How Can We Reduce Emissions From Urban Transportation?

Emissions of greenhouse gases (GHGs) and other pollutants are a pressing concern for environmental and human health. Despite recent declines in the U.S., the global level of emissions remains at historic levels, leading to alarm among public health advocates and climate change activists alike. [1]

Although there are many factors behind these historically high emissions levels, none is as significant as transportation. In the U.S., the transportation sector accounts for 29% of all GHG emissions, ahead of even electricity generation and industry. [2] These emissions are highly concentrated in urban areas. According to the United Nations, 60% of GHGs come from cities, where cars and other modes of transportation relying on Internal Combustion Engines (ICE) are especially prominent. [3]

This makes urban transportation a strategic target for reducing emissions and curbing their impact on the environment and public health. The good news is that more than 10,000 cities have already committed to reducing carbon emissions by 2050. [4] Still, if history is any indication, curbing transportation emissions is easier said than done. Ultimately, city planners, transportation agencies, and many other stakeholders must come together with a strategic plan.

What will it take to reduce emissions from transportation, and just how important is this task? In this article, we’ll explore:

• The cost of urban emissions
• Shifting the urban transportation paradigm
• Picturing the future with big data

The Cost of Urban Emission

Emissions are more than a nuisance — they exact a heavy toll on the global economy. In the U.S. alone, pollution accounts for around 5% of the nation’s gross domestic product in damages each year, or $1.3 trillion in 2023. More than mere dollars and cents, however, the costs of pollution are particularly prominent in terms of public and environmental health. [5]

Damaging Public Health

By any estimation, pollution is a serious public health concern. According to one in-depth study, fine particulate matter from numerous toxic pollutants contributes to between 100,000 and 200,000 deaths in the U.S. each year. The transportation sector is responsible for the second-largest number of these deaths, behind only industrial and commercial activity. [6]

No matter who is involved, such a large number of deaths is tragic. Yet, the tragedy is made worse by inequity, as pollution disproportionately impacts already vulnerable Americans. Children, pregnant people, older adults, people of color, and those living in poverty are among those most at risk for adverse outcomes from pollution. [7]

Accelerated Climate Change

GHG emissions are the single largest contributor to climate change since the mid-20th century. [8] Research has connected emissions from human activity to a host of environmental events, including temperature extremes, surges in precipitation, more frequent droughts and wildfires, and more devastating weather patterns.

The risk of these events continues to grow, and the Intergovernmental Panel on Climate Change (IPCC) warns of serious peril for major ecosystems if global temperatures aren’t brought under control. If global averages reach temperatures of at least 1.5 degrees Celsius above pre-industrial levels, the effect on human, plant, and animal life may be irreversible, even catastrophic. [9]

Shifting the Urban Transportation Paradigm

In light of such devastating consequences, reducing carbon emissions is becoming a top priority for many involved in public policy and planning. Urban transportation represents an important target for these changes, as small adjustments in this sector could have an outsized impact on reducing pollution.

Realizing these outcomes requires three critical shifts in how we approach transportation in urban areas.

Move People First, Not Cars

The first and most important step in reducing urban transportation emissions is to shift away from a car-centric approach to transportation planning. The purpose of any type of transportation is to move people from one place to another, but many of our cities focus on moving cars.

Instead of merely building more and wider roads designed only for vehicles, planners can focus on building complete streets — ones that make room for all kinds of commuters, including pedestrians, bikers, and users of public transit. Centering multimodal transportation will help incentivize and enable more commuters to use these alternative methods.

Reducing reliance on household vehicles could have a substantial effect on urban emissions. According to the United Nations, each person who switches from cars to public transport could reduce their carbon emissions by up to 2.2 tons per year. [10] Another study shows that while public transit cuts GHG emissions by 58% compared to cars, cycling lowers them by 98% — meaning both offer substantial emissions reduction potential. [11]

The more transportation planners can leverage detailed data to inform their plans for new or updated roads, the more effective these changes can be. For instance, planners in Oregon’s largest special park district, the Tualatin Hills Park & Recreation District, were able to use detailed origin-destination data to confirm the value and potential impact of installing a bike-pedestrian bridge to move more commuters over a busy highway — without adding more car traffic.

Emphasize Electric

Although it’s possible to reduce emissions and other urban transportation problems by shifting the focus away from vehicles, it’s not feasible to entirely eliminate the need for cars in our cities. Where they are still needed, then, it’s critical to accelerate the move toward electric vehicles (EVs) and away from gas-powered vehicles.

One recent study showed that adopting EVs would reduce carbon emissions significantly in every state. In states like Washington or Vermont, which already rely on clean electricity sources, EV usage could reduce pollution from carbon emissions by more than 90%. Even in states like Kentucky and West Virginia, where electricity generation relies heavily on fossil fuels, emissions would drop by over 30% with a full transition to EVs. [12]

With more federal support for the EV initiative than ever, now is an ideal time for cities to encourage drivers to increase fuel efficiency and electrify their driving. In addition to the National Electric Vehicle Infrastructure (NEVI) grant program introduced by the Bipartisan Infrastructure Law (BIL), massive federal tax credits are also available for EVs and chargers, and many cities and states are taking a step further by providing credits of their own or encouraging utility companies to create rebate programs and other incentives. Cities themselves can also leverage such programs to expand public charging installations and electrify public transit.

Rethink City Planning

As essential as investments in electrification and multimodal transportation are to reducing carbon emissions, they aren’t sufficient solutions to the problem. Urban planners must think bigger, considering land use, transportation, operations, policy, and more in a comprehensive approach to emissions-reducing city planning.

With a holistic view, city planners can make progress by focusing on initiatives such as investing in green buildings, expanding renewable energy production, and improving waste management. [13] They can also consider the best ways to invest in tomorrow’s transportation infrastructure.

This requires thoughtfulness and intentionality. The BIL provides historic levels of funding for cities to upgrade their transportation infrastructure, but studies show that these investments could actually lead to increased emissions if not used properly. For instance, the Georgetown Climate Center recommends that planners focus on a “fix it first approach” of maintaining existing roads and investing in public transit, EVs, and other low-carbon options — rather than building more roads or expanding existing ones, which could induce demand and bring more pollution. [14]

Again, choosing the right updates and planning initiatives requires access to extensive data, both in terms of transportation patterns and existing urban emissions levels. Only when properly informed can planners choose initiatives that will result in successful emissions reductions.

Picturing the Future With Big Data

At every turn in the fight against carbon emissions, data is critical for making informed, effective decisions. In transportation, planners must have access to a wide range of emissions-related metrics, such as:

• Vehicle Miles Traveled (VMT)
• Annual Average Daily Traffic (AADT)
• Vehicle Hours of Delay (VHD)
• Origin-Destination (O-D) and routing patterns
• Average trip speed and duration
• Electric vehicle usage
• Changes in walking and biking activity
• Truck traffic by vehicle class (light-, medium-, and heavy-duty)

As urbanization continues to transform U.S. cities, this data has never been more critical for the decision-making process. Big data providers like StreetLight are helping to fill data gaps that would otherwise prevent planners from understanding their city’s impact on the climate. That’s how the  Twin Cities Metropolitan Council was able to share critical emissions data with local governments, equipping them with crucial insights for local planning, rather than generic national numbers.

The Southern Maine Planning and Development Commission took a similar approach, using big data to power urban planning that reduces emissions. In the video below, see how they measured statewide VMT to develop regional mitigation strategies.

To learn more about how you can use data to cut emissions and improve your city’s climate impact, download our eBook, Measure & Mitigate: Transportation Climate Data Solutions.

1. Stanford. “Global carbon emissions from fossil fuels reached record high in 2023.” https://sustainability.stanford.edu/news/global-carbon-emissions-fossil-fuels-reached-record-high-2023
2. United States Environmental Protection Agency. “Fast Facts on Transportation Greenhouse Gas Emissions.” https://www.epa.gov/greenvehicles/fast-facts-transportation-greenhouse-gas-emissions
3. United Nations. “Generating power.” https://www.un.org/en/climatechange/climate-solutions/cities-pollution
4. United Nations. “Seven Ways Cities Can Take Climate Action.” https://unfccc.int/news/seven-ways-cities-can-take-climate-action#
5. Standford. “How much does air pollution cost the U.S.?” https://sustainability.stanford.edu/news/how-much-does-air-pollution-cost-us
6. Environmental Science and Technology Letters. “Reducing Mortality from Air Pollution in the United States by Targeting Specific Emission Sources.”  https://pubs.acs.org/doi/10.1021/acs.estlett.0c00424
7. American Lung Association. “Who is Most Affected by Outdoor Air Pollution?” https://www.lung.org/clean-air/outdoors/who-is-at-risk
8. United States Environmental Protection Agency. “Climate Change Indicators: Greenhouse Gases.” https://www.epa.gov/climate-indicators/greenhouse-gases
9. Intergovernmental Panel on Climate Change. “Climate Change 2022: Impacts, Adaptation and Vulnerability.” https://www.ipcc.ch/report/ar6/wg2/
10. United Nations. “Your guide to climate action: Transport.” https://www.un.org/en/actnow/transport
11. ScienceDirect. “The climate change mitigation effects of daily active travel in cities.” https://www.sciencedirect.com/science/article/pii/S1361920921000687
12. Yale Climate Connections. “Electric vehicles reduce carbon pollution in all U.S. states.” https://yaleclimateconnections.org/2023/09/electric-vehicles-reduce-carbon-pollution-in-all-u-s-states/
13. National League of Cities. “The Top 5 Ways Cities Are Addressing Climate Change.” https://www.nlc.org/article/2022/04/22/the-top-5-ways-cities-are-addressing-climate-change/
14. Georgetown Climate Center. “Issue Brief: Estimating the Greenhouse Gas Impact of Federal Infrastructure Investments in the IIJA.” https://www.georgetownclimate.org/articles/federal-infrastructure-investment-analysis.html