated some of the carbon effects;
  2. Even so, Highways England’s own appraisals added up to a figure, over the whole lifetime of all of the schemes in the programme, some 100 times higher than the DfT’s summary statements to Parliament and in their own witness statements. This arose because the DfT had only included a minority of schemes, for a short period not the whole scheme life, and then only for user tailpipe emissions, not including construction and other impacts;
  3. In addition, the DfT had chosen a special metric to assess the size of the impact: carbon effect of the scheme as a percentage of all carbon emissions in the whole economy. This can only produce an apparently very small number, but is not consistent with all other appraisal practice where small changes in one aspect are seen to be important in their specific context or when added together with other impacts. Carbon emissions are the only effect I am aware of that are assessed in this way, which has the inevitable effect of making carbon effects seem numerically small even when they are highly important;
  4. The scheme appraisals did not take into account great uncertainties in the traffic forecasts on which they are based, for example that projections of the effect of electrification of vehicles would increase traffic congestion and offset carbon reductions.

Further information on the RIS2 challenge can be found here, while the DfT’s underestimation of the carbon generated by new road schemes has been covered in The Guardian and on Sky News. A longer article on the issues above can be found in Local Transport Today (820).


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