Despite recent adoption of more stringent vehicle emission regulations in several major vehicle markets, the transportation sector remains a major contributor to air pollution and greenhouse gas emissions. Decarbonization of the transport sector can create a cleaner, healthier, and more affordable future while protecting the transportation efficiency and interconnectedness we’ve come to expect. If we don’t change the way we transport goods and humans, however, we will confront obstacles to reduce emissions in line with the Paris Agreement and other global goals.
Transportation is the largest single contributor of US greenhouse gas emissions. In 2016, the transport sector surpassed the electric power industry as the single greatest US emitter of greenhouse gasses for the first time and then, in 2018, accounted for about 28.2% of total US greenhouse gas emissions. Ground transportation alone represents 18% of global CO2 emissions in recent years.
What Are Transportation Emissions?
There is growing concern that the Earth’s atmospheric composition is being altered by human activities, which is generally referred to as anthropomorphic climate change. Air pollution from transportation — especially carbon dioxide emissions — are of great concern and are central to several international treaties, such as the Paris climate accord. Moreover, non-CO2 pollutants emitted during transportation have many negative effects on air quality, climate, and public health.
Modern transportation relies heavily on petroleum. Burning one gallon of gasoline creates about 20 pounds of CO2, which means the average vehicle creates roughly 6 to 9 tons of CO2 each year.
The majority of greenhouse gas emissions from road, rail, air, and marine transportation are carbon dioxide (CO2) emissions resulting from the combustion of petroleum-based products, like gasoline, in internal combustion engines.
- In many US cities and towns, the personal automobile is the single greatest polluter. Road travel accounts for 3/4 of transport emissions. Most of this comes from passenger vehicles – cars and buses – which contribute 45.1%, according to the International Energy Agency.
- The other 29.4% comes from trucks carrying freight.
- While aviation is often the target of climate action accusations, it accounts for only 11.6% of transport emissions and emits just under one billion tons of CO2 each year – around 2.5% of total global emissions.
- International shipping contributes 10.6%.
- Rail travel and freight emits very little – only 1% of transport emissions.
- Other transport – which is mainly the movement of materials such as water, oil, and gas via pipelines – is responsible for 2.2%.
The global public transport market is anticipated to to record a steady growth of 8.11% compound annual growth rate due to the population growth.
How Transportation Emissions Affect Public Health
The transportation sector includes the movement of people and goods by cars, trucks, trains, ships, airplanes, and other vehicles. Emissions have increased in international aviation, domestic aviation, and international and coastal shipping. On-road diesel vehicles contribute the most to pollution and associated disease burdens.
A white paper from the Climate & Clean Air Coalition points to the global transportation sector as a major source of health burdens through its contribution to elevated fine particulate matter, ozone, and nitrogen dioxide concentrations.
Transportation activities produce tailpipe emissions, evaporative emissions, resuspension of road dust, and particles from brake and tire wear. Other important health impacts of the sector include noise, physical activity effects, and road injuries.
Transportation emissions globally are driven by many factors, including economic development, which often increases personal vehicle ownership and freight activity; changes in fuel quality; and introduction of emission controls on vehicles and engines to comply with tightening environmental standards. For these reasons, transportation emissions have been changing rapidly around the world.
Change is on the Roads & Rails & Waterways & in the Air
Global transport emissions increased by less than 0.5% in 2019 (compared with 1.9% annually since 2000), owing to efficiency improvements, electrification, and greater use of biofuels, according to the IEA. They say existing measures to increase efficiency and reduce energy demand must be deepened and extended for compliance with the Sustainable Development Scenario (SDS). The SDS holds the temperature rise to below 1.8 °C with a 66% probability without reliance on global net-negative CO2 emissions; this is equivalent to limiting the temperature rise to 1.65 °C with a 50% probability. Global CO2 emissions from the energy sector and industrial processes fall from 35.8 billion tons in 2019 to less than 10 billion tons by 2050 and are on track to net zero emissions by 2070.
Nature reports that decreases in mobility-related ground transportation emissions seemed to be more persistent in 2020, due to some warmer winter temperatures and reduced covid-19-related transport of goods and domestic and international aviation decreases:
- 13.0% lower in July of 2020 than in 2019
- monthly decreases in April and May were −38.6% and −32.6% respectively
- smaller in June at −15.2%
The report also relates that, although numerous organizations and some policy-makers are turning to a “Green Recovery” to revive economies and advance climate goals, the likelihood is that emissions will rebound and exceed pre-pandemic levels if recovery and stimulus efforts rely on carbon-intensive energy availability.
That means real-time transportation carbon monitoring as an integral element of policy making is necessary, the authors add, as ambitious climate goals, such as limiting the increase in mean global temperatures to 1.5 °C, “leave no time for such a Carbon Rebound.”
The Leap to Sustainable Transportation
Transitioning to zero-emission transport will become essential if we are to see a breathable, survivable world for our grandchildren and their children. Energy intensity must drop by 3.2% on average annually from 2020 to 2030 – more than double the annual average rate of decrease since 2000 – to put transport efficiency on track with the SDS.
Certainly, to reduce greenhouse gas emissions, individuals can use cleaner modes of transportation to get around, from public transit to biking and walking. But focusing only on individuals’ carbon footprints redirects responsibility from the world’s biggest transportation polluters. Long-term and lasting emissions decreases are needed in this century and must be based on structural and transformational changes in energy production systems and decarbonization of transportation.
As such, these changes require improvement of the carbon intensity of economies rather than decreases of human activities.
Electrification: It is clear that electric vehicles are far, far cleaner and greener than gasoline and diesel vehicles. Railways emissions, due to significant powering by electricity, have declined over the last several years. So there’s a lesson here. In July, 2020, 15 US States and DC joined forces on a joint memorandum of understanding to work collaboratively to advance and accelerate the market for electric medium- and heavy-duty vehicles, including large pickup trucks and vans, delivery trucks, box trucks, school and transit buses, and long-haul delivery trucks (big-rigs). The goal is to ensure that 100% of all new medium- and heavy-duty vehicle sales be zero emission vehicles by 2050 with an interim target of 30% zero emission vehicle sales by 2030.
Fuel Economy Standards: The Trump administration pushed ahead with its plan to gut the auto emissions standards put in place during the Obama administration. Other states can’t set their own standards, but they can opt to follow California’s motor vehicle emission regulations. The tailpipe standards that the Obama EPA put in place were designed to limit GHG emissions from cars by improving average fuel efficiency. These standards were developed jointly by the EPA, the US Department of Transportation, and California, which have overlapping legal authority to regulate cars. The Union of Concerned Scientists says that investing in technologies that increase the fuel economy of the US vehicle fleet will create domestic jobs, save consumers money at the pump, cut global warming pollution, and put us on a path to cut projected US oil consumption in half over the next 20 years.
Public Transportation: By eliminating one car and taking public transportation instead of driving, a saving of 30% of carbon dioxide emissions can be realized. But the US has a weak public transportation system. Have you ever been to Sydney, Australia? If you take a ferry across the harbor, there’s always a bus waiting for passengers who disembark. I live in populous southeast Florida, and there isn’t even a viable public transportation option to the major West Palm Beach airport. Even if we look at the existing data from the US Department of Transportation, 40% of America’s buses and 23% of its rail systems are deemed to be in marginal or poor condition; the estimated $98 billion that’s needed for repairs and maintenance has been backlogged for years. And that isn’t taking into account the need for new and innovative public transportation needs… Will the Moving Forward Act solve some of these problems? We’ll see.
New Ways of Thinking about Mobility: The City Fix outlines how promoting the use of shared cars and bicycles while also integrating advances in electric, autonomous and data-driven technologies can help move us to lower transportation emissions. If cities embrace automation, electrification, and ride sharing, research indicates an 80% transportation emissions cut In consideration of equity, accessibility and sustainability, new mobility can have a greater effect on both behavioral change and policy regulation.
We have it within our reach to reduce transportation emissions. To do so, we need to forge a sustained effort that will endure over many decades to come. Along with R&D and voluntary reductions, mandatory policies must be enacted to increase fuel economy and introduce technological innovations. Looking to significant changes like the Tesla Cybertruck and the Tesla Semi will not only offer structural reductions in emissions, they’ll bring in new cultural ways of thinking about transportation. As they say, if you build it, they will come.