The high-speed rail project has become one of the most costly and controversial of the modern era – and may not even be good for the environment

One of the principal arguments in favour of HS2 was the positive effect it would have on the environment – and this was rooted in the belief that high-speed electric trains could help the UK cut its carbon emissions.

Fears grow over HS2's potential impact on biodiversity Read more

The rail project, supporters have argued, will lessen demand for carbon-intensive air travel, road freight and car journeys by linking northern England – and potentially Scotland – with the Midlands, London and HS1 to the Channel tunnel and continental Europe.

Providing low-carbon alternatives is urgently needed because transport (mostly road) is now Britain’s largest greenhouse gas emitting sector, accounting for 28% of all GHG emissions in 2017.

The government has a target of net zero emissions by 2050, but there is disagreement over whether HS2 will really help deliver.

Fears grow over HS2's potential impact on biodiversity Read more

At face value, the project should be a good way to cut carbon.

Electric trains, particularly if powered by renewable energy, provide low-carbon transport. HS2 claims it can achieve 8g of carbon emissions per person per km. The same journey by car would generate 67g of emissions – and by plane, 170g.

But carbon modelling – predicting a new infrastructure’s carbon emissions – is, like all future-gazing, imprecise and dependent on computer modelling.

The government’s own calculations for HS2 suggest its carbon emissions could exceed potential savings, even over the railway’s projected 120-year lifetime.

HS2 will not cut carbon emissions. According to HS2’s own forecasts, even over 120 years, its overall construction and operation cause carbon emissions of 1.49m tonnes of carbon dioxide equivalent. This represents just 1.18% of Britain’s annual transport emissions, but critics say it is still an increase when emissions need to be falling rapidly to reach net zero.

HS2’s construction requires vast quantities of concrete and steel, as well as diesel-powered machines moving millions of tonnes of earth.

A 2019 report for the High Speed Rail Group (HSRIL), which represents companies with an interest in high-speed rail, estimates construction could be reduced by 20% to 30% with low-carbon innovations, such as hydrogen-powered floodlights and hybrid excavators.

HS2’s calculations show its emissions will be offset by the wider decarbonisation of transport it helps create. Some road freight will move to rail as HS2 will enable the wider rail network to take more freight.

There will also be a “modal shift” – people choosing to travel by HS2 instead of driving or flying – but this is likely to be small. The Department for Transport suggests only 1% of HS2 passengers will be people who would have flown, and 4% those who would have driven.

Some analysts argue that HS2 has presented an overly pessimistic carbon-saving forecast because it is obliged by law to give worst-case scenarios.

The HSRILG report points out HS2’s forecasts of 4% and 1% are based on assuming that driving and flying become more affordable while rail fares increase above inflation.

In practice, the European average for high speed rail modal shift is 15% from cars and 30% from planes. Furthermore, HS2’s forecasts do not include carbon-saving from increased use of local passenger rail, with HS2 freeing up lines such as the west coast mainline to provide better local services.

Julia King, the deputy chair of the committee on climate change, reviewed HS2’s carbon forecasts for Tony Berkeley’s minority report on HS2 and judged them “sensible and conservative” – they do not include highly speculative future scenarios, such as HS2 leading to fewer new roads. If HS2 was well integrated with the European high speed network (and critics say it is not, because it does not connect to HS1) it could become part of a European-wide system saving up to 5m tonnes of carbon dioxide equivalent by 2050 if all journeys under 1,000km moved to rail.

Quick guide HS2's carbon balance sheet Show Hide Potential emissions Construction: • Huge quantities of steel and concrete including concrete slab-track • Moving construction materials to site • Tunnelling (more carbon-intensive than open-air construction) • Construction machines • Removing soil by truck • Manufacture of rolling stock • Journey to work of HS2 employees Operation: • Power source not guaranteed to be renewable. Speed of HS2 requires more power • Ongoing maintenance • Increased car journeys to HS2 stations • HS2’s better airport connections could increase flying • Domestic flights reduced by HS2 could lead to increase in international routes Potential savings • Increased rail capacity shifts freight from road to rail • Increased capacity leads to more local/regional rail journeys • Modal shift with travellers choosing rail over more carbon-emitting road • Travellers also switching from flying to high-speed rail • Carbon sequestration from tree-planting • HS2 could be powered by all-renewable energy • HS2 prevents other carbon-intensive infrastructure projects Sources:

HS2 Limited, 2019, High Speed Two phase 2a, Informationa Paper, E27: carbon Friends of the Earth, Opportunity Costs of HS2, 2019 Lord Berkeley’s Dissenting Report, 2020 [Size of emissions not included because different scenarios give different estimates; figures have not been modelled for all these factors]



But Lord Berkeley and other critics argue there are risks that HS2 could increase emissions. More people might drive to HS2 “parkway” stations. And by connecting airports more effectively in London, Birmingham and Manchester, HS2 could lead to an increase in flights. If HS2 cuts demand for domestic flights, says Friends of the Earth, that could simply encourage the aviation industry to switch domestic flight slots to more profitable, and carbon-intensive, international routes.

HS2 could be made less carbon intensive. Critics such as Berkeley point out that if HS2 was not built to such a high specification (with top speeds supposedly in excess of continental high speed rail), emissions would be reduced both in operation and construction; it wouldn’t require carbon intensive concrete slab-track, for instance.

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An independent report by the rail consultants Greengauge in 2012 said HS2’s sustainability would be maximised by reducing its top speed, fully using freed-up capacity on the existing rail network, and creating city-centre stations rather than edge-of-town parkways. Supporters claim HS2’s plans for parkway stations are already morphing into “sustainable urban extensions” with high-density housing and tramways.

Ultimately, HS2’s future emissions will depend on wider – and more joined-up – transport and energy policies. It would use less carbon if there was a decarbonisation of electricity supply (rather than another dash for gas), and coherent national policies to reduce car use and air travel.

Friends of the Earth and other critics highlight the “opportunity cost” of HS2: its £106bn price (at least £5bn a year for 20 years) will lead to less investment in more effective carbon-saving transport, such as regional rail, buses, cycling and walking. Berkeley concluded that electrifying existing railways would have a much greater environmental benefit. Friends of the Earth suggest an even less glamorous low-carbon option: making all UK buses free would cost £3bn a year.