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Rail’s carbon footprint

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Does carbon matter to rail? This was the question posed at a recent seminar hosted by the Institution of Mechanical Engineers (IMechE). Delegates from across the rail industry gave their response, presenting a mixed message on how the UK’s railways need to adapt to reduce their carbon footprint … or not.

When it comes to green credentials, or to be more specific, the size of its carbon footprint, the UK’s railways have a pretty good start. Let’s try to put it into context. The UK churns out 520 million tonnes of carbon dioxide (CO2) annually. That sounds a lot, and it is, but on the global scale it’s a relatively minor amount. In the league of carbon producers, China takes the lead with 7,711 million tonnes per year, followed by the USA with 5,425 million tonnes. By comparison, the UK is a mere ‘also ran’, accounting for just 1.7% of the total world output. Roughly 25% of the UK’s carbon output can be attributed to transportation and rail is responsible for just 1.8% of that. Without becoming too much bogged down with the figures, suffice it to say that the UK rail network accounts for about 0.0076% of the world’s CO2 production. So, in terms of carbon, is rail a problem, or might it provide a solution?

Published targets

As part of the Kyoto agreement the EU has set targets for the reduction of greenhouse gasses (GHG) – mainly CO2. For 2050, the EU objective is to reduce Europe’s GHG emissions by 80-95% compared to 1990 levels. The Climate Change Act 2008 reinforces this – indeed goes beyond it – and the UK is committed to a 34% reduction in GHG emissions by 2020 and 80% by 2050.

The objective is to offset the massive increases in emissions from developing industrial countries such as China, India, Brazil and others. The EU says that developing countries have a right to develop. In China, emissions are up 170% since 2000, but there can be no limitation until GDP per capita (the value of goods produced per person) reaches $25,000. Currently, it is £5,000.

Meanwhile, car ownership is rising and China plans to build another 363 coal fired power stations. India plans to build 455, the worldwide figure is something like 1,200 and, as is common knowledge, greenhouse gas emissions have been linked to global warming and climate change.

Although the UK has been cutting emissions at home, it imports goods that produce CO2 in these other countries, pushing up emissions from there. The UK is the second highest importer in the world of these so-called ‘embodied’ emissions. Bearing that in mind, strong action is needed in transport if the 2030 and 2050 targets are to be met: transport is the only sector in which GHG emissions have risen since 1990 (by 19% overall). The European Commission’s strategy for meeting the 2050 reduction goal in transport was set out in the 2011 Roadmap to a Single European Transport Area – Towards a Competitive and Resource Efficient Transport System (the ‘Transport White Paper’).

Cleaner transport

A key point in the Roadmap for all transport modes is that transport needs to use less energy and to use cleaner energy. Future development in transport must rely on improving the energy efficiency performance of vehicles and developing and deploying sustainable fuels.

It is recognised that standards are needed for CO2 emissions of vehicles in all modes, supplemented by requirements on energy efficiency where necessary. Significantly, energy use reduction goals are to be considered for cars, road freight, and aviation – but not for rail!

Specific Roadmap targets for the rail sector are: » Facilitate ‘efficient and green freight corridors’;

» Triple the length of the existing high-speed rail network by 2030, and complete the network by 2050;
» By 2050, the majority of medium-distance passenger transport should go by rail.

In terms of carbon emissions, rail movement is somewhere between two and five times more energy efficient than road transport. Rail’s share of transport GHG emissions is 2%, while rail’s market share is 6% (passenger) and 10% (freight).

Modal switching in favour of rail therefore seems to make sense. In fact, it is an important part of emission reduction strategy. The target is to shift 30% of road transport over 300km onto rail by 2030, and 50% by 2050. Through maximising use of existing infrastructure alone, a 30-40% growth in train- kilometres by 2020 could be accommodated. Taking into account projected demand for 2020, rail freight traffic could still grow by
28% and passenger transport by 38% over the whole European network.

There is particular scope for rail to increase its market share in certain segments such as international containerised transport. In freight transport, up to 20 million tonnes of CO2 (7% of freight transport emissions) could be reduced by modal shift of traffic from road to rail by 2020.

Electrification is the answer

The de-carbonisation of the EU’s electricity supply is targeted for 2050 – although how this will be achieved isn’t fully explained.

With full electrification of the rail network, rail transportation can therefore be fully decarbonised. With other transport modes, such as road and air, this is clearly not possible. Decarbonisation offers obvious opportunities for rail – but the rail sector needs to develop the capacity and ability to meet the challenge.

Some 80% of total European rail traffic already travels on electrified lines. In the UK, only 35% of the network is electrified although it carries 55% of passenger journeys. At the same time, other transport modes are becoming greener. Improving efficiency within the road sector is reducing GHG emissions and narrowing the gap with rail.

The rail sector therefore must continue to improve efficiency in order to retain its low-carbon advantage. It must also develop capacity to absorb new traffic as a result of modal shift. As Libor Lochman, executive director of the CER (Community of European Railway and Infrastructure Companies) put it: “The rail sector is in a strong position to both contribute to, and benefit from, the decarbonisation of transport.”

To ensure maximum benefit it must:

  • »  Actively support EU transport policy goals;
  • »  Set targets in electrification and high speed lines to accommodate growth and modal shift;
  • »  Make further improvements to retain advantages over other transport modes;
  • »  Articulate and communicate its case – publicising the low carbon strengths of rail and use marketing to make rail more attractive.

In order to persuade car users to leave their cars behind, the rail sector needs faster services, more comfort, less crowding and lower fares. And how about easy parking and reduced parking charges at stations? Not least, the trains and infrastructure need to be reliable and efficient.

Urban rail

Ian Walmsley is engineering development manager for Porterbrook. He also examined what he sees as the biggest opportunity for rail, namely the reduction of urban road congestion by means of trams and metro systems. The CO2 figures certainly stack up. In terms of CO2 grammes per passenger kilometre, the figures he presented were as follows:

  • »  Car – 151
  • »  National Rail – 65.1
  • »  Tram – 80.9
  • »  London Underground – 83.3
  • »  Coach – 36

Importantly, these figures have to be adjusted for load factor effect. Many trains, for instance, could accept more passengers. Service increases would be targeted at reducing road traffic where it is least efficient. With a high load factor, rail can achieve 50g/passenger.km, giving a modal transfer saving from private cars to rail of 100g/ passenger.km. According to Ian Walmsley, the rail sector needs to assert its carbon credentials, actively promote modal transfer and plan for double the number of passengers.

New technology

So in what ways can rail become more efficient in terms of energy usage and reduction of GHG emissions? In his opening address, Professor Richard Parry-Jones, Network Rail chairman, outlined them. Longer and more frequent trains with greater reliability would clearly be a help. Technical  advances will contribute too, such as intelligent traffic control, driver advisory systems (as recently introduced by First Great Western), lighter train body shells and optimised regenerative braking. Aerodynamics too will be given greater attention in train design.

Saving energy, and therefore GHG emissions, in these ways will present interesting challenges to engineers, but there is an opposing view. It was outlined by Iain Flynn, lead sponsor train systems and upgrades, strategy and service development, London Underground (LU). As he put it, “There is an inconvenient truth. No matter how we cut the numbers, delivering more capacity is the key priority. This means greater energy consumption – mostly it makes sense to run our trains flat out.”

On London Underground, energy consumption is 80-90% for traction. “Lighter trains don’t help much either,” said Ian. LU’s electric trains are already remarkably efficient, although the need for air conditioning makes the energy situation worse. Here, the real issues are modal shift and economic growth that LU’s services facilitate.

Year on year, LU needs ever more capacity, which means more energy. What goes in tends not to come out, so the net effect is that the deep tunnels are heating up. Only the Victoria Line and Jubilee Line Extension have numerous ventilation shafts. Standard upgrades put 25-45% more energy in to give more capacity, resulting in a 2-3°C rise in tunnel temperature. According to Iain Flynn, the cost of removing this heat is three times the cost of the original energy. There is a complex trade-off between capacity, cost of cooling and/or improved efficiency.

Regenerative braking offers the single biggest efficiency opportunity. It works best with newer trains operating on lines with no older trains, although LU is investigating this. The Victoria Line achieves a regenerative braking efficiency of about 35% of the traction energy consumption and the challenge is to get the entire LU network to this level.

Is it worth the effort?

Therein lies the rub. We’ve seen how rail has inherently green credentials and yet it must meet emission targets and save energy. And if UK rail meets its CO2 reduction target of 10% by 2030, what would that mean on the global scale?

As we saw at the start of this article, UK rail presently accounts for 0.0076% of the total world output of CO2. Ian Walmsley has pointed out that a 10% saving would equate to just 14 minutes of China’s output which amounts to 15,000 tonnes of CO2 every minute. It is widely recognised though that it is through modal shift that rail offers one of the best ways of reducing CO2 emissions. To accomplish that there needs to be an incentive in persuading people out of their cars and getting long haul freight off the roads.

Energy saving methods are well and good (some would say vital) and they are being embraced, but if the bottom line (rail fares and freight charges) become loaded as a result, that is not good. If our railways were to become more accessible, more efficient and yet less green, would that be a bad thing? Surely the overall effect would still be to the common good – an overall reduction in CO2 emissions for transportation. Perhaps road and rail should be considered together?

So does carbon matter to rwwail? The answer seems to depend on your point of view. Certainly the effects of climate change matter to rail, as we have seen recently. What if we were to turn the question around and ask, does rail matter to carbon? The answer then has to be no, but if and when the CO2 reduction targets are met, at least we’ll have an efficient, electrified railway network that costs a lot less to run. And there will be fewer cars on the road… maybe.

Stuart Marsh
Stuart Marshhttp://therailengineer.com

New and innovative technology, signalling (particularly on narrow gauge and industrial networks), telecommuications and fibre-optics

Stuart Marsh has had a lifelong interest in railways, especially in railway signalling. He blames this on his grandfather and uncle, who were both railway signalmen.

However, having graduated from Bangor University with a Joint Honours degree, Stuart decided to pursue a career in business. He now finds himself the owner and Managing Director of two companies. Highblade Cables, which he started in 1985, produces cables, wiring looms, fibre optics and racking hardware for the electronics, telecommunications and data communications industries. Thirty years later his business is still going strong.

Unable to keep away from railways, Stuart has worked for many years as a volunteer signalling technician on several heritage lines. This outlet for Stuart's skills in electrical and mechanical engineering led eventually in 2008 to the formation of his second manufacturing company.

Signal Aspects Ltd designs and produces specialised and bespoke signalling equipment, mainly for minor and industrial railways. Its products include LED signal lamps, route indicators, train detection equipment and electric point machines. Indeed, it was his development of a new point machine, designed specifically for narrow gauge railways, that led to his debut article for Rail Engineer magazine.

Stuart has since become a regular contributing writer, covering a host of topics ranging from the capture of newts to major resignalling schemes.


  1. Great article Stuart, thanks for your broad and insightful overview of the issues. But I’m baffled by your conclusion, does rail matter to carbon? The answer must be a massive yes, because a low carbon transport system is either limited to the range of a push bike, or is built on (electric) rail and (sail assisted electric) ship. The emission figures are clear, there are really no other options.


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