Railways were there at the start of the process that set us on the path to climate crisis. Steam-powered engines helped fuel the first industrial revolution, giving Britain easy access to cheap coal.
But today they’re at the forefront of innovation in more sustainable transport, and will be an essential part of our response to the environmental emergency. Read on to find out about some of the developments that offer paths to greener, more sustainable transport.
Railways, coal and industry
Coal and railways have always been closely connected. Britain developed the railway system from its background in mining technology, using rails to transport coal from mines to waterways where it could be shipped. Railways enabled a fourteen-fold increase in coal production between the 1550s and the 1680s. Into the 18th and 19th centuries railway development drove technical innovation in steam powered-engines fed by coal, and these engines ran on British Rail until 1968 and as late as the 1980s in a few collieries.
Today, however, railways are seen as part of the solution to sustainable transport, because the way they work still offers a key advantage. Railways help overcome friction, requiring less energy to move heavy goods or large numbers of people than with a road-based system.
But rail transport accounts for a very small percentage of global carbon emissions from transport—just 1%, compared to 45% from passenger road transport. If we are going to drive and fly significantly less, railways need to be both resilient to climate change and able to operate at a much higher capacity.
Climate emergency and the modern British rail network
Average global temperatures have risen by more than 1°C since the 1850s, and the years 2015–2020 were the hottest ever recorded. The Met Office projects that as a result of climate change the UK will see warmer and wetter winters, hotter and drier summers, and more frequent and intense weather extremes. This will all have an impact on the running of railways.
Floods, heat and weather emergencies
Climate change is already taken into account when planning for the UK’s rail network. Network Rail established a Weather Resilience and Climate Change adaptation programme in 2014, publishing a strategy in 2017 which aims to ensure 'a railway that is safe and more resilient to the effects of weather'.
The need to prioritise resilience to extreme weather makes sense when you consider that a recent Network Rail survey suggested 40% of the UK’s track miles are in areas of medium to high flood risk.
Flooding has of course been a problem for railways for a long time, but the frequency of flood events has increased, requiring costly alleviation measures. In 2020, for example, a railway junction near Exeter had new flood prevention measures put in at a cost of £26 million. In the same year flash flooding near Stonehaven caused a landslip which derailed a train; three people were killed. In Scotland, the West Coast Main line was closed for a month in 2015 after storm ‘Frank’ caused the viaduct at Lamington to suffer major structural damage to the point where it was near collapse.
In contrast, summer heat forces trains to slow down, because high temperatures can cause rails to buckle and lead to derailment. On hot days the temperature of the rails can be as much as 20 degrees hotter than the surrounding air temperature. Rails are normally stress tested at 27 degrees centigrade, the mean summer temperature, to prevent buckling—but this figure may have to increase to as much as 40 degrees as the climate changes. Some rails are already being painted white to reflect some of the sun’s glare.
As well as alleviation works on existing routes, lines closed under the Beeching cuts in the early 1960s are being reopened, such as the Southern Railway line to Okehampton, the 'Borders' railway from Edinburgh to Tweedbank and London Marylebone to Oxford. More access to rail services reduces car dependency, thereby bringing down carbon emissions from road transport. Reopened routes also give flexibility to the freight train network.
Then there's HS2, which is under construction and will release capacity for freight and passenger trains on the classic routes, while also reducing demand for regional air services, as the high-speed lines throughout the world have been shown to do since the first Shinkansen line opened in Japan in 1964.
Work to make the rail network more resilient and the reopening of railways where it makes economic sense are important parts of the current rail story as the industry responds to the climate emergency.
Routes to decarbonising rail travel
While future-proofing the infrastructure of the UK rail network to help it cope with the climate emergency is vital, other players in the rail industry are looking at how to power trains more sustainably.
One of the key ways forward is electrification, powering trains with electricity generated from renewable, sustainable sources. Besides moving away from fossil fuels, rail electrification also means trains can be slowed using regenerative braking which puts power back into the network, a proven possibility on electric railways since the 1880s.
Today about 38% of the UK network is electrified compared with 61% of the German rail network. Both countries plan to run 100% of train kilometres by electric train or climate-neutral power by 2050. The UK government plans to rule out diesel trains after 2040, an ambitious target given the lack of a rolling programme of electrification. But there are hopeful developments in the Netherlands, where 75% of the rail network is electrified—and since January 2017 all those trains have been powered by energy from wind turbines.
While the UK is yet to catch up with this level of rail electrification or ‘green’ energy, it’s already the leader in offshore wind. In 2019 the UK developed the world’s first floating wind farm, Hywind Scotland, building on the engineering expertise of the North Sea oil industry but in a renewable direction. Offshore wind power is more consistent than onshore, and giant wind farms like the one at Dogger Bank—planned to deliver 5% of total UK demand by 2026—will be vital to producing enough green electricity in the future.
While most electric railways in the world get their power from overhead lines using AC electricity, in the UK a large number of former Southern Railway lines use the third rail system, which runs on DC. Instead of cables overhead, power is supplied via a third conductor rail running along the side of the track. The downside of this system is that it needs more current top-ups, because the third rail is an inefficient conductor—it was originally developed as a cheaper system to use at a time when transmission losses between the power station and the train seemed less important.
In 2019 an experiment near Aldershot (where electric trains use the third rail system) was directly powered by energy from a solar farm for the first time, helped by the fact that the power output of the solar installation is similar to that of the trains.
The potential for solar energy is large, and Britain’s railways have many places where fitting solar could make sense—particularly station and depot roofs. One company has even proposed putting solar panels on railway sleepers—an innovative idea, but one which would greatly complicate essential track maintenance, since there are around 2,400 railway sleepers in a mile of track and over 10,000 miles of track in the UK.
What are the alternatives to electric railways?
There are situations where you can’t easily electrify a railway—for example, if the cost of new infrastructure is too high. So apart from renewable electricity, what other options are there to help decarbonise rail transport?
Green hydrogen power
One alternative—first demonstrated on a miniature railway in 2012—is to have a locomotive powered by a hydrogen fuel cell, so long as the hydrogen is carbon-neutral, produced using renewable energy. This kind of train wouldn't need the investment in new infrastructure that electrifying a railway requires.
A standard gauge train using hydrogen technology went into service in Lower Saxony in Germany in 2019. The UK’s first standard gauge hydrogen-powered train, 'Hydroflex', was demonstrated at Rail Live the same year, and has been followed by other projects in the UK, including a similar development in Scotland.
A fleet introduction is planned for hydrogen-powered trains on the Bishop Auckland to Teesside/Middlesbrough lines by 2025 as part of the Tees Valley Multi-Modal Transport Hub. The rail network in the Tees Hub includes part of the Stockton and Darlington Railway—originally built to transport coal almost 200 years ago. This project relies on sustainable hydrogen creation and will see Class 321 trains converted to hydrogen/hybrid power, using hydrogen fuel cells when not on electrified lines.
Batteries included: hybrid models
The other alternative is the battery hybrid, which can travel a long way down a branch line on a fast charge battery alone, and is also capable of regenerative braking. This has been proposed for the Windermere branch of the West Coast Main line and has potential for a number of other branch lines where the cost of normal electrification is considered too much, and green hydrogen is not easily available.
Rapid recharging has made these types of trains attractive for relatively short lines, and they enable the benefits of an electrified railway beyond lines with existing infrastructure. The latest train of this kind—an ‘upcycled’ London District line train—was demonstrated in June 2021. As in many fields, using existing materials to recycle in this way is much cheaper than specifying and building a locomotive from scratch.
Greener freight trains
Aside from passenger trains, freight is also important to consider in terms of sustainable transport—every ton of freight on the rails reduces carbon emissions by 76% compared to road haulage. Rail freight removes the need for about 7 million lorry journeys a year at current volumes.
However, the sheer power needed to move a heavy freight train creates problems for locomotives not using conventional diesel or electric power. For example, the fuel tank of a typical freight loco in the UK contains about 19.8 MWh of energy. By contrast, the battery of a class 379 passenger train has about 0.5 MWh of energy. This vast difference highlights the challenges of moving away from diesel, pointing again to the need for more electrification.
Options being trialled include a biogas and hydrogen dual-fuel conversion of an existing class 66 locomotive, and the conversion of the long-serving 08 shunter to battery power with a hydrogen fuel cell to keep the batteries fully charged. It seems that familiar-looking trains will be on the network for many years to come, even if their prime mover has changed.
Planes, trains and automobiles: The future of green transport
There are other developments and experiments underway, from carbon capture to ammonia-powered fuel cells, all of which point to some serious work by companies, universities and government towards decarbonising the rail sector. This will also be good news for travellers, making stations cleaner and quieter.
While it's likely that rail (ordinary trains as well as trams and other light rail) will play a bigger role in future sustainable transport, the major challenge is decarbonising road transport, which accounts for vastly higher carbon emissions than rail. Railways need continued innovation so they can provide a viable, sustainable alternative to the road transport sector, and help us move towards carbon-neutral travel.
Find out more
- Our World in Data, CO2 emissions from transport
- Network Rail, How third rail works
- University of Birmingham, Rail decarbonisation
- Carbon Brief, How 'aggressive' railway expansion could cut emissions