Toma de decisiones

10.6.1 The assessment of the impact of HS2 on carbon emissions is covered in the Appraisal of Sustainability (AoS), and was conducted by Booz and Temple Group using data provided from the HS2 demand model. However we have also undertaken further calculations of carbon implications to help us to better understand the sensitivity of these results to key assumptions – and the implications for our conclusions. The results are all set out in the Appraisal of Sustainability and the HS2 Report. However for completeness we report here the methodology used to underpin the analysis that we have conducted. 10.6.2 The conclusion of our analysis, and that presented in the AoS is that HS2 is unlikely to have a

significant impact on overall emissions from transport. There is significant uncertainty surrounding the impact, and the assessment is particularly sensitive to assumptions around the carbon intensity of electricity and the response of the aviation industry as a result of HS2. However even taking this into account, we estimate HS2 will result in somewhere between a small (0.3%) increase in transport

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Emissions from Rail

10.6.3 The impact of HS2 on rail emissions is three fold:

• There would be an increase in emissions as a result of HS2 trains consuming electricity

• There would be a reduction in the number of Pendolinos on the WCML, as these trains are

replaced with HS2 trains

• However the additional trains used on the released capacity would result in additional emissions

from both electricity, and a small number of diesel trains.

10.6.4 The energy consumption of HS2 trains has been modelled explicitly using information on the line of route including speeds and acceleration patterns, gradients, tunnels. A train running along the length of the line consumes around 4.4MWh (Megawatt hours), which is equivalent to 25 KWh (Kilowatt hours) per km.

10.6.5 For classic compatible trains running beyond the high speed line, their performance is assumed to be comparable to that of a 9-car Pendolino. A recent energy metering trial suggests this is equivalent to 14.3KWh per train km. This suggests that HS2 trains – both HS captive and classic compatible fleets - will consume just over 850GWh (Gigawatt hours) per year. To offset this, we estimate there would be a reduction of around 5.4m train kilometres travelled by Pendolinos, saving some 77GWh per year.

10.6.6 To convert this to carbon emissions requires an understanding of the carbon intensity of electricity. This is a key assumption, but is also highly uncertain. The carbon intensity currently stands at just

over 0.5kgCO2 per KWh. However it is expected to decline significantly in the future. Government

projections suggest it should fall to just under 0.4kgCO2 per KWH by 2025, but beyond this there is

no firm commitment.

10.6.7 In practice carbon intensity is likely to fall further if the UK is to achieve its targets on climate

change. The Committee on Climate Change has suggested it will need to fall to less than 0.1kgCO2

per KWh by 2050 to achieve the targets set out in the Climate Change Act. However since this is not current government policy we have been relatively cautious in our central case. We have applied a

factor of 0.385kgCO2 per KWh, but have applied a wide range to this assumption. The upper bound

is today’s emissions levels, but at the lower bound HS2 could (at least in theory) be supplied entirely from renewable sources. This is likely to be an extreme assumption but is the theoretical limit of emissions.

Chapter 10: The Overall Business Case for HS2

10.6.8 On the basis of these assumptions we estimate

• HS2 trains will emit around 0.33 MtCO2 (Million tonnes of Co2) per year (within the range 0 to a

0.43MtCO2 increase in emissions per year);

• The reduction in Pendolinos will save 0.03MtCO2 per year (within the range 0 to a 0.04 MtCO2

saving per year);

• The re-use of capacity will increase emissions by 0.02 MtCO2 per year (within the range of an

increase of 0.01 to 0.02 MtCO2 per year).

10.6.9 The increase in emissions from trains used for released capacity has been estimated using data from DfT’s NMF model which estimates the average emissions per km of electric and diesel trains on the classic network. This does not as standard report energy consumed, but has been adjusted to allow different assumptions on carbon intensity of electricity. At the current level of carbon intensity

of electricity, this model suggests the average train emits just over 5kgCO2 per train km, which

forms the starting point for the range of impacts above.

Mode shift from road

10.6.10 HS2 would deliver a reduction in road journeys, particularly on key routes from Birmingham and Manchester. Our demand model estimates there will be almost 22 million fewer car km in 2033 as a result of HS2. This could reduce carbon in two ways:

• The reduction in car trips results in a direct reduction in emissions as that journey is undertaken

on HS2;

• Reduction in congestion speeds traffic up, which would have an indirect effect on cars that

remain on the road network. This generally improves fuel consumption (and reduces emissions), although in some cases the opposite is true.

10.6.11 We have not calculated the impact of the latter. Given the scale of change in road km (less than 1% of all car km in 2008), congestion effects are unlikely to have significant impacts on fuel efficiency. 10.6.12 WebTAG provides estimates of fuel consumption depending on the mix of cars (petrol/diesel) and

the speed the car was travelling at. This can be converted into a range of emissions per car km –

ranging from 0.4 kgCO2 per km at low speeds, through to 0.16 kgCO2 per km at just over 60mph. This

means the reduction in carbon emissions as a result of mode shift from car is within the range 0.002

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Mode Shift from Air

10.6.13 The impact of mode shift from air is the single biggest uncertainty in our estimates of carbon emissions. The HS2 demand model suggests that HS2 would lead to around 11% fewer domestic air passengers. However this in itself does not deliver a reduction in carbon emissions. It is how the airlines respond to this change in demand that would determine the impact of HS2 on aviation emissions.

10.6.14 Airlines could respond by reducing service frequencies, or flying smaller planes. They could even respond by withdrawing routes altogether, perhaps with the opportunity of ‘code sharing’ with HS2 (as, for example, Air France do on routes to Brussels). Alternatively they might not respond at all – choosing to maintain current service levels in order to maintain a service for interlining passengers (who tend to be higher value customers for airlines).

10.6.15 We have estimated a range of emissions reductions based on:

• Airlines respond by reducing the size of planes and frequencies such that emissions per

passenger are maintained. Thus the 11% fall in air passengers would reduce domestic aviation

emissions by the same proportion. Based on data of domestic aviation emissions18 _{this is}

equivalent to a reduction of around 0.4MtCO2 per year in 2033.

• Airlines do not respond at all, and there is no reduction in aviation emissions as a result of HS2.

10.6.16 We have not considered in this range the potential for airlines to re-use slots freed up at airports as a result of a reduction in the number of domestic flights. If airports slots are re-used for flights to new destinations, then this would have implications for the emissions from aviation.

Summary of HS2 Carbon Impact

10.6.17 The impact of HS2 on UK carbon emissions is uncertain, and highly dependent on assumptions of the carbon intensity of electricity which the scheme uses, and of the response from airlines to changes in passenger numbers as a result of HS2. Despite this, it would seem that the impact of HS2 on UK carbon emissions is likely to be small. We estimate that this impact is equivalent to a range of -0.3% to +0.3% of all UK transport emissions. Our central estimate is a net reduction in

emissions of less than 0.1MtCO2 (less than 0.1% of UK transport emissions). This suggests HS2

would not be a major factor in managing carbon in the transport sector.

Chapter 10: The Overall Business Case for HS2

10.7 HS2 Value for Money