Trains: Reducing Air Pollution, A Greener Travel Option?

Transport is a major contributor to global warming and air pollution. With aviation contributing about 2% of the world's carbon emissions, many people are now considering alternative modes of transport, such as trains, to reduce their carbon footprint. But does travelling by train really reduce air pollution?

The answer is yes, but it's complicated.

The environmental impact of travelling by train vs plane or car

Plane

Flights produce greenhouse gases, mainly carbon dioxide (CO2), from burning fuel. These gases contribute to global warming when released into the atmosphere. According to the International Civil Aviation Organization (ICAO), an economy-class return flight from London to New York emits an estimated 0.67 tonnes of CO2 per passenger. This is equivalent to 11% of the average annual emissions for someone in the UK. Aviation contributes about 2% of the world's global carbon emissions, and this is predicted to rise as other sectors of the economy become greener.

The emissions produced by a flight depend on various factors, including the class of travel, the number of passengers on the plane, the length of the flight, and the height the plane reaches. For instance, carbon emissions per passenger per kilometre are about three times higher for business class and four times higher for first class on long-haul flights. Taking off uses more fuel than cruising, so shorter flights account for a larger proportion of fuel usage. Private jets emit fewer emissions overall but more per person.

Train

According to two transport and environment studies published by the European Environment Agency (EEA), train travel is the most environmentally friendly mode of motorised passenger transport in Europe when compared to travelling by car or plane. However, the carbon footprint of train travel depends on factors such as the type of train, the class of travel, and the number of passengers. For electric trains, carbon emissions are calculated based on the way the electricity they use is generated. Diesel trains' carbon emissions can be twice those of electric trains. For example, some diesel locomotives emit more than 90g of CO2 per passenger per kilometre, compared to about 45g for an electric Intercity 225.

The source of the electricity used by electric trains also matters. For instance, in France, about 75% of electricity comes from nuclear power, while in Poland, about 80% of grid power is generated from coal. The number of passengers on a train is also a factor, as a peak-time commuter train will have much lower emissions per person than a late-night rural one.

Car

Travelling by car can be more environmentally friendly than flying, depending on the type of car and the number of passengers. Electric cars are generally better for the environment than diesel or petrol cars. However, driving any kind of car with just one passenger will emit much more CO2 than getting the train. On the other hand, driving a fully packed low-emission or electric vehicle can result in lower emissions per person than travelling by train.

Boat

The environmental impact of travelling by boat depends on various factors, such as the age and efficiency of the vessel. Ferries emit less CO2 per passenger kilometre for a foot passenger than for a driver and car. Cruise ships fall into similar territory to flying in terms of emissions.

The carbon footprint of train travel depends on factors like class and type of train

The carbon footprint of train travel depends on several factors, including the class of travel and the type of train.

Firstly, the class of train ticket can affect the carbon emissions per passenger. For instance, business-class train tickets tend to have higher emissions per passenger as these carriages have fewer seats, meaning each passenger accounts for a larger proportion of the train's pollution.

The type of train is also a significant factor. Some of the most energy-efficient trains, such as the Eurostar, produce around 6g of CO2e per passenger kilometre. In contrast, more polluting trains, like national rail services that rely on diesel power, produce an average of 41g of CO2e per passenger kilometre. Diesel trains' carbon emissions can be twice those of electric trains. For example, diesel locomotives can emit over 90g of CO2 per passenger kilometre, compared to about 45g for an electric Intercity 225 train.

The source of electricity for electric trains is another consideration. Countries with greener energy mixes, such as France with its nuclear power, will have lower carbon emissions from electric trains than countries relying heavily on coal, like Poland.

Other factors that can influence the carbon footprint of train travel include the occupancy rate of the train and the environmental impact of rail infrastructure construction and maintenance.

While train travel is generally more environmentally friendly than flying or driving, the specific carbon footprint depends on these various factors, making it important to consider the specifics of each journey when making environmentally conscious travel choices.

The environmental impact of aviation

Aviation has a significant impact on the environment, contributing to climate change and global warming. The industry has been working to reduce its carbon footprint and limit greenhouse gas emissions, but it still accounts for a notable proportion of human-induced CO2 emissions. Here is an overview of the environmental impact of aviation:

Greenhouse Gas Emissions

Aviation contributes to global warming and air pollution by emitting various greenhouse gases, primarily carbon dioxide (CO2). In 2023, air transport generated 882 million tonnes of CO2, accounting for around 2.05% of all human-induced CO2 emissions for that year. This percentage is expected to rise as other sectors of the economy become greener. According to the International Air Transport Association (IATA), aviation contributes about 2% of the world's global carbon emissions, and passenger numbers are predicted to double by 2037.

Other Emissions

In addition to CO2, aircraft engines produce nitrogen oxides, water vapour, unburned hydrocarbons, carbon monoxide, and sulphur oxides. These emissions have a greater warming effect when released at high altitudes. Aviation is the main human source of ozone, a respiratory health hazard causing an estimated 6,800 premature deaths per year. Aircraft engines also emit ultrafine particles, which are health hazards and can increase cardiovascular risk.

Water Pollution

Airports can generate significant water pollution due to their handling of jet fuel, lubricants, and other chemicals. De-icing fluids used in cold weather, for example, can pollute nearby water bodies if not properly contained.

Noise Pollution

Aircraft noise pollution can disrupt sleep, adversely affect children's education, and increase cardiovascular risk for those living near airports.

Alternatives to Air Travel

To reduce the environmental impact of aviation, individuals and organisations can opt for alternative modes of transport, such as train travel, which generally has a smaller climate footprint. A shift from air to rail travel can play a key role in reducing greenhouse gas emissions and achieving sustainability goals.

The impact of public transport on air pollution

Public transport is generally considered to be a more environmentally friendly mode of travel than private transport. However, the impact of public transport on air pollution is complex and depends on various factors.

Train vs. plane

When it comes to air travel, trains are often considered a more environmentally friendly alternative. According to two transport and environment studies published by the European Environment Agency (EEA), train travel is the most environmentally friendly mode of motorised passenger transport in Europe when compared to travelling by car or plane. The studies found that aviation's emission impacts are much higher on a passenger-kilometre basis. However, the margin between train and plane emissions varies depending on factors such as the type of train and the source of electricity used. For example, diesel trains can emit more than 90g of CO2 per passenger per kilometre, while an electric intercity train emits about 45g.

Train vs. car

The carbon footprint of train vs. car travel depends on several factors, including the number of cars taken off the road, the class travelled in, and the type of train and car. In general, driving a car with just one passenger will emit much more CO2 than taking the train. However, driving a fully packed low- or electric vehicle can result in lower emissions per person than travelling by train. Additionally, travelling first-class on a train can double the carbon footprint, as there are typically half the number of seats in a first-class carriage.

Impact of public transport on air quality

Public transportation can only reduce air pollution if it induces a substitution of traffic from roads to public transportation and if it generates less air pollution than road transportation. Studies have shown that expanding regional train services can lead to a reduction in air pollution. For example, a 10% increase in regional train service in Germany reduced carbon monoxide and nitrogen oxide pollution by around 1% and 2%, respectively. This is because expanding rail services can reduce car and motorcycle use, especially for leisure and shopping trips.

Non-exhaust emissions

It is important to consider not only the direct emissions from trains and planes but also the non-exhaust emissions that occur during the production, transmission, and distribution of energy used by these modes of transport. Additionally, transport causes non-exhaust emissions of air pollutants from sources such as the abrasion of brakes, wheels, tyres, and railway tracks.

The impact of regional train services on air pollution

Transportation is a major contributor to air pollution, with road transport being the largest emitter of greenhouse gases in the EU, accounting for 72% of the transport sector's emissions in 2018. To reduce these emissions, a shift from road to rail transport is often proposed as trains are considered a more environmentally friendly alternative. This report assesses the impact of regional train services on air pollution, specifically examining the relationship between rail service improvements and air quality.

Train Services and Air Pollution

Case Study: Germany

A study in Germany examined the relationship between regional train service improvements and air quality. Between 1994 and 2004, the frequency of regional train services increased by 28%, while local air pollution levels decreased during the same period. However, this correlation does not necessarily indicate causation. To address this, the study used a railway reform in 1994 as an instrument, allowing for a comparison between lines procured competitively and those negotiated with the incumbent supplier. The results showed that lines procured competitively experienced stronger growth and greater improvements in air quality, with a 10% increase in rail service leading to a 1-2% reduction in carbon monoxide and nitrogen oxide pollution.

Expanding and improving regional train services can have a positive impact on air quality, particularly by reducing car and motorcycle use. However, the effectiveness of such improvements depends on various factors, including the type of train, passenger numbers, and the specific context. Further studies and policy interventions should consider these factors to maximize the environmental benefits of regional train services.

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