Advanced Search
The transportation sector plays an integral role in day-to-day life across the United States. Roads, railroads, airways, and shipping routes make it possible for people, goods, and services to traverse communities, the country, and the globe. At the same time, the transportation sector is responsible for about 29% of U.S. greenhouse gas emissions, with more than 94% of vehicle fuel coming from petroleum. Light-, medium-, and heavy-duty cars and trucks are responsible for more than half of all transportation emissions.
There are significant opportunities to reduce carbon emissions and pollution from transportation by switching to more low- or no-emissions transportation modes like transit and biking, electrification, and increasing efficiency through changes in design and operation. In addition to addressing climate change, these efforts also improve public health, increase economic activity, and reduce noise pollution. There are also efforts to increase the resilience of transportation infrastructure to the impacts of climate change. From coastal rail lines experiencing severe erosion due to sea level rise and stronger storms to airports reducing the use of runways during extreme heat events, every part of the transportation sector needs to adapt to climate change in order to keep systems safe and running.
Every five years, Congress sets out to reauthorize surface transportation legislation, which has historically had an outsized focus on funding highway infrastructure but, in more recent iterations, has also funded public transit and rail. State departments of transportation play an essential role in implementing projects funded through these laws. Congress addresses aviation primarily through the Federal Aviation Administration reauthorization, which is also supposed to take place every five years.
Clickable Table of Contents:
Read More: Electrification | Hydrogen and Fuel Cells
Cars and trucks dominate the U.S. transportation scene. Roads, highways, and interstates weave a complex network across the country. While these roads connect many parts of the United States, they have also bisected communities, cutting people off from easy access to essential needs and making it hard to get around without personal vehicles. Roads also slice up habitats, making it harder for wildlife, especially migratory species, to thrive.
In 2023, the Federal Highway Administration reported 285 million registered vehicles and 238 million licensed drivers out of a total U.S. population of 335 million that year. Approximately 78% of people commute via car, van, or truck, and 69% of people drive alone. Cars and trucks are responsible for more greenhouse gas emissions than any other segment of the transportation sector, with trucks, SUVs, and minivans leading the way at 37% of total transportation emissions, large commercial trucks at 23%, and compact cars at 20% in 2022. While reducing driving miles—in favor of active mobility, public transit, and rail—is one way to reduce emissions from these vehicles, electrification is another solution being implemented at scale.
Carmakers sold 1.55 million electric vehicles (EVs) in 2024, representing about 10% of total new vehicles sold in the United States that year. More automakers are entering the EV market with each passing year, according to data from BloombergNEF and the Business Council for Sustainable Energy. EVs are an appealing option for drivers as they are quiet, provide a smooth drive, and are half as expensive to run as an internal combustion engine car. Heavy-duty vehicles are also being electrified. EVs require a robust charging network, which the United States is still in the process of building out. While EVs have many benefits, their batteries are made up of critical minerals, which, depending on their sources, can present supply chain issues, human rights concerns, and degradation of the environment where minerals are mined. International efforts are underway to establish clear standards for responsible critical mineral extraction, processing, and refining. Researchers are also exploring recycling and secondary recovery from mining waste, industrial byproducts, and other sources in order to reduce the demand for virgin critical minerals.
There are more than 5,000 public-use airports across the United States, supporting a commercial aviation network that served over 800 million passengers in 2023. The Federal Aviation Administration reports that at peak operational times, up to 5,500 aircraft can be in flight. This system plays a central role in national and global mobility, connecting cities, promoting economic activity, and moving people and goods across long distances. Approximately 5.87 million tons of goods worth $591 billion are transported annually in the air.
Aviation currently accounts for about 2.5% of global carbon dioxide emissions. However, because of the nature of high-altitude emissions, aviation has actually caused about 4% of global warming to date. With air passenger traffic predicted to increase by approximately 60% (from 811 million in 2019 to 1.3 billion in 2040), emissions from the aviation sector are poised to increase. Emissions are also expected to rise due to outdated air traffic systems that cause inefficient routing, extended taxiing, and delays. Modernizing these systems while addressing the air traffic controller shortage will become increasingly important in reducing unnecessary fuel use and emissions.
Sustainable aviation fuels (SAF), made from renewable feedstock such as woody biomass and soy or corn oil, present another opportunity to reduce emissions. Flights using SAF have reduced emissions from flying by 70 to 90%. While four major U.S. airports—Los Angeles International Airport and San Francisco International Airport in California, and Aspen/Pitkin County Airport and Telluride Regional Airport in Colorado—have SAF fueling options on site, most commercial aircraft still rely entirely on fossil fuels, with SAF making up less than 0.1% of the current fuel supply in the United States. To help close the gap, the U.S. Department of Agriculture, Department of Energy, and Department of Transportation launched the Sustainable Aviation Fuel Grand Challenge to reduce lifecycle emissions by 50% and ramp up production of SAF to 35 billion gallons by 2050—which would meet all domestic airline energy demand.
Active mobility describes human-powered movement, such as walking and cycling, while micromobility includes the use of electric-assist options like electric bicycles (e-bikes) and e-scooters. Both active mobility and micromobility provide a host of benefits for individuals, communities, and the climate. People get exercise, spend time outside, and can communicate and interact with their environment; businesses have more visibility; and all these forms of transportation use minimal or no direct fossil fuel energy. Communities and decision-makers can encourage active mobility by investing in infrastructure that makes these forms of transportation safe, accessible, and enjoyable. For example, dedicated bike lanes, shade trees, rain gardens along streets, and well-maintained sidewalks all make active mobility and micromobility more accessible.
In 2023, just under 3% of the U.S. population walked or biked to work, and about 13% of students reported walking to and from school. While people walk, bike, and scooter to commute, get to appointments, do errands, and recreate in all corners of the United States, active mobility is particularly popular in cities. According to C40 Cities, a coalition of climate-conscious mayors, about 35% of trips people take in most cities around the world are under two miles, and approximately 50% of trips are under seven miles—making walking, cycling, or scootering a viable option, if the infrastructure supports it. Similarly, the National Association of City Transportation Officials estimates that in 2024, people took 133 million trips in the United States using bike and scooter share programs, with trips averaging 15 minutes and 1.5 miles. In 2023, such bike and scooter shares prevented 81 million pounds of carbon dioxide emissions by replacing car trips. Models by the Department of Energy’s National Renewable Energy Laboratory suggest that peak adoption of active mobility and micromobility share programs could see the United States use 2.3 billion fewer gallons of gas each year.
There are about 6,800 public transit providers in the United States operating subways, trams, buses, and ferries. These operators span rural and urban areas and move millions of people every day. As of 2023, about 3.5% of people relied on public transportation for their commute. School buses play a significant role in transporting students, with 26 million children taking the bus to school every day.
While many of these public transportation systems still rely on fossil fuel energy—for example, 90% of school buses are diesel-powered—they still have much lower per-capita emissions than cars. Electrifying public transportation is a promising option to further reduce greenhouse gas emissions while improving local air quality, decreasing noise pollution, enabling smarter land-use decisions, and supporting jobs. Researchers found that electrifying bus fleets across the United States could reduce emissions from those buses by 33-65% by 2038, depending on the speed of adoption and overall grid decarbonization, and could help reduce asthma rates.
Maintaining and improving public transportation systems is only possible with investment, and the United States is falling behind. As of 2025, there was a $140.2 billion backlog in public transportation infrastructure upgrades and repairs needed across the country according to the Federal Transit Administration. Finding ways to scale up investment in electrification as well as in overall facility and infrastructure maintenance, accessibility, and resilience to climate impacts is essential to ensure public transit remains an option for as many people as possible and to continue to drive down emissions across the transportation sector.
Railways move 28% of U.S. freight and tens of thousands of people across the country every day. The United States boasts 140,000 miles of freight rail lines underpinning an $80 billion industry that employs roughly 167,000 people. Rail is a more energy-efficient way to move cargo than heavy-duty trucks, but diesel-powered freight rail actually produces about twice as much air pollution (namely, particulate matter and nitrogen oxides) by unit of fuel burned.
On the passenger rail side, Amtrak, the sole national passenger railroad company, connects people across rural and urban America, and reported record ridership in fiscal year 2024 with 32.8 million passengers. Most trains in the United States—both freight and passenger—are currently diesel-powered; however, Amtrak does operate 108 electric locomotives along the Northeast corridor. Researchers have found that Amtrak’s diesel trains use three times as much energy per passenger-mile as its electric ones.
While passenger rail plays an important role in a decarbonized transportation system, widespread access to rail has diminished over the past 50 years. The increased use of cars and air travel, along with private and public disinvestment, have led to a bare-bones passenger rail network across most of the United States. Created by Congress, Amtrak requires federal support to maintain and rebuild its network. In 2021, the Infrastructure Investment and Jobs Act (P.L. 117-58) invested $58 billion in passenger rail over five years. In 2025, Amtrak opened a new line from Mobile, Alabama, to New Orleans, Louisiana, representing a significant step in the project of extending passenger rail’s reach.
Freight and passenger rail share most of the country’s rail lines, which are owned by the freight companies. According to the American Society of Civil Engineers, the largest freight railroad companies invest an average of 18% of their revenue in infrastructure repairs and improvements, with smaller, short-line railroad companies in the 25% range. These freight companies move everything from grain, lumber, and paper to chemicals, petroleum, and cars.
Tools like the Zero Emission Rail Project Dashboard demonstrate how both freight and passenger rail companies in the United States and abroad are using different methods—such as battery electric combined with hydrogen fuel cells and hydrogen combined with overhead catenary electric systems—to reduce their greenhouse gas emissions.
According to the American Society of Civil Engineers, in the United States, 41.5% of international trade by value goes through ports. All ports need to pay particular attention to climate impacts and consider climate adaptation steps. Ports on the ocean are inherently vulnerable to sea level rise and storm surge, while riverine ports need to consider climate resilience measures to deal with flooding as well as low water levels (counterintuitively, climate change makes both more likely).
Container ships, which move almost 90% of global cargo, emitted 240.6 million tons of carbon in 2024. This represents the highest level of carbon dioxide emissions recorded by the industry—the result of ships being diverted from the most efficient routes because of geopolitical conflicts. In 2025, the International Maritime Organization agreed to a plan that aims to reach net-zero emissions from international shipping as close to 2050 as possible. At its core, the plan will set fuel standards that cap ship emissions. Companies whose ships exceed the emissions threshold will be fined. This effort should encourage companies to innovate and decarbonize, including by making everything more efficient—from the ships themselves to the shipping routes and overall supply chains. Countries, including the United States, have delayed implementation of this plan until at least 2026.
There are numerous pathways to decarbonize the transportation sector while also achieving economic gains, improved public health outcomes, and increased resilience in the face of climate impacts. The U.S. Environmental Protection Agency emphasizes fuel switching, increasing efficiency, reducing travel time, and considering different modes of transportation. In 2025, the U.S. Department of Transportation published a comprehensive report, Climate Strategies that Work, based on the U.S. National Blueprint for Transportation Decarbonization. While federal engagement on these strategies would scale up and accelerate the transition to a decarbonized sector, the private sector and subnational governments can also implement these solutions. Some of the recommended strategies are:
Last updated in October 2025.
View more entries tagged as Transportation
Advancing science-based climate solutions
Top-Rated Climate Nonprofit – 4-Star Charity