Helena Joyce
Greenhouse gas emissions from transportation account for about 28% of total US greenhouse gas emissions, making it the largest contributor to US GHG emissions. Public transportation is a crucial component in the effort to reduce these emissions. While cars usually carry just one or two people at a time, a bus or train can carry many more, making public transportation far more efficient in terms of emissions per person. However, the debate around the environmental impact of public transportation is ongoing, with some arguing that the adoption of electric vehicles and improvements in fuel efficiency are also key factors in reducing emissions.
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What You'll Learn
Public transport reduces CO2 emissions by 45%
Greenhouse gas emissions from transportation account for about 28% of total US greenhouse gas emissions, making it the largest contributor to US GHG emissions. However, public transportation offers a way to significantly reduce these emissions.
Public transportation has been proven to reduce CO2 emissions by 45% compared to driving alone. This is because every vehicle on the road releases an average of one pound of CO2 per mile driven. By taking public transportation, individuals can save up to 20 pounds of CO2 emissions per day, or more than 48,000 pounds in a year, for a 20-mile solo commute by car. This is equivalent to a 10% reduction in all greenhouse gases produced by a typical two-adult, two-car household.
Additionally, public transportation use saves the US the equivalent of 4.2 billion gallons of gasoline annually and more than 11 million gallons of gasoline per day. This is equivalent to 300,000 fewer automobile fill-ups every day. The use of public transportation also reduces congestion, saving nearly $21 billion in congestion costs in 2011.
Other ways to reduce carbon emissions include using renewable fuels, car-sharing, and active transportation such as walking or biking for short trips, which can reduce travel emissions by up to 75%.
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Buses are less efficient when not full
Public transportation has a proven record of reducing congestion and vehicle emissions. It is estimated that public transportation in the US saves 37 million metric tons of carbon dioxide annually. However, the fuel efficiency of public transportation depends on various factors, including the occupancy level and population density of the region.
Buses, in particular, can be less efficient when not full. When buses operate below a certain occupancy level, they become less efficient than cars. This is because the fuel efficiency of mass transit increases with population density. In regions with low population density, such as the US, buses may have lower occupancy levels, resulting in decreased fuel efficiency.
For example, the energy cost of London's buses in 2006-07 was 32 kWh per 100 p-km, which is higher than the energy cost of a baseline car. During peak hours, when buses are more likely to be full, they become more fuel-efficient per average-passenger-mile than cars. However, during off-peak hours, if a bus is not full, it may be more energy-efficient for passengers to travel by car or taxi.
To improve the efficiency of bus transportation, it is crucial to maintain a certain occupancy level. Strategies such as optimizing routes and schedules, implementing demand-responsive transportation, and promoting public transportation through incentives can help increase bus occupancy and reduce the environmental impact of bus transportation.
Additionally, it is worth noting that other factors beyond energy efficiency, such as road infrastructure and traffic conditions, also play a role in the overall environmental impact of buses. The benefits of reduced congestion and the elimination of car trips associated with public transportation contribute to the overall environmental benefits of buses, even when they are not at full capacity.
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The US has the highest transport emissions
The transportation sector is a significant contributor to US greenhouse gas (GHG) emissions, accounting for about 28% of the total. This includes emissions from cars, trucks, airplanes, and railroads. While there have been efforts to improve fuel economy and reduce emissions, the absolute increase in the transportation sector has been more significant than in any other sector between 1990 and 2022.
Motor vehicles, including cars and trucks, are the primary source of transportation emissions, accounting for 83% of CO2 emissions in 2019. Personal vehicles and commercial trucks, the most common forms of passenger and freight transportation, produce more CO2 emissions per passenger-mile or ton-mile than other modes of transportation. However, improvements in fuel economy and efficiency have led to a slight decrease in emissions since 2005, despite increased travel.
To reduce emissions, the US Environmental Protection Agency (EPA) has implemented various strategies, including the SmartWay program, which improves supply chain efficiency and reduces greenhouse gases for participating companies. The EPA also sets GHG emissions and fuel economy standards for vehicles, encouraging the use of low-emission and electric vehicles. Additionally, the Renewable Fuel Standard program promotes the use of renewable fuels produced from plants and biomass, reducing reliance on imported oil and fossil fuels.
Public transportation plays a crucial role in reducing emissions and congestion. It is estimated that public transportation in the US saves 37 million metric tons of carbon dioxide annually, equivalent to the emissions from electricity generation for nearly 5 million households. A person switching from a 20-mile solo commute by car to public transportation can reduce their annual CO2 emissions by over 48,000 pounds. Public transportation also saves the US the equivalent of 4.2 billion gallons of gasoline annually and reduces congestion costs.
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Electric vehicles reduce harmful air pollution
Greenhouse gas emissions from transportation account for about 28% of total US greenhouse gas emissions, making it the largest contributor to US GHG emissions. Electric vehicles (EVs) are an essential part of a clean energy future.
A new report by the Electric Power Research Institute (EPRI) and the NRDC confirms that fueling transportation through electricity instead of petroleum can significantly reduce emissions of greenhouse gases and other air pollutants that threaten our health and the environment. The Environmental Assessment of a Full Electric Transportation Portfolio found that a PEV today has 54% lower lifetime carbon pollution, and in 2050, the reduction could be as much as 59 to 71%.
EVs have zero tailpipe emissions, which means they eliminate exhaust emissions of NOx and PM2.5, and they also reduce particulates from brake wear due to regenerative braking. Nitrogen oxides (NOx) and particulates (PM2.5) are particularly harmful to human health as they can get lodged into our respiratory systems. However, it's important to note that if EVs are heavier, they could increase tyre wear and road dust pollution.
The amount of carbon pollution generated by EVs depends on how local power is generated, for example, using coal or natural gas creates more carbon pollution than using renewable resources like wind or solar. Even accounting for these electricity emissions, research shows that an EV is typically responsible for lower levels of greenhouse gases than an average new gasoline car. As renewable energy sources become more prevalent, the total GHGs associated with EVs will continue to decrease.
Public transportation in the US saves 37 million metric tons of carbon dioxide annually, and even moderate increases in bicycle use each year could save an additional 6 to 14 million tons. Every vehicle on the road releases an average of one pound of CO2 per mile driven, so taking public transportation or switching to an EV can significantly reduce an individual's carbon footprint.
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The EPA is taking action to reduce GHG emissions
Greenhouse gas (GHG) emissions from transportation account for about 28% of total US greenhouse gas emissions, making transportation the largest contributor to US GHG emissions. Public transportation, on the other hand, saves the US the equivalent of 4.2 billion gallons of gasoline annually, or more than 11 million gallons of gasoline per day. A single person who switches from a 20-mile solo commute by car to existing public transportation can reduce their annual CO2 emissions by 20 pounds per day, or more than 48,000 pounds in a year.
- The EPA and DOT have issued a joint rule-making that sets GHG emissions and fuel economy standards for cars, light trucks, and heavy-duty trucks, the largest sources of greenhouse gases from transportation. Light-duty GHG regulations for passenger vehicles and trucks are projected to cut 7 billion metric tons of GHG emissions over the lifetimes of the vehicles sold in model years 2027-2032.
- In March 2024, the EPA announced a final rule, "Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles – Phase 3," which sets stronger standards to reduce GHG emissions from heavy-duty vehicles beginning in model year 2027.
- The EPA has finalized federal greenhouse gas emissions standards for passenger cars and light trucks for model years 2023 through 2026, leveraging advances in clean car technology to improve public health, reduce climate pollution, and save drivers money.
- The EPA's SmartWay program is a collaboration with the freight transportation industry that helps improve fuel efficiency and save money.
- The EPA's Renewable Fuel Standard program aims to reduce greenhouse gas emissions and expand the nation's renewable fuels sector by promoting the use of renewable fuels produced from plants, crops, and biomass.
- The EPA has developed international carbon dioxide emissions standards for aircraft in collaboration with the Federal Aviation Agency and the UN's International Civil Aviation Organization (ICAO).
- The EPA's Combined Heat and Power Partnership (CHP) Resource Center provides tools and resources to help evaluate CHP as a means to reduce the environmental impacts of power generation and improve operational efficiency.
- The EPA's AgSTAR program promotes the use of biogas recovery systems to reduce methane emissions from livestock waste.
- The EPA's Natural Gas STAR Methane Challenge Program recognizes oil and natural gas companies that commit to reducing methane emissions.
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Frequently asked questions
Public transportation in the US saves 37 million metric tons of carbon dioxide annually. This is equivalent to the emissions from the electricity generated for 4.9 million households.
Public transportation produces less pollution than private vehicles. Taking public transportation reduces CO2 emissions by 45% compared to driving alone. A single person switching from a 20-mile solo commute by car to public transportation can reduce their annual CO2 emissions by 48,000 pounds.
Using public transportation helps to reduce congestion and improve air quality. This can lead to improved public health, with fewer cases of respiratory ailments such as asthma and even cancer. Additionally, less driving contributes to reduced noise pollution.
In wealthy countries with a history of transit-oriented development, such as Japan, South Korea, Switzerland, and Germany, public transit use is high, and greenhouse gas emissions from transportation are relatively low. In the US, public transit use has declined since the 1960s due to a focus on highway development, and transportation emits more greenhouse gases than any other sector.
