Fifth National Climate Assessment
13. Transportation

The transportation sector is the largest source of GHG emissions in the United States, accounting for 28.5% of total national emissions in 2021 (Figure 13.1). Carbon dioxide (CO₂) remains the dominant GHG in the sector.¹ Limiting global warming to 1.5°C (2.7°F) above preindustrial levels would require a path toward achieving net-zero GHG emissions by 2050.² Yet under current policy as of November 2021, projections of US transportation sector energy use and GHG emissions in 2050 are similar to current levels.³ These projections assume continued increases in freight demand and in the number of miles traveled by vehicle per person, as well as existing powertrain trends. Other studies anticipate a more rapid switch to lower-GHG-emitting technologies resulting from declining costs of electric powertrains and other technologies, in part resulting from federal and state policy changes.^4,5,6,7

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Transportation remains the largest source of emissions in the US, with cars and light-duty trucks as the largest contributors.

Figure 13.1. Greenhouse gas (GHG) emissions from the US domestic transportation sector rose by about 19% between 1990 and 2021 and remain the largest source of total national GHG emissions, with passenger cars and all types of trucks being the most significant contributors to the rise in transportation emissions. “Other” refers to buses, motorcycles, pipelines, and lubricants. Numbers do not add up to 100% due to rounding. Figure credit: Arizona State University and Texas Tech University. See figure metadata for additional contributors.

Multimodal planning is done at the Metropolitan Planning Organizations (MPO) and/or state level and guided by input from many stakeholders. It involves a comprehensive assessment of transportation needs and includes public involvement to address the needs of multiple users. This includes encouraging increased mass transit use and active modes of transportation such as walking or biking.^8,9,10,11,12 Roadmaps to meet 2050 net-zero emissions targets often include extensive efforts to replace passenger, transit, and freight vehicles with electric vehicles (EVs), which will raise electricity demand (Chs. 5, 32). Some state governments and nonprofits are encouraging the use of low-carbon fuels like hydrogen and biofuels for heavy-duty and hard-to-electrify vehicles, as well as for waterborne transportation modes and aircraft (Ch. 32). Although increasing efforts to electrify vehicles could reduce fossil fuel emissions, consideration must also be given to the challenges posed by this change, such as increased strain on energy grids; transitioning electricity generation from fossil fuels to renewable resources for the purpose of charging EVs; and repurposing, recycling, and safe disposal of EV batteries (KM 13.4; Ch. 17).

The COVID-19 pandemic briefly reduced GHG emissions from the transportation sector, but emissions have mainly rebounded to pre-pandemic levels (KM 13.3; Focus on Compound Events; Focus on COVID-19 and Climate Change).^13,14,15,16 Passenger cars currently contribute the most to transportation emissions; however, the share of emissions from heavy trucks and non-road sources (e.g., trains, airplanes, and ships) is expected to grow due to increasing demand (Ch. 10). Heavy trucks and non-road vehicles use fuels that are more polluting or could cause greater GHG emissions compared to passenger cars (e.g., diesel, jet fuel).^17,18 Expanding reliance on heavy-truck freight could offset any gains in fuel efficiency, resulting in a net increase in GHG emissions by 2050.¹⁸ However, the costs of zero-emissions heavy-duty vehicles are changing rapidly.¹⁹

Similarly, the aviation sector could see a 50% increase in fuel use between 2020 and 2050 because of growing numbers of flights, even with advanced engine technologies.¹⁷ For example, the Federal Government’s Sustainable Aviation Fuel (SAF) Grand Challenge brings together the efforts of the Department of Energy, the Department of Transportation (DOT), the Department of Agriculture, and other federal agencies to reduce the cost, enhance the sustainability, and expand the production of SAF. This effort aims to produce SAF that achieves a minimum of a 50% reduction in life-cycle GHG emissions compared to conventional fuels and has a long-term goal of supplying sufficient SAF to meet 100% of aviation fuel demand by 2050.²⁰ Emissions-reductions efforts consider both CO₂ and non-CO₂ GHGs.¹⁷

Climate change and extreme weather events have a negative impact on transportation assets and human safety, often disproportionately affecting socially vulnerable populations (e.g., EPA 2021²¹). Examples of extreme weather events that caused significant transportation-related impacts in 2021 alone include debris flows and flooding after California wildfires, the winter storm in Texas, and Hurricanes Elsa, Florence, and Ida, which caused several deaths and billions of dollars in damages to the East Coast and Louisiana.²²

Strategies that incorporate climate data and projected future impacts into analyses to support the full range of transportation processes (planning and management of assets over their life cycles, to include considerations of design, construction, operations and maintenance, and user needs) have the potential to reduce risks and costs over the long term (Ch. 31; Figures 31.5, 22.15; KM 12.2). Failure to adapt the transportation network to the impacts of climate change could be costly (e.g., Chinowsky et al. 2013; Schweikert et al. 2015; Neumann et al. 2021^23,24,25). In particular, projected changes in temperature and precipitation, sea level rise, inland water level rise or fall, and storm surge are expected to significantly affect railroads, roads, ports, airports, and other transportation-related riverine and coastal properties in the United States (Ch. 12). Transportation planners are increasingly using analytical frameworks and tools to understand the vulnerabilities of their networks in pursuing a more resilient future (Table 13.1), although the focus on climate adaptation and resilience in transportation varies widely from region to region and state to state (KM 26.5).^26,27,28

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Table 13.1. Climate and Transportation Vulnerabilities

A selection of climate hazards and resulting transportation vulnerabilities are shown. Columns show selected climate hazards, and rows show individual transportation systems and the associated impacts on them. In some cases, possible adaptations to the vulnerabilities are included. Cells with few bullets represent the scarcity of research and not the lack of impact or vulnerability from climate hazards.

Transport Mode	Extreme Temperatures	Storms	Drought	Fire
Active transport (walking and biking)	Shift from active transport to vehicle or public transport29 Adverse health impacts for walkers and cyclists (KM 15.1)29	Shift from active transport to vehicle or public transport30 Obstructions and infrastructure damage30	Adverse health impacts for walkers and cyclists due to degraded air quality31	Shift from active transport to vehicle or public transport32 Reduced active transport due to short- and long-term health impairments32
Aviation	Runway damage from heat and thawing permafrost33,34 Altered flight schedules35 Increased insect activity and chance of bird strikes36,37,38	Coastal airport water intrusion34,39	Soil subsidence40 Increased dust storm risk41	Increased risk of flooding due to loss of ground cover vegetation42
Roadways	Cracking, buckling, and rutting from heat and permafrost thaw34,40 Unsafe working conditions (KM 15.1)33 Increased maintenance frequency43,44,45	Damage from flooding, erosion, saturated soil, and sea level rise (Ch. 9)34,40,43 Increased risk of landslides43 Reduced life cycle from repeated runoff events46 Travel lanes and bus routes blocked or rerouted due to flooding28	Reduced pavement integrity due to subsidence, collapsible soils, and increased groundwater pumping40,43 Reduced slope stability due to decreased roadside seeding uptake47 Emergency bridge maintenance48 Reduced visibility and increased closures from dust storms41	Road closures and reduced visibility40 Obstructions and debris flows (KM 6.1)49 Increased chance of runoff26,43 Reduced slope stability due to burn scar50
Rail	Buckling of rails (KM 5.1)34,40 Reduced train speeds51 Catenary line sag52	Flooding of bridges, tunnels, and low-lying rails33,34 Damage from landslides52	Changes in soil stability affecting track geometry and integrity53	Damaged equipment54 System disruption and rerouting54
Pipelines	Structural damage due to permafrost thaw (KM 5.1)55	Overloaded drainage systems40 Pipeline shifting, exposure, and fracture due to heavy precipitation34	Broken pipelines due to ground subsidence34	Fire-induced toxicity in plastic water systems56 Weakened pipelines due to increased runoff and debris flows57
Waterborne	Reduced problems with ice accumulation and increased access to ports (Ch. 10)34 Longer shipping seasons34	Port damage due to increased storm surges and tides34 River flooding34	Reduced vessel carrying capacity due to lower water levels34 Disrupted river transport due to inconsistent river flows (Chs. 22, 24)33,34	Disruption of port operations due to electricity and supply chain disturbances58,59

Tools and guidelines help organizations plan for the impacts of climate change, although individual agencies must still take the initiative to use them and challenge existing planning assumptions. Examples include the Federal Highway Administration (FHWA) Vulnerability Assessment and Adaptation Framework,²⁷ which can help transportation agencies assess their infrastructure’s vulnerability to extreme weather and climate impacts. Another is the US DOT’s Vulnerability Assessment Scoring Tool,⁶⁰ designed to help transportation planners conduct a quantitative, indicator-based screening of transportation system vulnerabilities to climate stressors, such as sea level rise, changes in precipitation, and higher temperatures. A 2021 study by the Transportation Research Board provided a risk-based decision support framework to inform quantitative methods for measuring resilience benefits.⁶¹ Additional research could help model asset deterioration and vulnerability. However, Colorado DOT and Utah DOT pilot studies followed similar risk-based frameworks.⁶¹

The FHWA has deployed multiple climate-resilience efforts, including the Resilience and Durability to Extreme Weather Pilot Program, to partner with state departments of transportation, metropolitan planning organizations, and others, with the goal of evaluating the vulnerability of regional transportation assets to extreme weather events.⁶² The Houston–Galveston Metropolitan Planning Organization participated in this pilot program and found that 13% of freeway miles and 12% of major road miles were highly vulnerable to flooding, storm surge, and sea level rise.⁶³

The FHWA pilot program also included the three-county Tampa Bay region in Florida—one of the country’s most inundation-vulnerable areas, with frequent storms and persistent flooding. The Hillsborough County Metropolitan Planning Organization found that when factoring in near-future projected sea level rise, 25% of major roads in the region could be impacted in a Category 3 hurricane.⁶⁴

Several state departments of transportation have used some or parts of these frameworks to perform detailed vulnerability assessments and to understand the condition of their assets and risks from climate threats. These efforts may also be driven by state legislation, such as in California and New York,^65,66 by bottom-up approaches at individual state and local agencies. The California Department of Transportation (Caltrans) found that 20% of bridges, 19% of large culverts, 20% of small culverts, and 18% of roadway segments assessed and managed by Caltrans were rated in the highest risk category. This indicates that a large proportion of Caltrans infrastructure is at risk of damage or destruction due to increased storm surge, extreme floods, cliff erosion, extreme temperatures, and effects of wildfires.^{43,67,68,69,70,71,72,73,74,75,76,77,78} California has recently mapped coastal transportation infrastructure vulnerable to 3 feet of sea level rise in Los Angeles and San Francisco and is considering a range of adaptation strategies, including nature-based solutions (Chs. 9, 28). Similar efforts have been completed by other states (including Washington, Tennessee, and Maryland) and subnational authorities.

Many agencies and organizations across the Nation have also initiated efforts to address the impacts of climate on a variety of transportation systems. While many of these are still in the initial stages of development, opportunities exist to improve on lessons state and local agencies have learned from the pilot programs at the local level (Ch. 12).^17,28,79

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Moving toward a decarbonized, climate-adapted, and resilient transportation system can be more than simply a response to the climate crisis. The 21st-century transportation sector is undergoing rapid transformation. The integration of cyber-technology and advances in autonomous and connected vehicles are changing the nature of what transportation systems are and how they operate. Transportation’s future is a complex, integrated, and dynamically shifting landscape marked by considerable uncertainty.⁸⁰ It faces unprecedented challenges from several sources: COVID-19; the growth of new technologies, business models, and opportunities; a massive shift to electrification; a changing logistics sector;^81,82 and significant workforce, diversity, and inclusion challenges. Cyber-vulnerabilities pose a profound challenge to the transportation industry^83,84,85 and communities, as well as national security risks. Figure 13.2 illustrates the complex relationship between the transportation sector, policy decisions and risk assessment, and future climate outcomes. Transportation system decisions made today have long-term implications for GHG emissions and climate adaptation. New tools and training have the potential to help navigate climate adaptation and disruption.

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A shifting transportation landscape, and how we respond to it, will determine future climate outcomes.

Figure 13.2. The ways people, goods, and services travel have changed since 1990, especially with the dramatic rise of internet traffic. These changes create new challenges, such as cybersecurity impacts, and, coupled with workforce and infrastructure resilience challenges, are increasing the policy decisions in transportation. These decisions will shape future climate outcomes. Figure credit: Open Society Foundations, Introducing Youth to American Infrastructure Inc., NOAA NCEI, and CISESS NC.

Frameworks are emerging to help decision-makers incorporate climate uncertainty into infrastructure planning.⁸⁶ Using available data and tools provided by technological advancements in other sectors such as computing, sensors, cyber-technology, and statistics, public agencies and private companies are creating greater awareness and, in many cases, taking action to address the uncertainty brought about by climate change on the expected use and lifespan of transportation systems and on the design, construction, operations, and maintenance of transportation-related infrastructure (Figure 13.3).

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Improving transportation resilience requires an iterative approach.

Figure 13.3. This concept demonstrates a potential iterative approach to planning, investing, and building for climate resilience in the transportation sector, starting with 1) integration of updated climate projections into guidelines and workflows and proceeding to 2) assessment of climate change–related risks, 3) prioritization of climate risk-mitigation investments and strategies, 4) implementation of prioritized strategies, and 5) ongoing tracking and reporting of progress, culminating with updates to enterprise asset management (EAM) data—the foundation for the next resilience cycle. This process is underpinned by a strong climate resilience policy. This approach is designed to ensure that the pursuit of resilience is ongoing, adaptable, and both immediately relevant and future focused. Figure credit: Port Authority of New York and New Jersey

Integrating climate data into engineering science is an emerging practice.^{26,87,88,89,90,91,92,93,94,95,96,97,98} Advances in tools used for the planning, design, and construction of transportation and infrastructure projects are further changing the state of the practice.^{92,95,99,100,101,102,103} The results of multiple years of climate research are beginning to see their way into transportation capital programming and project execution. Adaptation planning is beginning to recognize the challenges and opportunities of concurrent disruptors. For example, by harnessing low-cost heat and air quality sensors and increasingly accessible communication networks, researchers are showing the capabilities of informing active mobility users of high-exposure locations.¹⁰⁴ Decision-makers faced with evacuating large groups of people from extreme events can consider EV or non-traditional fleets. There is an ongoing effort, for example, to use EVs for powering buildings during outages.^105,106 Sensors that can detect climate hazards such as flooding and communicate risks to the public, or that can be integrated into existing intelligent transportation systems, are rapidly advancing.¹⁰⁷

Planning for adaptation concurrently with other disruptors will also require novel workforce capabilities. The transportation sector faces a number of workforce-related challenges, including aging, high retirement rates, retention issues, and industry-wide shortages for specific essential jobs; persistent underrepresentation of women and people of color; career awareness and image challenges impacting the attraction and recruitment of new employees; and significant technological impacts requiring further training and education related to the wider adoption of electric vehicles, information technology/cybersecurity risks, and increasing advances in artificial intelligence, robotics, and autonomous and connected vehicles.¹⁰⁸ As more employees gain the skills to navigate climate hazards, the sector will be better positioned to build resilience.^{27,109,110,111} The transportation sector can define the competencies needed for its future workforce and collaborate with educational programs (including universities, professional societies, and continuing education programs) to modernize training. Elevating human resources management as an important element of organizational risk and vulnerability assessment will help ensure that workforce development and readiness are an integral part of climate mitigation and adaptation efforts (KMs 5.2, 7.3, 11.3, 16.2, 20.6; Ch. 29). The sector would further benefit from “K to gray”—a multipronged strategy that recognizes the importance of employee and workforce development and readiness at all levels and ages.¹¹²

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A carbon-free, sustainable, and resilient transportation system would have societal benefits beyond reduced climate change impacts, potentially leading to improvements in air quality, physical fitness, incidence of cardiovascular and respiratory disease, mental health, crash rates, noise pollution, social equity, ecosystems, biodiversity conservation, energy independence, and the economy.^113,114 When these co-benefits are considered, the benefits of GHG mitigation actions in the transportation sector far outweigh the costs (Figure 13.4).¹¹⁵ Considering the impacts for different population subgroups can also ensure that these actions improve environmental, health, and social equity. These societal co-benefits would be particularly powerful in urban areas, where large numbers of people are experiencing elevated air pollution, health inequities, heat stress, traffic congestion, long commutes, and the negative health consequences of a sedentary lifestyle (Ch. 12). In contrast to the long-term and planetary-scale impacts of reducing GHGs from the transportation sector, these societal benefits would accrue immediately and locally, wherever the transportation emissions changes are implemented.

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Decarbonizing transportation could save money and improve air quality, social equity, and the health of people and ecosystems.

Figure 13.4. Integrating mitigation and resilience into transportation policies and planning at multiple scales leads to improved air quality, enhanced physical fitness from cycling, reduced environmental injustice as a result of decreases in heavy-duty trucking and idling, healthier ecosystems, and more economic opportunities. Figure credit: George Washington University and Jacobs.

The benefits of infrastructure and transportation resilience are also well documented and include increased reliability; lower costs to travelers, industry, and consumers, as well as to owners and operators of transportation infrastructure; improved safety and better health outcomes for workers and travelers; and the ability to support evacuations (KM 22.3).^{116,117,118,119,120} However, significant resources are necessary to ensure the continued benefits and state of good repair of sustainable and climate-resilient transportation systems for all communities.¹⁰²

Reducing GHGs in the transportation sector would also achieve co-benefits from improvements in air quality, climate and environmental equity, and physical fitness, as well as reduced incidence of cardiovascular disease, diabetes, and cancer (Figure 13.4; KM 12.3; Chs. 14, 24, 32)—all of which could counteract some climate impacts on human health (Ch. 15). Given the significantly high economic cost of air pollution in the United States, the monetary value of these benefits would be substantial.¹²¹ Traffic-related emissions are a significant contributor to air pollutants, particularly fine particles (PM_2.5), ozone (O₃), and nitrogen dioxide (NO₂), all of which are associated with higher rates of illness and death.^{122,123,124,125,126} In addition, emerging evidence suggests that exposure to elevated CO₂ levels indoors impacts cognitive function.¹²⁷ Reducing outdoor CO₂ emissions from the transportation sector could also reduce indoor CO₂ levels.¹²⁸

Fuel efficiency, more stringent vehicle emissions standards, reduced passenger vehicle traffic, vehicle electrification, and mode switching to public transportation and walking or biking would result in co-benefits from improved air quality and better health. Modeling studies show that vehicle electrification reduces mortality related to PM_2.5 and O₃, even when considering increased emissions from additional energy demand.¹²⁹ However, increased energy use from demand for electricity, lithium mining, and potentially heavier vehicles can offset some of these air quality improvements when electricity generation is from burning fossil fuels, highlighting the importance of transitioning to non-combustion electricity generation, such as from renewable energy sources (KM 13.4; Ch. 12).

COVID-19 lockdowns provided an unprecedented opportunity to examine how reduced passenger vehicle activity (and increased telework and bike use) affected CO₂ and air pollution. CO₂ emissions dropped by about 32% in April 2020 but rebounded to near normal by 2021, indicating that lifestyle changes (such as those experienced during the pandemic) must be coupled with transformative changes in transportation systems to reach GHG emissions-reduction targets (Focus on COVID-19 and Climate Change). In terms of air pollution, many cities experienced dramatic reductions in NO₂ pollution,^130,131 although impacts on PM_2.5 and O₃ were much more variable and location dependent.¹³² Because traffic-related air pollution is inequitably distributed within US cities,^131,133 moving toward a carbon-free transportation system would also advance environmental and health equity. For example, air pollution inequity would be reduced through vehicle electrification, improved fuel efficiency, and structural actions to reduce vehicle-miles traveled for moving people and goods, such as changing the design of cities and increasing reliance on emissions-lowering modes, increasing public transportation use, and moving freight by rail rather than by road (Ch. 12). Walking or cycling instead of driving improves physical fitness and overall health,^{115,134,135,136} and steps could be taken to ensure that safe access to these active transportation modes is available equitably across social groups. Active transportation and more time in natural environments also have mental health benefits, including improved cognitive function and well-being.¹³⁷ Reduced vehicle traffic also leads to fewer crashes and injuries.¹¹⁵

In recent years, several decision support tools have been developed to quantify and value the multiple benefits of actions that reduce transportation GHG emissions, including the Integrated Transport and Health Impact Model¹³⁸ and the Health Economic Assessment Tool for walking and cycling.¹³⁹ Integrating co-benefits into transportation policies and planning at multiple scales (e.g., neighborhood, urban, national) can create additional appeal for reducing transportation-sector GHG emissions for both decision-makers and the public. Key Messages 13.1 and 13.2 provide context on how to consider uncertainties in these decisions.

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The need for climate mitigation and adaptation has created an opportunity to rethink transportation systems and land use at all levels. Still, such transformations (or decisions to maintain the status quo) may include some risks, with benefits sometimes accompanied by adverse or uncertain impacts (KM 13.2; Ch. 12). Political and policy actions in the US are generally based on compromise among an array of interests, which may lead to trade-offs that fall short of idealized climate mitigation or adaptation actions. Moving toward equitable climate resilience and environmental justice via a just transition requires that consideration of such trade-offs be addressed through the full participation of relevant communities (Chs. 16, 31; KM 22.3).¹⁴⁰ Environmental justice also requires that trade-offs be managed in ways that address community self-determination,^141,142 as well as the needs of communities that are affected by transportation infrastructure and the impacts of the existing built environment or that currently lack reliable, sustainable, and affordable transportation services (Figure 13.5; Chs. 11, 17).^106,143,144

Adopting alternative energy sources to reduce transportation emissions from fossil fuels has enormous potential for direct GHG and air pollution reduction, as well as opportunities for a just transition, but also includes potential risks or trade-offs. For example, battery production for EVs is mineral-intensive, requiring large quantities of lithium, nickel, copper, tantalum, and other minerals. Mining these raw materials may result in environmental degradation, public health harms, or displacement of nearby communities, as well as cultural impacts, including loss of sacred spaces.^145,146 Potential risks associated with adopting alternative energy sources should be considered in the context of current trade-offs related to existing energy sources, including the well-documented environmental and global climate change effects and adverse human health impacts resulting from the use of internal combustion–engine vehicles and fossil-energy power plants (KMs 5.2, 12.2). The siting of power-generation facilities, including utility-scale renewables, can have similar impacts. Experts have also noted that used batteries and electronic components pose the problem—and the opportunity—of repurposing, recycling, and disposal,¹⁴⁷ which researchers are currently working to address. Vehicle power source changes can also affect the distribution of road-user fees;¹⁴⁸ preferential registration fees are designed to signal preferences for one power source over another. Both of these revenue strategies could entail transportation funding trade-offs. The transition to zero-emissions vehicles may result in only localized air pollution reductions (KMs 13.3, 14.5).^149,150

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Reducing emissions involves trade-offs that have implications for reliability, equity, and environmental quality.

Figure 13.5. This figure shows many of the considerations where risks may arise as changes are made to transportation systems. Each tab on the figure represents a potential trade-off to all of the other factors shown. For example, changing transportation fuels or moving to electric drivetrains can decrease greenhouse gas and air pollutant emissions but may also affect transportation availability (which includes both geographical location and affordability) and reliability in underserved communities or in communities adapting to changing climates. Further, mining of raw materials for those technologies has the potential to damage ecosystems and cultural or sacred landscapes. Accordingly, decisions about climate mitigation and adaptation in transportation systems should be carefully considered through lenses of environmental justice and community self-determination. Figure credit: EPA and University of Idaho.

Climate adaptation actions entail consideration of trade-offs. For example, moving a coastal roadway inland to avoid sea level rise (i.e., managed retreat) may not allow for an immediate modal shift, but it may provide an opportunity to reconsider the size and capacity of the roadway and also allow for landscape restoration along the original alignment, as illustrated by the Highway A1A Redesign Project in Fort Lauderdale, Florida, and the Piedras Blancas Highway 1 Realignment project in San Luis Obispo, California (Ch. 9).^151,152

For the freight transportation system, equitable distribution of trade-offs under a climate change framework will also require particular attention. In addition to turning over vehicles and equipment to lower-emissions or zero-emissions technologies, there are opportunities to obtain energy savings and emissions reductions by shifting freight from road transport to rail or water. Further infrastructure development will be necessary to make such mode shifting more viable.

Changing the geographical footprint of freight systems also brings up trade-offs. Inland port facilities can receive and manage cargo that has been unloaded from a seaport some distance away and transported via low-polluting transport modes (in terms of tailpipe and full-life-cycle air pollutant and GHG emissions, such as electric or hybrid locomotives or trucks) or highly efficient modes (energy use per cargo per mile, such as rail), or both, with the potential to boost system efficiency and reduce air pollutants and GHG emissions and reduce exposure to air pollutants in communities near seaports.¹⁵³ However, people living near such inland freight facilities could in turn experience increased traffic, air pollution, and environmental damage, creating or exacerbating environmental injustice. Emissions inventory methodologies can help to quantify these impacts and enable affected communities and decision-makers to develop emissions-reduction strategies from different activities and/or equipment types (Focus on Risks to Supply Chains).^154,155

Trade-offs related to the freight workforce are also becoming clear. For example, independent truck owner-operators, who do not work for a larger employer and own their own trucks, may not have the resources to purchase and operate cleaner vehicles or have access to appropriate fueling or charging infrastructure.^156,157

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