Select Committee on Environmental Audit Minutes of Evidence

Supplementary memorandum submitted by the Department for Transport

  This memorandum responds further to the Committee Session of 14 June where the Secretary of State for Transport gave evidence.


A.  What is the impact on carbon emissions of the road schemes that are being built, in particular for the 35 major road schemes built since 2001 and the M6 Toll road? How this was calculated?

  1.  Our modelling suggests the impact to be significantly less than 0.15 million tonnes of carbon (MtC).

  2.  The impact on carbon emissions is estimated at different levels of detail. Modelling provides a strategic assessment of the impact of the roads programme, whilst appraisal provides more localised information on individual schemes.

  3.  The National Transport Model is a multi-modal surface transport model. It covers walking, cycling, bus, rail, light rail, cars, vans and lorries. It can provide estimates of the effect on each mode and on emissions of CO2, NOx and PM10.  It has considerable detail on the household composition, area type, road type and time of day. It can show the effect of changes to policies and other inputs, including on capacity and prices. Details of the model can be found at:—econappr/documents/divisionhomepage/030708.hcsp

  4.  Results from the model have suggested that Highways Agency road improvements, as assumed in our modelling for the Future of Transport White Paper, would add around 0.16 MtC in 2010 for Great Britain. The equivalent figure for England is around 0.15 MtC.

  5.  Modelling of 45 schemes in the Highways Agency Targeted Programme of Investment (TPI) in 2000—which includes 31 of the 35 schemes completed since 2000—suggests these schemes would add around 0.03 MtC in 2010.

  6.  The relatively small impact reflects two conflicting results of road investment. Enhanced capacity reduces congestion and can improve the fuel efficiency and reduce emissions of vehicles. However there will be some increase in traffic levels—around ½% in 2010—which off-sets this gain.

  7.  In addition, these figures need to be seen in context. In particular, the modelling performed for the Future of Transport White Paper in 2004 suggested that (in the absence of the SR04 road programme and other transport policies) carbon emissions from transport would increase by nearly 3 million tonnes between 2000 and 2010.  The main drivers of this increase were a growth in freight traffic and assumed increases in population and incomes leading to an increase in distance travelled by car.

  8.  Recent modelling also suggests that other transport policies (eg sustainable distribution, public transport investment and smarter travel choice measures) would reduce annual emissions from surface transport by 0.8 MtC between 2000 and 2010.  More recently we have announced the Renewable Transport Fuels Obligation that is expected to reduce emissions in the UK by a further 1.6 MtC by 2010 (though only a net global reduction of 1MtC, once production abroad and transport of the fuel is taken into account). Consequently the modelled impact of road schemes on carbon emissions is rather small in comparison to "background growth" and the total savings that we expect to achieve through other transport policies.

  9.  An alternative method of calculating the impact of the 35 schemes would be to sum the carbon impacts of individual schemes according to their estimated impacts as detailed in each appraisal. Appraisal allows a more detailed assessment of the economic, social and area specific environmental impacts of a particular scheme. However, this may not give an accurate picture of the total emissions from all schemes, as the interaction between individual schemes may not be taken into account in appraisals. Strategic modelling as described above, looks at cumulative impacts across the network and therefore gives a more accurate aggregate picture.

  10.  There have been several significant developments in the Department's approach to appraisal since the mid 1990's.

  11.  In 1998 the New Approach to Appraisal (NATA) was introduced which provided a consistent and compulsory framework to the assessment of environmental and social impacts. In particular it made the assessment of carbon impacts compulsory.

  12.  Prior to this, the assessment of carbon was not always completed, nor was it always consistent. For example the M6 Toll Road went to public enquiry in 1994/5.  As such the appraisal information was completed prior to the introduction of NATA. A technical paper written in 1994 suggested the new road would reduce carbon emissions by 0.01 to 0.02 MtC. Our methodology for calculating carbon dioxide has much improved for schemes coming forward now.

  13.  Twenty seven of the schemes completed since 2000 undertook statutory planning procedures prior to the introduction NATA. A New Deal for Trunk Roads in England: Understanding the New Approach to Appraisal estimated carbon impacts for twenty of these schemes. These are summarised in the table below.

  Additional Carbon Dioxide Emissions (tonnes) Number of Schemes 0-2000 18 2000-5000 1 5000+ 1

14.  Since 1998, appraisal methodology has continued to improve, reflecting scientific and other advances. Schemes now have more precise estimates of the carbon impact. A total of eight schemes completed since 2000 have these more detailed estimates, and are outlined at Annex A.

  15.  Two of these schemes—the M4 Junction 18 and M5 at Hallen Hill—have been assessed under the latest value for money process; which provides a single assessment of the economic, social and environmental implications of the schemes.

  16.  The Department continues to refine and improve the appraisal process and the way it is used to advise decisions. Further guidance on the assessment of carbon impacts is currently being prepared.


  17.  The Committee Clerk followed up the 14 June evidence session with some further questions, which are set out below with the Government's response.

B.  In the context of saying that the RTFO will achieve the equivalent of taking a million cars off the road, what is the basis on which DfT calculates the average carbon emissions per car per year (ie what are the factors you use—presumably, average miles per year, average fuel consumption per mile, and average carbon emitted per litre of fuel—and the values you give for each).

  18.  A thorough economic analysis has been undertaken to estimate the impact in terms of carbon savings, costs and benefits of the RTFO. This estimated that the RTFO would result in net carbon savings in the region of 1MtC (million tonnes of carbon) in 2010.

  19.  As an illustration of what this means in terms of carbon emissions from cars, we carried out a calculation as follows:

    —  Take average fuel efficiency of a car on the road today (around 180g CO2/km)

    —  Multiply by average annual mileage (eg 15,500 km) to give average CO2 emissions from a car over a typical year. 15,500 x 180 = 2.79 tonnes CO2

    —  Multiply by 12/44 to convert CO2 to carbon = 760,909 g C.

  20.  Therefore, since the average car emits something like 0.76 tonnes of carbon a year, saving a million tonnes of carbon is the equivalent of taking at least a million cars off the road. Alternatively on this basis a million tonnes of carbon is equivalent to taking about 1.3 million cars of the road, thus our estimate of one million cars is cautious.

C.  What is DfT's methodology for calculating the likely net effect on carbon emissions? How is this impact taken into account, within appraisals of major transport proposals (eg those costing more than £5 million)

  21.  DfT's approach to appraising the costs and benefits of transport schemes is consistently applied across all modes since the introduction of a New Approach to Transport Appraisal in 1998. The guidance for this process is available from

  22.  Proposed road schemes are subject to a detailed assessment which looks at their impacts on the environment, the economy, road safety, accessibility and integration. These five objectives have several sub-objectives against which the schemes are assessed. The impact of a transport scheme on greenhouse gas emissions is one of 10 environmental sub-objectives that are considered.

  23.  The basic appraisal method is the same across modes and is set out in Webtag (see the link above). Estimates of carbon dioxide emissions are made for a base year (current year), the opening year of the scheme without the scheme in place, and the opening year of the scheme with the scheme in operation.

  24.  A key step of appraisal is to use what we know about the relationship between different traffic speeds and traffic flows for different types of roads. We use this to estimate what the average traffic speed will be if a certain scheme is implemented. This change in average speed gives us a change in generalised cost (ie time and money cost), which is used to estimate the impact on traffic.

  25.  An investment that speeds up traffic reduces generalised cost and will tend to increase the number of people using the road. Our understanding of how to estimate induced demand has been improving over time. More details on induced traffic is set out in a report by the Standing Advisory Committee for Trunk Road Assessment on Transport and the Economy (1999).[2]

  26.  Carbon emissions are calculated using levels of traffic and emission factors from the National Atmospheric Emissions Inventory, which estimates the fuel efficiency of vehicles at different average speeds.

  27.  A road investment will generally increase carbon emissions as induced demand increases total traffic—but this may be mitigated by a reduction in congestion which means that traffic may travel at a more fuel efficient speed.

  28.  The next step of the appraisal is to work out a monetary value for the carbon dioxide impacts. This monetised value then feeds into the value for money assessment, where it is weighed against the other quantified and qualitatively described appraisal objectives and sub-objectives.

D.  How many road projects have been turned down because of their carbon emissions?

  29.  Ministers make decisions on individual schemes taking account of a variety of factors, including:

    —  Value for money (including economic, social and environmental impacts).

    —  Practicality/deliverability.

    —  Public acceptability.

    —  Distributional and equity impacts.

    —  Affordability and financial sustainability.

    —  Contribution to central government, local and regional objectives.

    —  The amelioration of identified problems.

  30.   The Value for Money process provides a single measure of all of the impacts of a scheme—economic, social and environmental—based on an appraisal of the scheme. This includes the impact of carbon emissions.

  31.  Decisions on approval of schemes are based upon the aggregated impacts not on the contribution of individual elements. Taking account of non-monetised environmental impacts (eg including carbon emissions, landscape impacts and biodiversity) in scheme appraisals can have a significant impact on the overall value for money of schemes, upon which advice to Ministers is based.

  32.  As the value for money appraisal takes account of the environmental impacts and adds them into the decision making process, they rarely provide the sole basis upon which schemes are considered. Rather the environmental impacts as quantified through the value for money process, add further detail to decision making, which is considered alongside the other factors set out above.

  33.  All major road schemes are subject to a value for money assessment and are put into high/medium/low/poor value for money categories. Value for money appraisal includes enviornmental and non-monetised impacts. About 1 in 6 road schemes have a lower value for money category as a result of environmental impacts.

  34.  We first undertook value for money appraisal for major schemes in 2004.  Analysis of local transport schemes, costing over £5 million, which were submitted by local authorities to the Department for funding through the Local Transport Programme, showed a clear link between value for money and the decisions.

  35.  Significant adverse environmental impacts that were key in the decision to reject the funding bids for:

    —  A36 Wylye Valley Relief Road,

    —  B1108 Norfolk hospital road, and subject to review

    —  A36 Codsford to Heytesbury improvement.

  36.  These are not the only schemes in this category. They are the only schemes from the 2004 local transport plans.

E.  A breakdown of the figures given in CCP2006 for projected carbon savings from the current VA package, by the constituent parts of that package, in particular giving savings figures for the VA alone, and for the increase of "eco-driving" alone

  37.  There are a variety of policy measures in place that provide incentives for manufacturers to produce, and consumers to purchase, more fuel efficient cars. These include the EU Voluntary Agreements on new car fuel efficiency, and the fact that Vehicle Excise Duty and company car tax are both linked to a vehicle's CO2 emissions.

  38.  Unfortunately, it is difficult to isolate the impact of these individual policies on vehicle fuel efficiency since all are contributing to the same outcome. Apportioning the resultant carbon savings to individual measures is therefore difficult to achieve with certainty. As a consequence, the work we carried out for CCP2006 evaluated these measures as a "package". Our estimate was that this package of measures would generate carbon savings of 2.3MtC in 2010.  However, as an illustration of the magnitude of likely carbon savings arising from the company car tax, HMRC have provided an indicative range of 0.35 to 0.65MtC saved in 2010.

  39.  Carbon savings arising from wider transport measures set out in the 2000 Ten Year Plan and the Future of Transport White Paper were calculated using DfT's National Transport Model (NTM). The measures include substantial improvements in local public transport; various soft measures such as school travel plans; and development of the sustainable distribution programme involving both Government and the haulage industry. This latter policy programme provides drivers and fleet operators with best practice advice on fuel-saving measures and promotes safer and more fuel-efficient driving.

  40.  These wider transport measures are estimated to save 0.8MtC in 2010.  The impact of these measures in Scotland was evaluated separately and estimated to save 0.1MtC. Analysis of the impact of individual measures on carbon emissions was not carried out, due to difficulties in obtaining reliable data and the synergies between the measures making it difficult to strip out their individual effects.

F.  The basis on which DfT measures the increase in "eco-driving", and calculates carbon savings resulting from it

  41.  The government has a sustainable distribution programme which is targeted at the road haulage sector and provides drivers with best practice advice on fuel-saving measures and promotes safer and more fuel-efficient driving.

  42.  Analysis based on evidence from case studies suggests that sustainable distribution policy can deliver carbon savings. For example, an evaluation of the Safe and Fuel Efficient Driving scheme (SAFED) for truck drivers found that drivers achieved an average improvement in miles per gallon of around 10%.

  43.  However, further evidence is needed in order to quantify the full range of potential benefits and costs. CCP2006 announced additional funding to provide relevant training and best practice advice for truck and van drivers. This will help provide further evidence as to the level of carbon savings that further extensions to the sustainable distribution programme could deliver.

  44.  Eco-driving in passenger cars will be targeted as part of a new communications campaign to promote consumer information on buying greener vehicles and driving in a more eco-safe manner. Trials carried out by the Driving Standards Agency suggest eco-driving could reduce fuel consumption by around 8.5%, though no estimate of carbon savings has been made.

G.  The research findings DfT has on carbon emissions from high speed rail as opposed both to conventional rail and short-haul planes

  45.  Looking at the feasibility and affordability of a north-south high-speed link (HSL) is a manifesto commitment. The government has committed to take this forward in the development of a long term strategy for the railways, drawing on Sir Rod Eddington's advice on the long-term impact of transport decisions. The rail strategy will be published in summer 2007.

  46.  The Department is building on current understanding of the relationship between train speed and carbon emissions through:

    —  participating in a train energy measurement study co-ordinated by the Association of Train Operating Companies (ATOC) and the Institution of Mechanical Engineers (IMechE). The study is monitoring in detail the energy consumption of a range of trains to deliver a more robust understanding of how energy is used. The outcome should help to inform future train design as well as giving train operators a clearer understanding of how they can save energy through, for example, better driver training or improved maintenance.

    —  leading the project to secure a replacement to the successful High Speed Trains (Intercity 125s). A key project objective is to ensure the successor train is as fuel efficient as possible both to reduce carbon emissions and operating costs. Therefore, an important element of the appraisal process will be to model the environmental impact of different train specifications, including the impact of speed and higher acceleration on carbon emissions.

    —  reviewing emerging research such as the paper by Professor Roger Kemp of Lancaster University to the IMechE in July 2004[3] comparing the relative energy consumption of different transport modes including car, plane and two hypothetical high speed trains running at 225 and 350 km/h respectively.

H.  Why the Government has decided, at least provisionally, to adopt a multiplier of only 2 on the carbon to reflect the other contributions of aviation to global warming in its carbon offsetting, rather than 2.5 (used previously by HM Treasury), or 2.7 (most commonly used around the world), or some other figure.

  47.  Government is proposing the use of a multiplier as the most appropriate means to include non-CO2 impacts within the offsetting scheme. Note that the adoption of a simple empirical multiplier for aviation should not infer that a linear relationship exists between climate forcing and carbon dioxide emissions.

  48.  In essence, the use of such a multiplier, whilst being a well-intentioned attempt to capture the non-CO2 forcing, can only provide an approximation to the impact of non-CO2 impacts. However, the Government believes that a multiplier is the only feasible and practical way to address non-CO2 impacts within what is a voluntary scheme where there is an emphasis on minimising the administrative burden from elaborate data collection.

  49.  The original and previously most widely supported work relating to the non-CO2 impacts of aviation is that of the IPCC in 1999, which suggested a reference factor of 2.7. This factor was used in the calculation methodology to offset emissions from the 2005 Presidencies of the G8 and EU. The multiplier of 2.5 was used in a March 2003 joint report by HMT and DfT on "Aviation and Economic Instruments" to estimate the climate change related external costs of aviation.

  50.  More recent research: Trade-Off in 2000[4] updates the estimate of carbon dioxide forcing to the year 2000 and improves the accuracy of the impact assessment, resulting in a factor of 1.9. This report was not published until July 2005, too late for incorporation into the G8 and EU Presidency offsetting calculations which were already committed to the IPCC 2.7.

  51.  In order to reflect the most recent and robust scientific evidence currently available, Government has therefore decided to recognise the more recent TradeOff work and use a multiplier of 2. The multiplier of 2 has been adopted for the Government Carbon Offsetting Fund.

  52.  This decision will be kept under review as further scientific evidence becomes available. More widely, the adoption of a multiplier for carbon offsetting should not be taken to set any precedent or prejudice future decisions over the best instrument or mechanism for accounting for non-CO2 emissions from air transport within the EU Emissions Trading Scheme.

I.  The calculation of carbon savings from the fuel duty escalator of 1.9MtC in 2010 in CCP 2006—how are these worked out, and what exactly do they mean, given that it was discontinued in 1999?

  53.  We compared the impact that the fuel duty escalator between 1993-99 had on demand to the impact on demand that revalorisations in fuel duty between 1993-99 would have had. It was found that due to the fuel duty escalator, demand for fuel in 2010 will be lower and this lower demand equates to a carbon saving of around 1.9MtC in 2010.

  54.  To carry out this analysis we compared the impact that the fuel duty escalator had on demand to what would have happened if the escalator had never been introduced. To do this we needed to compare the impact on demand that the fuel duty escalator had to the impact the alternative policy would have had. For this analysis we compared the fuel duty escalator to revalorisations (increasing rates in line with inflation each year) in fuel duty.

  55.  Therefore, in our alternative scenario instead of fuel duty rising by 3%, 5% and 6% above inflation between 1993-99, we assumed that at every Budget between 1993-99 fuel duty would only have been increased by inflation. We then estimated how much higher demand would have been due to the lower pump prices with this alternative scenario. We then estimated the difference in demand for fuel between these two policies and therefore the carbon emissions that the fuel duty escalator had saved.

J.  The 20 p/litre duty differential on biofuels—does this depend on what blend of biofuels you fill up with? eg do you get this for 5% blend, as well as an 85% blend?

  56.  The 20 pence per litre duty incentive applies only to the biofuel portion of the mix. For example, for a 5% biodiesel blend, 5% of the fuel is taxed at 27.1 pence per litre (ppl) and 95% at 47.1 ppl. For an E85 blend (a mix of 85% ethanol and 15% normal unleaded petrol), the 85% ethanol is taxed at 27.1 ppl with the remaining 15% petrol taxed at 47.1 ppl.

2   Available at: Back

3   Kemp R. J. Environmental impact of high-speed rail. Institution of Mechanical Engineers. Seminar on High Speed Rail Developments, 21 April 2004. Back

4   From the multi-author paper: Sausen R, Isaksen I, Grewe V, Hauglustaine D, Lee D S, Myhre G, Köhler M O, Pitari G, Schumann U, Stordal F and Zerefos C (2005) Aviation radiative forcing in 2000: and update on IPCC (1999). Meteorologische Zeitschrift 114, 555-561. Back

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