Skytrains: Unseen Pollution And Its Impact

Skytrains, or overhead monorails, are often touted as a more environmentally friendly mode of transportation than road vehicles. While electric trains are generally more energy-efficient and have a lower carbon footprint than cars, it's important to note that they still contribute to pollution. The type of energy consumed by trains, such as diesel or electricity, plays a significant role in their environmental impact. Diesel trains emit large amounts of carbon and other harmful pollutants, affecting the health of communities living near freight railroads. Additionally, the manufacturing process of trains and the energy mix of the country they operate in also factor into their overall carbon footprint.

Skytrains run on diesel, electricity, or both

Skytrains, like other trains, can run on diesel, electricity, or a combination of both. Electric trains are becoming more commonplace, but diesel trains are still in use, particularly in locations where electric trains are not viable. For example, diesel trains are used north of Edinburgh, where electric trains cannot run.

Diesel-electric trains use a diesel engine to generate the electricity that powers the electric motors, which in turn propel the locomotive. This combination of technologies offers several advantages. Firstly, it allows the diesel engine to run at a constant load, reducing the impact of challenging operating conditions. Secondly, the electric motors do not require mechanical transmission, clutches, or other parts that can fail or wear out prematurely. Thirdly, the engine only needs to power the electric motors, reducing the risk of breakdowns. Finally, the use of turbochargers in diesel-electric trains can increase power by up to 400% compared to a similar-sized naturally aspirated engine, allowing for smaller engines without sacrificing performance.

Diesel-electric trains are also a more economically viable option in certain situations. For example, where power lines are not available, generating power for electric motors using a diesel engine is more efficient than relying on batteries, which would add weight, reduce speed and cargo capacity, and increase downtime due to the need for frequent charging.

However, diesel trains produce more pollution than electric trains. Diesel fuel releases a greater amount of carbon than electricity from the grid, which is becoming increasingly decarbonized through the removal of fossil fuel power stations. For example, in the UK, where gas and wind power are the main sources of electricity, diesel trains produce an average of 41g CO2e per passenger km, while more energy-efficient trains, such as the Eurostar, produce only 6g CO2e per passenger km.

Therefore, while skytrains that run on diesel fuel may be necessary in certain situations, they contribute more to pollution than those powered by electricity.

Diesel releases the most carbon, while electricity has a lower carbon intensity

Skytrains, like any mode of transport, contribute to pollution. The type of energy that a train consumes, such as diesel or electricity, is a key factor in determining its carbon footprint.

Diesel releases the most carbon among fuel options, while electricity has a lower carbon intensity. Diesel trains produce an average of 41g of CO2e per passenger km, while more energy-efficient trains like the Eurostar, which uses electricity, produce only 6g of CO2e per passenger km. This difference is primarily due to the carbon content of the fuel, as diesel combustion releases a greater amount of carbon dioxide compared to electricity generation.

The UK's transition from diesel to electric trains, such as the introduction of modern electric and bi-mode Azuma trains, has resulted in a significant reduction in carbon-intensive diesel consumption. This shift aligns with the UK's decarbonization efforts, which involve replacing fossil fuel power stations with low and zero-carbon alternatives.

It is important to note that the carbon footprint of electric trains is influenced by the energy mix of the country. For example, France derives 66% of its energy from nuclear power and 28% from wind and hydropower, resulting in a greener energy mix than the UK. Consequently, an electric train in France may have a lower carbon footprint than one in the UK due to the cleaner electricity source.

Additionally, the lifespan of trains and the frequency of renewal play a role in their environmental impact. Trains are typically built to last several decades, which means transitioning to more energy-efficient models can take longer compared to cars, which are renewed more frequently.

Rail companies remanufacture old locomotives, allowing them to run for decades

Locomotives are expensive to replace and are not produced on a large scale, so rail companies often remanufacture old ones, allowing them to run for decades. Rail companies like Progress Rail have locomotive facilities equipped to handle specific locomotive overhaul and remanufacture requirements. They provide cost-effective solutions and have improved the reliability and extended the life of numerous locomotives.

Remanufacturing locomotives is a more sustainable option than building new ones, as it reduces the need for raw materials, refining, and transportation. It also allows for the integration of new technologies, making older locomotives more fuel-efficient and environmentally friendly. For example, LNER retired its old fleet of diesel high-speed trains and introduced modern electric and bi-mode Azuma trains, reducing carbon-intensive diesel consumption by 30% compared to 2019.

In some cases, older locomotives are used for tourism and passenger transport, while newer, more fuel-efficient machines handle freight and heavy loads. The Norfolk and Western 475, a steam locomotive from 1906, was restored and returned to service for passenger use. The Canadian National 7312, built in 1908 and refurbished in 1960, was also used for passenger and freight services for decades.

The energy mix of different countries also affects the carbon footprint of electric trains. For example, an electric train in France is likely to have a lower carbon footprint than one in the UK due to its higher proportion of nuclear and renewable energy sources. Rail companies can further reduce their environmental impact by transitioning to renewable energy sources for powering trains, as the Eurostar is currently doing.

The US freight rail system disproportionately affects communities of colour and low-income communities

Northeastern Illinois, a major freight hub, is home to a quarter of all rail freight in the U.S. However, this activity brings pollution, safety concerns, and traffic delays. Many of these issues disproportionately affect low-income communities and communities of colour. For example, communities of colour are underserved by unreliable and underfunded public transportation systems. They also suffer from the pollution of roads and highways that run through their neighbourhoods, increasing the risk of contracting diseases such as COVID-19.

In 2020, transportation policy contributed to the disproportionate impact of COVID-19 on Black communities. This was due to a lack of reliable transportation options and higher exposure to pollution from roads and highways. Additionally, the construction of highways has historically decimated Black communities, leading to white flight to the suburbs and contributing to intense racial segregation and concentrated poverty.

Furthermore, low-income communities of colour in urban areas across the U.S. experience an average of 28% more nitrogen dioxide (NO2) pollution than high-income, majority-white neighbourhoods. This disparity is driven by their proximity to trucking routes and major roadways where diesel trucks emit NO2 and other harmful pollutants. Cities with larger populations tend to have greater disparities in NO2 pollution, with Phoenix, Los Angeles, and Newark, NJ, exhibiting discrepancies in NO2 exposure of over 40%.

To address these issues, the U.S. Department of Transportation (DOT) has initiated the Rural Opportunities to Use Transportation for Economic Success (ROUTES) program. The program aims to improve rural transportation infrastructure and meet safety and economic competitiveness goals. Additionally, the Infrastructure Investment and Jobs Act (IIJA) provides federal funding for rail improvement projects, including rural communities, to enhance the nation's rail network and address deteriorating conditions and high fatality rates.

Electric trains in France are likely to have a lower carbon footprint than in the UK

While trains are generally becoming more environmentally friendly, the energy mix of the country they are operating in plays a significant role in determining their carbon footprint. In the UK, gas accounts for around 38.5% of the electricity supply, with 26.8% from wind power and 15.5% from nuclear power. In contrast, France derives 66% of its energy from nuclear sources, and 28% from wind and hydropower. This greener energy mix in France means that electric trains there are likely to have a lower carbon footprint than those in the UK.

The carbon footprint of travel by train or car depends on factors such as the type of energy consumed and the class of the train ticket. For example, some of the most energy-efficient trains, like the Eurostar, produce only 6g CO2e per passenger km, while diesel-powered trains can produce an average of 41g CO2e per passenger km. The Eurostar, which operates between the UK and France, is transitioning to renewables, and its trains emit up to 40 times less CO2 than flying when considering the overall footprint (traction energy and rail ecosystem).

The lifespan of trains and cars also affects their environmental impact. Cars tend to be replaced more frequently than trains, with car owners in the UK keeping their vehicles for an average of six years. This allows for quicker technological advancements and the adoption of more energy-efficient models. Trains, on the other hand, are built to last for several decades, resulting in a slower transition to more energy-efficient models. However, the shorter lifespan of cars can be advantageous as it enables the adoption of greener electric versions, while the longer lifespan of trains can result in higher overall emissions over time.

While electric trains in France may have a lower carbon footprint than those in the UK due to the country's energy mix, it's important to consider other factors as well. The specific model of the train, the distance travelled, and the infrastructure supporting the rail network can all impact the overall carbon footprint. Additionally, the carbon intensity of the electricity grid is constantly changing, with the UK's grid decarbonizing by removing fossil fuel power stations and adopting low-carbon alternatives. These factors collectively influence the carbon footprint of electric trains in France and the UK, making it a complex and dynamic issue.

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