Cars and other road vehicles produce about 15% of total global greenhouse gas emissions, making them one of the largest single sources of air pollution worldwide. In the United States specifically, passenger cars and light-duty trucks together account for 57% of all transportation emissions, which is the country’s largest emitting sector. But greenhouse gases are only part of the picture. Cars also release pollutants that directly harm human health, particularly in cities and near busy highways.
The Global Numbers
In 2019, the entire transportation sector (cars, trucks, planes, ships, and trains combined) produced 8.7 billion metric tons of CO2-equivalent emissions, up from 5.0 billion in 1990. That represents roughly 23% of all energy-related CO2 emissions worldwide. Road transport alone, meaning cars, trucks, buses, and motorcycles, accounts for 69% of those transportation emissions.
Passenger vehicles are the dominant force within road transport. Cars, motorcycles, and minibuses generate about 75% of all passenger-transport CO2 emissions. Buses and railways, despite carrying a fifth of the world’s passengers, produce only about 7%. The math is simple: most people drive alone or in small groups, burning fuel to move a two-ton vehicle a few miles at a time.
What U.S. Cars Emit
The EPA breaks down U.S. transportation emissions by vehicle type, and the 2022 data is revealing. Light-duty trucks (SUVs, pickups, and minivans) are the single largest category at 37%. Passenger cars contribute 20%. Medium- and heavy-duty trucks add another 23%. Commercial aircraft account for 7%, ships and boats for 3%, and rail for just 2%.
The shift toward SUVs and trucks has reshaped the emissions profile. Vehicle miles traveled by light-duty motor vehicles increased 47% between 1990 and 2022, and a growing share of those miles are driven in heavier, less efficient vehicles. A typical passenger vehicle emits about 400 grams of CO2 per mile. That adds up to roughly 4.6 metric tons of CO2 per year for a car driven the national average of about 11,500 miles.
Beyond Carbon Dioxide
CO2 gets the most attention because of climate change, but cars produce several other pollutants that matter for day-to-day air quality and human health. In the U.S., the transportation sector is responsible for approximately 45% of all nitrogen oxide emissions. Nitrogen oxides are the chemicals that help form smog and ground-level ozone, the haze that hangs over cities on hot summer days. In typical urban areas, cars, buses, trucks, and off-highway vehicles like construction equipment produce at least half of the hydrocarbons and nitrogen oxides that create that ozone.
Cars contribute less than 10% of direct particulate matter emissions (the tiny soot particles known as PM2.5 and PM10) according to EPA inventory data. That number is somewhat misleading, though, because it only counts particles that come directly out of tailpipes. A substantial amount of particulate matter forms in the atmosphere when gaseous emissions from vehicles react with sunlight and other chemicals. Brake dust, tire wear, and road surface abrasion add even more particles that don’t show up in tailpipe measurements.
How Far Car Pollution Travels
If you live or work near a busy road, your exposure to these pollutants is significantly higher than someone a few blocks away. EPA research shows that heavily traveled roadways influence air quality within about 500 to 600 feet downwind. Beyond that distance, pollution concentrations generally drop back to background levels.
That 500-to-600-foot zone is a meaningful health concern. Millions of people live, work, or attend school within that range of a major highway or high-traffic corridor. The pollutants most concentrated near roads, including nitrogen dioxide, ultrafine particles, and carbon monoxide, have been linked to higher rates of asthma, cardiovascular disease, and impaired lung development in children. The closer you are to the roadway, the higher the concentration.
Decades of Cleanup, and What’s Left
Individual cars are far cleaner than they used to be. The first major Clean Air Act in the U.S. required a 90% reduction in emissions from new automobiles. Catalytic converters, fuel injection, and progressively tighter standards have cut tailpipe pollutants like carbon monoxide, hydrocarbons, and nitrogen oxides dramatically per vehicle since the 1970s.
The problem is volume. Even though each car pollutes less, the total number of cars and the miles they travel have grown enormously. That’s why transportation emissions kept climbing from 5.0 billion metric tons globally in 1990 to 8.7 billion in 2019, despite cleaner engines. Per-vehicle improvements have been largely offset by more vehicles driving more miles.
How Electric Vehicles Compare
Electric vehicles eliminate tailpipe emissions entirely, but they still have a carbon footprint from manufacturing (especially the battery) and from the electricity used to charge them. Even accounting for all of that, the difference is large. A 2025 analysis by the International Council on Clean Transportation found that battery electric vehicles in the European Union produce 73% lower lifecycle greenhouse gas emissions than gasoline cars, factoring in manufacturing, fuel production, and driving over the vehicle’s full life.
The numbers break down to about 63 grams of CO2-equivalent per kilometer for an electric car versus 235 grams for a gasoline car. When charged exclusively with renewable electricity, electric vehicles drop to 52 grams per kilometer, a 78% reduction. The local air quality benefits are even more straightforward: no tailpipe means no nitrogen oxides, no carbon monoxide, and no exhaust particulate matter in the neighborhoods where people drive and live. Brake dust and tire wear still occur, but regenerative braking in electric vehicles reduces brake particle emissions significantly compared to conventional cars.