Our transportation system’s impact on the environment isn’t caused by tailpipe emissions alone. Protecting the natural resources we depend on requires rethinking how we travel.
The transportation sector is the largest source of greenhouse gas emissions in the United States, accounting for 28 percent of all emissions in 2022, according to the EPA. The number of vehicles on our roads, what they’re made of, and the amount we use them have direct impacts on our environment, from the nearby air all the way to the oceans.
Though electric vehicles may make a dent in the carbon emissions of vehicle tailpipes, there are a lot of other environmental impacts from the use of cars and the infrastructure we build for them. Research in this field is constantly evolving, so this is a snapshot of a few sources of pollution from our roadways, the impacts that pollution has, and what we can do about it.
At a glance
Pollution from roads impacts our surrounding water, air, and land. Vehicles and heavy-duty equipment on the roadway contribute to air pollution. When it rains, pollution on pavement (like oil from our vehicles) can be picked up and washed into the storm sewer, where it will be released to a nearby river or creek. Both air and water pollution can be left in soil and, in some cases, contaminate the groundwater.
There is a lot we need to do to reconsider the design of our communities to have a lighter impact on the world we live in. Rethinking our approach to land use and transportation can help reduce the amount of pavement we use overall and provide people with more travel options, which in turn helps reduce pollution.
Tires: How we use the road
There has been a lot of recent reporting on the ongoing research and recent regulations on toxic chemicals released by vehicle tires. These chemicals and plastics are harmful to fish and other aquatic life, disrupting these ecosystems and the lives of people who depend on them.
In 2020, scientists discovered that salmon in the Pacific Northwest were dying due to chemicals from car tires polluting the water. Tribes in this area, including the Yurok, the Port Gamble S’Klallam, and the Puyallup tribes, have historically depended on salmon for their food and culture, and these contaminants are a direct threat to their practices and their health. Other research has found a wide range of environmental impacts and emissions from car tires, from carbon dioxide to microplastics. In fact, it’s estimated that three quarters of the ocean’s microplastic pollution is from car tires. There are potential solutions: rain gardens are a promising way to filter these pollutants and alternatives to toxic chemicals are in development.
Salt: How we maintain the road
Road salt is an effective way to reduce the amount of ice on roads, parking lots, and other paved surfaces, and it’s a material commonly used by states, cities, and individuals for safer conditions in the winter. However, not all of the salt stays where it was applied, and overuse of road salt has led to high salt levels in downstream freshwater ecosystems and drinking water supplies. Research has found harmful impacts of deicing salts on salinity levels in lakes, streams, and wetlands, and negative health impacts of salt in drinking water supply.
Outside of the winter months, salt is stored in large piles, often in facilities located in low-income communities of color, such as Chelsea, Massachusetts, and releases dust and other toxins that worsen the surrounding air quality. Though salt may be one of the best materials available for safer paved surfaces in winter conditions, carefully managing how we use and store it can have lasting impacts on our health and nearby ecosystems.
Asphalt: What the road is made of
The pavement itself is its own source of pollution. Recent research has found that asphalt, a material used in pavement, releases compounds known to trigger asthma into the air, with more emissions on hotter, sunnier days. Low-income communities and communities of color already bear the brunt of poor air quality and extreme heat, which these pavement emissions can only exacerbate.
There are also water quality impacts from the roads: the materials used in repair, such as tar pitch in pavement sealers, have been shown to release pollution into stormwater that harms nearby aquatic ecosystems. Though the amounts of these pollutants released by the roads are not nearly on the scale of those from vehicle emissions, it’s important to understand that the roads themselves impact local environmental quality to begin to factor them into pollution and emissions measurements.
What can we do?
The sources of pollution described here—tires, salt, and asphalt—only scratch the surface of all the ways transportation infrastructure affects habitats, species, cultures, and public health. Some work is already being done to mitigate these specific impacts: California’s priority listing of 6PPD aims to protect salmon and other species at risk from car tires. Wisconsin’s Salt Wise initiative encourages municipalities to use brine, a more efficient form of road salt, and educates individuals and maintenance professionals on best practices at work and at home.
From a big-picture perspective, we can imagine a transportation system with a much lighter impact on the environment through less car dependence. Building instead for people to bike, walk, or use public transit reduces the number of cars on the road, and the number of tires contributing to species loss. This mode shift can be encouraged by Complete Streets, a strategy of making sure our transportation system works for everyone. When these redesigned streets lead to narrower lanes, to reduce speeds and make room for safe biking and walking, less salt is needed to cover less width of the road. And as we are able to shift away from car dependence, it is an opportunity to rethink how much pavement we have built—how much of this country is covered by roads and parking lots—and to reimagine how we could use that space in a way that improves our natural environment.
This section of the Saw Mill River in Yonkers was once covered by a parking lot. Efforts to daylight the river have helped restore wildlife habitat and bring natural beauty to a public space. (City of Yonkers)