Accelerating Decarbonization in the United States: Technology, Policy, and Societal Dimensions (2024)

9

Transport

ABSTRACT

Transportation emissions represent nearly one-third of greenhouse gas (GHG) emissions in the United States, the majority of which will be reduced through vehicle electrification. The costs to produce, purchase, and operate electric vehicles (EVs) have fallen significantly, due primarily to reduced battery costs and total costs of ownership, and are now reaching parity with comparable internal combustion engine models. The Infrastructure Investment and Jobs Act (IIJA)¹ (2021) and the Inflation Reduction Act (IRA) (2022) have provided historic levels of funding and tax credits to address climate change. Despite this legislation, there remain barriers to reaching zero-emission vehicle (ZEV) sales goals for light-duty vehicles (LDVs), including consumer reticence about current EV initial cost premiums over internal combustion engine vehicles (ICEVs), lack of awareness about available incentives for EV purchase and home chargers, insufficient overall funding for public chargers to enable EV use for drivers without home charging and for those making trips longer than their vehicle range, and constraints on critical minerals for EV batteries. Requirements in the IRA itself regarding battery minerals sourcing and North American manufacturing have reduced the number of models qualifying for tax credits, although it is not clear how quickly automakers will adapt in the near term. Midpoints of projections suggest that the United States may not achieve its goal of 50 percent ZEV sales by 2030. Even if it does, long-distance, heavy-duty (HD) land transport; aviation; and marine vessels will require development and large-scale production of net-zero carbon liquid fuels for successful decarbonization by 2050 and beyond.

Given the current technological and policy situation for transportation decarbonization, the committee recommends actions to help achieve ZEV sales goals, including continued tightening of federal fuel economy and emissions standards; federal and state adoption of California ZEV sales mandates; additional incentives for vehicle purchase and charger installation; and local funding and policies preferencing EVs and chargers (Recommendation 9-1). The committee also recommends cost-effective electrification of port and airport operations (Recommendation 9-2); cost-effective state and local policies to reduce vehicle emissions through enhanced

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¹ Also referred to as the Bipartisan Infrastructure Law (BIL).

traffic management and operational efficiency; substitution of information technology for travel (especially via aircraft); expansion of transit and non-motorized travel; and land use changes to enhance the density of development (Recommendation 9-3). To decarbonize the embodied carbon in infrastructure, the committee recommends state and private standards and procurement policies to reduce the carbon content of infrastructure materials and carbon emissions during construction and maintenance (Recommendation 9-4). To enhance equity, the committee recommends state and local efforts to support EV purchase by low-income households and equitable distribution of chargers; targeted expansion of transit, car sharing, and other modal options for those unable to afford EVs; and representation of low-income residents on public planning, zoning, and transportation decision-making boards (Recommendation 9-5). Last, the committee recommends that targeted federal investments in research, development, and demonstration (RD&D) be made to improve battery and fuel cell design and performance and production of net-zero liquid fuels for hard-to-decarbonize modes such as aviation, ocean shipping, freight rail, and long-distance heavy trucks (Recommendation 9-6).

INTRODUCTION

Transportation is the nation’s largest source of GHG emissions, accounting for 29 percent of total GHG emissions, edging ahead of electric power generation (25 percent) in 2019 (EPA 2021). On-road vehicles (automobiles and trucks) dominate transport GHG emissions (82 percent) (Figure 9-1 and Table 9-1).² Within that group, LDVs (58 percent) emit the largest share of GHGs because of the large stock of 260 million LDVs driving more than 3 trillion vehicle miles per year.³ Medium- and heavy-duty vehicles (MHDVs) (24 percent), including trucks moving about half of the nation’s freight (BTS 2021b), are the second largest emitters from a stock of 13.2 million vehicles moving almost 2.5 trillion ton-miles per year. Aviation for freight and passenger transportation (10 percent) is the third largest, although aviation’s GHG emissions alone considerably understate its adverse climate forcing effects (Lee et al. 2021).

The majority of GHG emissions from transportation results from combustion of fossil fuels onboard vehicles in internal combustion engines. A primary target for deep decarbonization is vehicle electrification, which eliminates onboard vehicle GHG

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² Note that these estimates of total transportation emissions do not include estimated methane leakages from pipelines, which recent studies (Von Fischer et al. 2017; Weller et al. 2020) are finding to be much more substantial than previously believed.

³ LDV and MHDV stock estimates from EIA (2022) Tables 39 and 49. LDV vehicle miles and truck ton-miles from Bureau of Transportation Statistics (2021a,c), Tables 1-35 and 1-50.

emissions, uses energy more efficiently to move the vehicle, and allows energy use from lower-emitting sources of electricity that reduces life-cycle emissions relative to use of fossil fuels. Electrification takes on many forms for efficiency and emissions reduction. Hybrid electric vehicles (HEVs) are powered by combusting liquid fuels in an efficient powertrain that harvests electrical energy from regenerative braking, which is stored in a battery and used to supplement engine power. Plug-in hybrid electric vehicles (PHEVs) are similar to HEVs, but they have larger batteries, motors, and other electrical equipment that allow for the vehicle to be charged with electricity from the grid and travel on stored power for a typical range of up to 30–50 miles in addition to efficiently operating with an internal combustion engine. Battery electric vehicles (BEVs) are of most interest for deep decarbonization because their entire motive power comes from grid electricity stored in an onboard battery. Fuel cell electric vehicles (FCEVs) are powered via fuel cells, which oxidize fuels (usually hydrogen) stored onboard the vehicle and can aid deep decarbonization if the hydrogen source has low-carbon emissions.⁴ This chapter refers to plug-in electric vehicles (PEVs) as

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⁴ This report considers low-carbon hydrogen as defined in the IIJA §40315: hydrogen with a carbon intensity of less than 2 kilograms of CO₂ equivalent per kilogram of hydrogen at the site of production. The Department of Energy (DOE) has also released a Clean Hydrogen Production Standard with a life-cycle-based target of well-to-gate carbon intensity of less than 4 kg CO₂ equivalent per kilogram of hydrogen (DOE 2023b).

TABLE 9-1 Transportation GHG Emissions (2019)

^a Off-road vehicles, such as those used in construction and agriculture, add 11 percent more GHGs from fuel combustion in internal combustion engines (Ledna et al. 2022). SOURCE: EPA (2021).

the combination of BEVs and PHEVs. It refers to ZEVs as any vehicle type that has zero carbon tailpipe emissions—for example, BEVs and FCEVs.

This chapter begins with a focus on transportation electrification, describing the committee’s 2030 ZEV sales goals, supportive policies (including describing the measures in the IIJA and IRA that support the committee’s first report goals for electrifying roadway transportation by 2030), and the barriers that remain in achieving them. The other sections go on to identify and describe other important transportation decarbonization opportunities and challenges, including reducing GHG emissions through increased efficiency of travel and reduced carbon content of infrastructure materials, construction, and maintenance (see the section “GHG Reduction Through Transport Efficiency”); crosscutting issues such as equity, PEV demand on the electric grid, and agricultural and carbon sink constraints on bio-fuel production (see the section “Equity and Other Crosscutting Issues”); and innovation priorities for RD&D (see the section “Actions to Expand the Innovation Toolkit”). Table 9-5, at the end of the chapter, summarizes all the recommendations that appear in this chapter regarding decarbonizing the transportation system.

TRANSPORTATION ELECTRIFICATION INCLUDING ZEV SALES GOALS, SUPPORTIVE POLICIES, AND BARRIERS

Light-Duty PEVs and Charging Infrastructure

LDV Goals and Scenarios

LDVs are increasingly being electrified owing to market demand, corporate offerings, and incentives offered for electrification and its attributes, primarily fuel efficiency and reduced emissions. In its first report, the committee recommended specific goals for decarbonizing transportation (NASEM 2021a):

• A national standard for a 50 percent sales share of ZEVs by 2030 and 100 percent by 2050. (The U.S. national long-term decarbonization strategy also sets a 2030 goal of 50 percent EV sales [DOS and EOP 2021].)
• Deployment of public charging infrastructure to meet charging needs, which it estimated to be at least 3 million Level 2 chargers and 120,000 fast direct current (DC Fast) chargers by 2030.⁵
• An investment goal of $5 billion for intercity charging infrastructure.

Based on its updated findings presented in this report, the committee continues to endorse these goals for light-duty (LD) ZEVs and charging infrastructure from its first report, and provides further goals, especially described in Finding 9-1 and Recommendation 9-1. Note that while the committee endorses ZEVs (BEVs and FCEVs) as the appropriate goal for deep decarbonization of road transportation, it may be appropriate to incorporate or even encourage PHEV deployment in some limited amount, especially in the early stages of decarbonization (Foster et al. 2022). Most federal and state incentives and regulations currently incorporate PHEVs, with consideration of their remaining emissions, into ZEV regulations.

Long-term investment in RD&D by the public and private sectors, especially in batteries, provided breakthroughs in EV technologies that are driving down their costs and helped stimulate more than $1.2 trillion in North American and European original equipment manufacturer (OEM) investment commitments to PEVs (Leinert 2022). Well before passage of the IRA, automakers announced multiple new EV models, including LD pick-up trucks and sport utility vehicles (SUVs) (Car and Driver 2022). Many automakers have announced corporate decarbonization or electrification goals and commitments. (See Table 9-4 below.) Similarly, major investments in manufacturing

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⁵ Level 2 charging provides roughly 25 miles of driving per hour of charging. DC Fast charging provides roughly 100 to 200 miles of driving per half hour of charging (DOE n.d.(a)).

capacity for EVs were planned before passage of the IRA, including adding 13 new EV battery manufacturing plants (DOE 2021; Voelker 2021). The appeal of personal PEVs to high-income households has already been proven; hence, the emphasis in the IRA on stimulating PEV purchases by low- and moderate-income households to accelerate and broaden penetration of PEVs into the vehicle fleet.

Demand for PEVs has increased sharply since 2020, reaching 6.8 percent of LDV sales in 2022 (Table 9-2), with corresponding reduction in GHG emissions (Figure 9-2). Meeting the LD ZEV 2030 sales goal would require a roughly 130 percent annual growth rate from 2023 to 2030 (Table 9-2)—an ambitious but achievable goal. LD PEV sales in China and Europe reached more than 15 percent of total LDV sales in 6 years by 2021 (IEA 2022a), which is comparable to what the United States would need to accomplish in the 6 years starting in 2023 to be on a trajectory to achieve a 50 percent sales share of ZEVs by 2030 (Table 9-2).

TABLE 9-2 Estimated Zero-Emission LDV Sales Growth Required to Reach 50 Percent of LDV Sales by 2030, and the Resulting Stock of Zero-Emission LDVs

NOTES: ZEV sales and stock estimated based on growth rates needed to achieve the committee’s ZEV sales goal. The initial 2021 and 2022 data are the actual sum of PEV sales in the United States—a mix of PHEVs and BEVs—and the very small number of FCEV sales, including the share of total sales and total LDV stock based on EIA (2022), Table 39. To reach the committee’s ZEV sales goal, future projections assume a continued trend of declining share of PHEVs toward BEVs and FCEVs. SOURCE: Based on data from the U.S. Energy Information Administration, March 2020 (EIA 2022).

The LD PEV and FCEV and charger tax credits in the IRA and the funding authorized and appropriated for charging infrastructure and other transport electrification in the IIJA will accelerate demand for PEVs.⁶ The IRA also provides substantial tax credits to North American manufacturers of vehicles and batteries through 2032, and for production of low-carbon and net-zero liquid fuels, which will stimulate supply. Production of low-carbon and net-zero liquid fuels may help reduce future GHG emissions from the large post-2030 stock of LD ICEVs, long-distance heavy freight vehicles and vessels, and aircraft.

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⁶ It should be noted that federal legislation, such as the IIJA, IRA, and CHIPS and Science (CHIPS), contains different funding mechanisms. The IRA primarily consists of spending programs (appropriations) and tax expenditures. Spending programs can allocate federal resources to projects and activities up to the amount of their appropriation. By contrast, tax expenditures, such as the production tax credits in the IRA, typically have no limit on the amount that could be claimed by taxpayers. The IIJA consists of a mix of authorizations and appropriations, while CHIPS contains primarily authorizations. Authorizations are laws that establish or continue a federal program or agency and are typically passed by Congress for a set period of time, but authorizations require an appropriation before funds can be spent. Appropriations are laws that actually provide the money for government programs and must be passed by Congress every year in order for the government to continue to operate.

Whether demand will grow as fast as required to reach a 50 percent 2030 ZEV sales goal is uncertain and unknowable at this point. An analysis compared several economy-wide models of the impacts of the IRA versus reference scenarios, with five models including projections of EV sales share for LDVs. The cross-model comparison found that provisions in the IRA resulted in a projected 32–52 percent (41 percent average) of new LDV sales being EVs by 2030, as compared to 22–43 percent (31 percent average) in the reference scenarios (Bistline et al. 2023). The Energy Innovation and Princeton Zero Lab research groups each produced reports estimating LD and MHD EV sales based on implementation of the IRA alongside other mid-range policies, including the California emissions standard adoption by 17 states and the District of Columbia, and find, respectively, 48–61 percent LD and 39–48 percent HD EV sales (Slowik et al. 2023) and 52 percent LD and 58 percent MHD EV sales in 2030 (Jenkins et al. 2023). State and local policies discussed later in this section and in the section “GHG Reductions Through Transport Efficiency” can further stimulate ZEV demand toward achieving 2030 sales goals.

In addition to providing incentives for EV deployment, provisions in the IRA change eligibility of vehicles and buyers for tax credits, in some cases restricting eligibility, and in other cases expanding it. The IRA’s requirements for North American LDV assembly; sources of battery minerals; mineral processing facility locations; and battery manufacturing facilities; as well as limits on the price of qualifying vehicles (§13401)⁷ have reduced the number of PEV models eligible for federal tax credits. However, the law also expands the number of eligible vehicles by removing limits based on manufacturer volume and allowing used vehicle sales to qualify for tax credits. The law limits the buyers eligible for tax credits based on an income cap, aligned with a recent recommendation by the National Academies (NASEM 2021b), but also expands who is eligible, allowing the tax credit to be transferred to the dealer, who can pass along savings to buyers who do not have tax liability, or prefer an immediate cost reduction. All of the above IRA provisions, however, only apply to individual vehicle sales governed by Internal Revenue Code section 30D. Commercial vehicle sales, which include leased vehicles, are covered under different tax provisions (section 45W) and do not have any mineral sourcing, battery assembly, or income/price eligibility limits. It is not clear how the IRA’s changes to tax credit eligibility for individual and commercial vehicle sales will affect vehicle supply and

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⁷ Eligibility for federal LDV tax credits require vehicle assembly in North America; 40 percent of battery minerals sourced or processed in the United States or U.S. trading partners with free-trade agreements in 2023 and 80 percent by 2026; and 50 percent of battery assembly in North America in 2023 and 100 percent by 2028. Income eligibility is capped at $300,000 adjusted gross income (AGI) for couples filing jointly and $150,000 AGI for individual filers (CRS 2022).

demand in the next few years, as automakers develop supply chains, build new battery factories, and change vehicle offerings so that their customers can capture tax credits. More details on the impact of critical minerals and materials on EV supply chains and tax credits are covered in the section “Barriers and Supportive Policies to Electrify Roadway Vehicles.”

Charging Infrastructure

The $7.5 billion in funding authorized and appropriated for chargers in the IIJA (§11401 and Division J, Title VIII) will provide roughly 500,000 chargers (mostly on intercity highways) and make significant progress toward the total chargers needed to reach the committee’s 2030 goals. Although most PEV charging in early deployment markets like Europe and California has been done either at home (50–80 percent) or workplaces (15–25 percent for owners that have a vehicle commute) (Hardman et al. 2018; NASEM 2015), prospective U.S. BEV buyers express concern about the lack of public charging stations (Consumer Reports 2022a). As of the first quarter of 2023, there were about 104,000 Level 2 workplace and public charging ports (at 46,000 locations), and about 30,000 DC Fast charging ports (at 7,000 locations) (Alliance for Automotive Innovation 2023)—far short of the 3 million the committee estimates will be needed by 2030.

Medium- and Heavy-Duty PEVs and Charging Infrastructure

The committee’s ZEV sales goals include MHD trucks reaching 30 percent of sales by 2030. The market for PEVs is much more established for LDVs than for commercial MHD trucks. Roughly 2.3 million LD PEVs were registered in the United States by the end of 2021 (Alliance for Automotive Innovation 2022b, p. 7), compared with only 1,200 MHD BEV or FCEV trucks (Al-Alawi et al. 2022). Although lagging behind the personal vehicle EV market, several OEMs have MHD truck PEV models in development, and Tesla has produced a limited number of long-distance HD PEVs with capabilities that could prove consequential for HD truck PEV demand if proven in early use (Sriram 2022).

Commercial PEVs should be attractive to operators of local MHD trucks that can run a full day on a single charge and recharge at home-base depots overnight. The IRA (§13403) provides tax credits for purchase of commercial PEVs and FCEVs, representing the lesser of up to $40,000 or 30 percent of the purchase price for MHD trucks. The 30 percent subsidy of the purchase price of MHDs in the IRA could drive a 40 to 50 percent PEV sales share of MHD trucks by 2035 (Linn and Look 2022; Slowik et al. 2023).

Expansion of existing state efforts to subsidize fleet owner purchases of BEV trucks and chargers would also accelerate demand, as will the Environmental Protection Agency’s (EPA’s) 2023 approval of the California Air Resources Board’s (CARB’s) Advanced Clean Trucks (ACT) regulation. Among other provisions, this rule requires roughly half of new truck sales (40 percent of HD trucks) to be ZEVs by 2035. In April 2023, CARB petitioned EPA to allow enactment of a more expanded MHD truck ZEV rule that would phase out use of ICEVs by 2045 (CARB 2023).

Recent scenarios for needed MHD PEV chargers suggest a total investment requirement of $21 billion to $79 billion by 2030–2035 based on varied scenarios of fleet penetration and charger type installed.⁸ The IRA’s tax credits for commercial chargers (§13404) cover a maximum of 30 percent of cost, or $30,000 at each separate location, which expand to up to $100,000 if prevailing wage and apprenticeship criteria are met. Given these tax credits and the fuel and maintenance cost savings that truck BEVs are expected to provide commercial owners, the cost of chargers should not be a barrier for short-haul plug-in commercial MHD trucks.

Although representing about 10 percent of MHD trucks, long-distance HD trucks account for about half of MHD truck GHG emissions (Ledna et al. 2022). Large-scale electrification of long-range HD trucks, and associated charging requirements, remains uncertain at this time owing to the large batteries required with associated high demand for battery minerals, and heavy power and energy demand on the electric grid (Katsh et al. 2022; Slowik et al. 2023). Slower charging may also be an alternative to reduce power demands, but may be a deterrent for adoption of electric freight vehicles if they need to charge in the middle of their trips, impacting drivers’ time on the road. Slowik et al. (2023) project that if these requirements could be met, the IRA could increase the sales share of HD, long-range trucks up to 17 percent by 2035 (see Slowik et al. 2023, Figure 7). Burnham et al. (2021) estimate that with aggressive assumptions about technology advancement, the total cost of ownership of HD PEV trucks could be competitive with ICEVs by 2035 (see Burnham et al. 2021; Figure 4-8).

Importance of Achieving 2030 ZEV Sales Goals

Achieving or approaching the committee’s 2030 sales goal of 50 percent ZEVs is a central element of decarbonizing transportation by 2050. Doing so would quickly achieve the scale economies necessary to bring down the cost of ZEVs and create sustainable markets for private providers of charging infrastructure. More importantly,

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⁸ Estimated from McKenzie et al. (2021) and Phadke et al. (2021).

illustrative stock turnover scenarios for LDVs indicate that meeting a sales goal of 100 percent ZEVs by 2050 with no interim sales goal leads to a fleet in 2050 that still has 46 percent ICEVs (Figure 9-3), which would require significant volumes of fossil fuels and produce large amounts of GHG and other emissions. In contrast, meeting an interim 2030 goal of 50 percent ZEV sales as well as a 2050 goal of 100 percent ZEV sales would lead to a vehicle stock in 2050 that is about 10 percent ICEVs and 90 percent EVs. If the goal of 100 percent ZEV sales is further advanced to 2035, then there will be close to zero ICEVs operating, requiring fossil fuels, and producing emissions, in 2050. Any legacy ICE LDVs—combined with hard-to-electrify-transport vehicles such as aircraft, ships, locomotives, and long-distance heavy trucks—would continue to demand liquid fuels at a scale that would make it very challenging to fully decarbonize the transport sector by 2050 for reasons discussed in the sections “Equity and Other Crosscutting Issues” and “Actions to Expand the Innovation Toolkit” below, as well as in Chapter 8. Thus, it may be necessary to reduce the legacy stock of ICEVs even faster than would be accomplished by achieving the 50 percent 2030 ZEV sales share. One option for reducing the legacy stock of ICEVs is to accelerate scrappage of vehicles; however, as noted by the National Academies (2021b), the effectiveness and impacts of accelerated scrappage programs are not well understood and should be

studied with respect to their benefits of emissions reduction, increasing ZEV sales, and addressing equity considerations as well as program costs.

Low and net-zero carbon liquid fuels are a possible route to decarbonization of vehicles, both for older legacy vehicles during the phase-out of combustion engines as well as for harder to electrify transportation subsectors. Cost-competitive net-zero carbon fuels at scale, while feasible, do not yet exist (NASEM 2021b). With innovation and either an explicit or implicit carbon price or regulation, cost-competitive net-zero carbon fuels may become available in the future, but today’s options for low-carbon fuels are currently lacking. The actual carbon content of current low-carbon fuels on a full life-cycle basis varies considerably across feedstocks and is subject to uncertainties especially in the case of biofuels (NASEM 2022b). Sustained research and development (R&D), innovation, and demonstration at scale is required in order for truly net-zero carbon liquid fuels to contribute substantially to transport GHG reductions in the future (see the sections “Equity and Other Crosscutting Issues” and “Actions to Expand the Innovation Toolkit”). Such fuels will still be limited in use owing to concerns about biofuel production competing for land with agriculture and forest and marginal lands needed for carbon sinks (Chapter 8), and their harmful air pollution impacts, especially for environmental justice communities that are disproportionately impacted by vehicle emissions.

Barriers and Supportive Policies to Electrify Roadway Vehicles

Three important barriers to accelerated LD PEV market penetration remain: consumer discounting of vehicle operating cost savings, current lack of public charger availability, and manufacturer access to critical minerals and materials, especially within the context of IRA incentives. These barriers, and supportive policies to overcome barriers, are discussed next.

Barriers in Consumer Cost and Valuation of Electric Vehicles

Cost is one of the main considerations for vehicle market decision-making. Production costs⁹ for PEVs and ICEVs are important inputs to the decisions of vehicle producers and sellers. Purchase and operating costs are important inputs to decisions of vehicle

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⁹ This section discusses vehicle costs, rather than vehicle prices, because vehicle costs offer a more fundamental comparison between PEVs and ICEVs. Vehicle costs are fundamental expenses, such as the cost of materials, labor, and capital to produce a vehicle, or the cost of fuel, supplies, and labor to operate and maintain a vehicle. Vehicle prices are impacted indirectly by the same fundamentals that underlie vehicle costs, as well as by additional variables such as automaker and vehicle dealer market strategies to influence sales of different models.

buyers and users. PEV production costs have been falling in comparison to rising costs of ICEVs owing to technology developments in BEVs, particularly the dramatically falling costs of batteries, and efficiency, safety, and other regulations impacting both ICEVs and PEVs (NASEM 2021b).

Two cost-parity points may be particularly salient for consumer decision-making: (1) first-cost parity, when purchase prices of PEVs and ICEVs are equal, and (2) total cost of ownership (TCO) parity, when the costs to purchase and operate PEVs and ICEVs are equal. The most recent National Academies’ study of LDV efficiency technology estimates first-cost parity by 2025–2030 for manufacturers producing high volumes of EVs (NASEM 2021b). TCO parity is likely already present for some PEV models relative to comparable ICEVs and will be present by 2025 for additional models (Lutsey and Nicholas 2019). Going forward, PEVs will begin showing considerable cost savings owing to electric drivetrains that require 70–80 percent less energy to operate, less expensive fuel (electricity), and reduced electric drivetrain maintenance compared to ICEVs (DOE n.d.(c)). PHEVs are not projected to reach first cost parity with ICEVs in the 2030s because they contain significant aspects of both BEV and ICE powertrains, so have comparatively higher costs than BEVs (Lutsey and Nicholas 2019; NASEM 2021b).

Despite cost reductions, consumers do not show consistent behavior in purchasing vehicles based on TCO. It is not clear why this is the case, but it may be because consumers are unfamiliar with or inattentive to vehicle operating costs, that they value other vehicle attributes like acceleration or vehicle size, that they see predicted fuel savings as a “risky bet” that may not come to fruition with their vehicle purchase, or that TCO it is not communicated in a way that consumers can use, such as monthly cost of ownership comparisons (Dumortier et al. 2015; Greene 2011, 2019; Leard 2018; NASEM 2021b). Past battery reliability issues with certain vehicle models, and low reliability ratings for new electric SUV models, likely contribute to concerns about capturing maintenance cost savings (Consumer Reports 2022b). Consumer perception of first-cost parity is also impacted by the availability of purchase incentives from federal and state governments, which effectively reduce PEV purchase price for many consumers.

Even when faced with PEVs that are less expensive to produce and purchase than ICEVs, consumers may still see lack of charging infrastructure, cost of installing Level 2 chargers at home, or lack of model and product diversity as barriers to individual purchase decisions (Consumer Reports 2022a; NASEM 2021b). Passenger safety of electric vehicles appears comparable to conventional vehicles (IIHS-HILDI 2021), and thus does not appear to be a major consumer vehicle purchase consideration.

Charging Infrastructure Barriers

As discussed above, IIJA funding authorized and appropriated for public chargers and IRA tax credits for chargers may fall short of the amount required to achieve 2030 sales goals. Whether private investment in charger installation, operation, and maintenance will close the gap in time to meet 2030 sales share goals is unclear.

Shared charging stations for individuals without dedicated parking spaces will be needed to enable widespread electric vehicle adoption. About one-third of homeowners do not have a garage or carport that could be used for charging, but when renters are included 44 percent of households lack residential charging capability (Consumer Reports 2022a; DOE-VTO 2022). IRA §13404 provides substantial tax credits (estimated to total $1.7 billion through 2032) for home installation of chargers and to encourage siting of commercial charging stations in low-income or non-urban areas (CRS 2022).

Estimates of the funding required by 2030–2035 for LD charging infrastructure of all types (residential, workplace, and public) range from roughly $73 billion to $87 billion.¹⁰ The estimated investment requirements for single-family and multiunit residential buildings alone range from $39 billion to $45 billion. Tax credits for charger installation in the IRA fall far short of this amount, although strong demand for BEVs so far indicates that higher income households are not limited by tax credits. Cost estimates for local and intercity shared charging infrastructure range from $28 billion to $53 billion. The IIJA §11401 and Division J, Title VIII authorization and appropriation of $7.5 billion for intercity and other priority charging is but a fraction of this amount; however, all states have submitted plans to fund charging infrastructure improvements using this program, and the Federal Highway Administration has approved these plans (Joint Office of Energy and Transportation n.d.).

State, utility, and commercial funding sources will likely close some of this gap, with an expanding list of rebates and incentives being offered (AFDC n.d.(a)). Another state funding source is from the Volkswagen diesel emissions violation settlement agreement, which provides $2 billion to states for national ZEV enhancing investments, including charging and purchases of electric vehicles, primarily school buses (NASEO n.d.). Moreover, private sustainable business models for charger installation and operation are beginning to be demonstrated, partly through

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¹⁰ Range estimated from lowest to highest cost scenarios in McKenzie and Nigro (2021) and Phadke et al. (2021).

manufacturer-supported local and intercity networks, such as Tesla’s network of chargers for its vehicle owners (Jockims 2022; Tesla n.d.). Recently, several large automakers have chosen to adopt Tesla’s charging adapter and buy in to its charging network, which is reported to be the most reliable network by consumers (J.D. Power 2023). Public charging infrastructure is limited, but new programs are providing grants to extend charging networks. For example, investor-owned utilities have been approved to invest $3.3 billion as of early 2022 for charging infrastructure, education, and, in limited cases, vehicle purchase (Lepre 2022). Many local jurisdictions are adding chargers in public spaces using public funds. However, PEV owners report experiencing one in five public chargers out of service when they attempt to use them, adding consumer concerns about charger reliability to concerns about overall charger availability (J.D. Power 2023).

Critical Minerals and Materials Supply Barriers

The growth in decarbonization technologies (including batteries, motors, electronics, and other components) is expected to dominate future global needs for various critical materials (including lithium, cobalt, and nickel). All mineral demand for clean energy is expected to increase by 2–6 times by 2040, based on stated national policies (2×) and a global net-zero scenario (6×). The majority of the minerals demand in these scenarios is for EVs and battery electricity storage (IEA 2022b). The growth in demand for energy transition minerals will occur alongside a decrease in extraction of fossil fuels, particularly coal mining. Notably for transportation applications, EVs are more materials-intensive to produce than ICEVs,¹¹ and require larger amounts of critical minerals than ICEVs.

Critical minerals needs for EVs are dominated by the materials required to produce high-capacity batteries, especially for BEVs (IEA 2021b). DOE identified several important materials for the PEV and FCEV industries described in Table 9-3.

The U.S. Geological Survey also produces a list of critical minerals relevant to the entire U.S. economy, which is broader than those required for energy technologies (USGS 2022). The IRA defines critical minerals for EVs to include aluminum, cobalt, graphite (natural and synthetic), lithium, manganese, and nickel.

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¹¹ Although they are more materials-intensive to build, EVs have lower life-cycle energy and GHG emissions than ICEVs. Representative life-cycle GHG emissions from BEVs are significantly less than ICEVs because the total emissions are dominated by the operational phase, where ICEV combustion emissions are very high (EPA n.d.; IEA 2021a).

TABLE 9-3 Important Minerals and Materials for Electric and Other Vehicles as Identified by DOE

SOURCE: DOE (2023a).

Supply of critical materials is important both for automakers’ ability to produce electric and conventional vehicles and also because of the critical minerals sourcing requirements in the IRA. The rapid global increases in EV production and vehicle range are major challenges to production of components for lithium-ion batteries and neodymium iron boron magnets, a key component of highly efficient electric motors. The chemical composition of lithium-ion EV batteries is changing as automakers improve their technologies to reduce cost; improve energy density, charging capability, and range; and reduce supply chain risks. The most common battery type has graphite anodes with nickel-manganese-cobalt cathodes of varying composition. Also common are nickel-cobalt-aluminum batteries. Lithium-iron-phosphate batteries are growing in use, especially in the Chinese market. In the past several years, cobalt use in batteries has dramatically decreased with increased nickel content, and that change in chemistry, along with growth in lithium-iron-phosphate batteries will further reduce supply chain constraints related to critical minerals.

The growth in minerals needs will require increases in production from existing mines and other mineral resources, development of new mines, and development of recycling technologies and facilities. Near-term supplies of minerals are expected to be able to meet demand; however, medium- and longer-term supply chain risks may slow the energy transition as soon as 2030–2035, if current production and investment trends continue (DOE 2023a; IEA 2022b). Current production of many critical minerals is concentrated geographically by location of mineral deposits, and of

production or processing facilities, which is in part associated with the cost of mineral extraction and processing. Some sites of mineral production and processing have low labor and environmental standards and regulations, and so mineral and material production is sometimes associated with child and slave labor as well as environmental destruction, notably cobalt production in the Democratic Republic of the Congo. Companies are under pressure to end sourcing of materials produced under such conditions, which is a major motivator to produce batteries with limited cobalt content, for example. China is a dominant producer and processor of both critical minerals and materials, as well as finished battery components, cells, and packs, and is the largest market for electric vehicles. For example, China produces 60 percent of rare earth elements, and refines approximately 35 percent of nickel, 50–70 percent of lithium and cobalt, and nearly 90 percent of rare earth elements (IEA 2022b). Other major producers of critical minerals and materials include Australia, Chile, the Democratic Republic of the Congo, and Indonesia.

Concern for U.S. economic competitiveness and security in critical mineral and EV battery production led to provisions in the IRA to encourage domestic production and processing of battery minerals, domestic assembly of batteries, and sourcing from countries with free trade agreements with the United States (IEA 2022b). A recent study of the feasibility of the IRA’s critical minerals requirements for EVs found that even with maximum availability of minerals from U.S. or free trade sources on the market value basis required by law, available materials are just shy of the requirements for lithium-iron phosphate and nickel cobalt-aluminum chemistries and reach only one-quarter to one-half of the requirements for nickel-manganese cobalt chemistries (Trost et al. 2023). Development of mines from discovery of a resource to first production takes more than 15 years on average, so in the medium term, there is a risk of critical minerals supply constraining electric vehicle production (IEA 2022b).

The IRA materials sourcing and EV battery assembly requirements also reduce the availability of electric vehicles eligible for tax credits in the near and possibly medium term; however, there are signs that automakers are adjusting their production of both minerals as well as batteries to capture higher tax credit value for their customers (Schwartz 2023). Countries are also considering signing new trade agreements to garner the higher value that their mineral exports would have if eligible to qualify under the IRA requirements, so more qualifying resources may become eligible over time (Bond et al. 2023). Recycling of used batteries and other components is another possible source of critical materials in the future. There is considerable commercial interest and authorized and appropriated funding support from the IIJA for facilities and processes (DOE n.d.(b)).

Supportive Policies

Federal, state, and local governments can help institute regulations, policies, and programs to overcome barriers and promote ZEV purchases toward achieving 2030 sales goals beyond the authorized and appropriated funding provided through the IIJA and IRA. As discussed in Chapter 5, innovative public engagement strategies may also be required to help people navigate the transition to new vehicles and technologies and the adjustments required to expectations and practices. Additionally, private sector actors including fleet owners and operators as well as manufacturers are taking actions that advance decarbonization owing to their own business interests. Some common strategies include

• Federal Vehicle Fuel Economy and Emissions Standards. The National Highway Traffic Safety Administration (NHSTA) and EPA have released new vehicle fuel economy and GHG emissions standards, respectively, under their existing legislative authorities. In April 2023, EPA proposed more stringent, performance-based GHG and criteria pollutant standards under the Clean Air Act for model year 2027–2032 light-, medium-, and heavy-duty vehicles. EPA projected that in model year (MY) 2032, the standards could result in nearly 70 percent BEV sales in the LD fleet, 40 percent in the medium-duty van and pickup fleet, 50 percent ZEV sales in vocational vehicles, 34 percent ZEV sales in day cab tractors, and 25 percent ZEV sales for sleeper cab tractors in MY 2032 (EPA 2023a,b,c,d). Upon a review mandated in Executive Order (EO) 13990, the Department of Transportation (DOT) revised the fuel economy standards for MY 2024–2026, which would result in a fleet-wide average fuel economy of 49 miles per gallon for MY 2026, and, according to DOT projections, yield an 8 percent reduction in CO₂ emissions from passenger cars and light trucks between 2021 and 2100 compared to the alternative of leaving the less stringent Safer Affordable Fuel Efficient Vehicles Rule in place (EO 13990 2021; NHTSA 2022). Under the same regulatory review required by EO 13990, in 2022 EPA restored its waiver of preemption of California’s GHG and ZEV standards, allowing their Advanced Clean Cars (ACC) program to continue as well as allowing other states to adopt the California standards pursuant to Clean Air Act Section 117 (EPA 2022a). In July 2023, NHTSA continued to update its regulations under its existing authority from the Energy Policy and Conservation and Energy Independence and Security Acts, proposing an 18 percent increase in fuel economy from MY 2027–2032, with trucks requiring greater yearly fuel economy increases than cars (NHTSA 2023). The 2021 National Academies’ report on setting national CAFE and GHG standards recommended that federal agencies “use all their delegated authority to drive the development

• and deployment of zero-emission vehicles (ZEVs),” especially EPA’s continued setting of GHG standards based on growing availability of ZEVs and efforts to inform and educate consumers about EV fuel and maintenance cost savings (NASEM 2021b, p. 6).
• State ZEV Purchase Mandates. California ZEV regulation enacted in 2022, known as Advanced Clean Cars II (ACC II), requires 100 percent of LDV sales to be either BEV, FCEV, or PHEV by 2035. More than 40 percent of the LDV market may follow California’s ZEV policy if the 17 states that currently adopt other California emissions standards also adopt the ZEV policy (Tal et al. 2022).¹² As noted earlier, California has added the ACT mandate that would require all new MHD trucks to be ZEVs by 2045. Slowik et al. (2023) estimate that if the 17 states that have previously adopted California’s emissions policies adopt California’s 2035 LDV and 2050 truck ZEV sales share mandates, LD PEV sales share would reach 63 percent and MHD PEV sales share would reach 56 percent by 2035, even with the phaseout of IRA incentives in 2032.
• State Low Carbon Fuel Standards. California includes a low carbon fuel standard (LCFS) as one of the main pillars of its efforts to promote ZEVs (CARB n.d.(b)). Oregon, Washington, and British Columbia have adopted similar standards. LCFSs set a gradually more stringent requirement for fuel providers to reduce the carbon intensity of liquid fuels brought to market. LCFSs do not dictate which fuels or technologies should be adopted; rather, they rely on market mechanisms to achieve a performance standard.
• State Vehicle Purchase and Charger Installation Incentives. As described in the previous section, the IRA has numerous tax credits to enhance supply and demand for PEVs and low carbon liquid fuel production. Several states (e.g., California, Colorado, Pennsylvania, Vermont, and Washington) and the District of Columbia offer additional tax credits or rebates for PEV purchase (AFDC n.d.(a)). Several states also provide tax credits for home charger installation, and/or state regulators allow utilities to provide discounts and charge the cost to their entire rate bases. Additional states could adopt these policies. State incentives for purchase of electric vehicles or charging infrastructure are countered by PEV-specific registration, charging, and other fees being instituted in more than 30 states. In many cases, these fees are described as an attempt to replace the gas tax revenue from BEVs that do not use gasoline; however, they are often set at levels much larger than the equivalent gas tax

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¹² As of June 2023, 12 states have adopted (Maryland, Massachusetts, New York, Oregon, Vermont, Virginia, and Washington), partially adopted (Colorado), or plan to adopt (Delaware, New Jersey, and Rhode Island) ACC II. Six states have adopted California’s previous emissions standards but have not adopted ACC II (Connecticut, Maine, Minnesota, Nevada, New Mexico, and Pennsylvania).

• (Lee and Aton 2023; Preston 2022). The gap in transportation funding from decreasing gas tax revenues is only minorly owing to PEVs because they are a very small portion of the fleet, but will need to be addressed comprehensively at the state and federal levels as PEV deployment becomes widespread (TRB and NRC 2015).
• Improvements in Charging Infrastructure. Building code requirements that include home charging capability in new structures are being enacted by local jurisdictions and some states (Salcido et al. 2021). Standardization of plug-in connectors and open consumer search and reservation capability across charger providers and networks would also be helpful (Alliance for Transportation Electrification n.d.). Provision of charging infrastructure requires the capability of the local electric grid to provide sufficient power (see the section “Actions to Expand the Innovation Toolkit” and Chapter 6), which is something state utility regulators can consider when reviewing utility capital investment plans.
• Innovation for Electric Vehicles. Government support for battery research has been essential to make PEVs commercially competitive (DOE-VTO n.d.). Further areas of government R&D to improve vehicle performance and reduce cost are described in the section “Actions to Expand the Innovation Toolkit.”
• Other Supportive Policies and Actions, Including by Private Sector Actors.
  • Fleet Electrification. Fleet electrification can be a useful additional strategy. Numerous private firms have announced plans to electrify part of their fleets, including Amazon, FedEx, and UPS (Domonosky 2021). Government agencies and nonprofit organizations that own fleets are also beginning to require purchases of electric vehicles, in part for operating cost and emissions reductions, including vehicle fleets from the postal service and the Department of Defense (DoD) (Department of the Army 2022; EO 14057 2021; USPS 2023). DoD and the National Aeronautics and Space Administration have used their procurement power to drive innovation in clean energy technologies, and continue to do so for vehicles (ITIF 2022). While rail transit generally is already electrified, transit and school buses can be electrified, especially as battery range improves and electric bus costs decline (Tong et al. 2017). The IIJA (§11101, §30017, §71101) includes $10 billion in authorization and appropriations for low- or no-emissions transit buses as well as electrification of school buses and associated charging infrastructure. These funds will address only a small share of the existing fleets of buses, but should help motivate a shift in demand, especially if ramping up production to achieve scale economies

• • can reduce initial cost premiums over diesel vehicles. Fleet operators can often centralize necessary charging infrastructure, an area where IRA tax credits and additional discounts provided by utilities could accelerate demand.
  • Business Commitments from Manufacturers and Others. Automakers are committing to produce EVs and other clean vehicles to meet customer demand, lower production costs, comply with regulations in many jurisdictions, meet corporate sustainability commitments, and compete in the global marketplace. In particular, major U.S. and global automaker electrification targets are produced in Table 9-4 (IEA 2023). As noted in IEA (2023), these announced automaker targets are often more ambitious than regulatory requirements or stated government pledges, but are generally non-binding. Some of the most ambitions pledges are for full electrification by 2025–2030, and less ambitious pledges are for a smaller percent of sales, a fixed number of models, or a mix of technologies including non-ZEV technologies.

Many other state and local actions can also boost demand for PEVs (Baldwin et al. 2021). Included among them are giving preferences in road and parking space allocation to PEVs and facilitating zoning and siting of charging infrastructure, including on public property such as municipal parking lots and garages and street parking spaces. Tax credits provided through the IRA and authorized and appropriated funding for chargers provided through the IIJA are market-pull strategies designed to incentivize consumers. Comparable, but limited, state tax credits for vehicle purchases and home charging serve the same function. California’s experience indicates that its ZEV sales mandate, a market-push strategy, is its single most important ZEV policy, but it is complemented by its LCFS and several other state programs (Sperling et al. 2020). Federal fuel economy and GHG emissions standards, although less direct, can also serve to push manufacturers to produce and market PEVs. These market-pull and market-push strategies complement one another and will have even greater influence if the up to 17 states that follow California’s ZEV purchase mandate implement comparable policies (Slowik et al. 2023; Tal et al. 2022).

Electrification of Railroads, Ships, and Aircraft

Electrifying vehicles coupled with net-zero electricity generation is a decarbonization strategy that can be applied to all types of vehicles. However, range, power, and weight issues make battery electric approaches challenging for trains, ships, and aircraft.

TABLE 9-4 Automakers’ Electrification Targets for LDV Since 2022

NOTE: Note that most all-electric automakers such as Tesla are not represented in this table. SOURCE: IEA (2023), https://iea.blob.core.windows.net/assets/dacf14d2-eabc-498a-8263-9f97fd5dc327/GEVO2023.pdf. CC BY 4.0.

Locomotives and Rail Vehicles

Because locomotives and rail vehicles operate on fixed routes with dedicated infrastructure, electric power can be provided to moving vehicles, rather than being stored on the vehicle as for roadway vehicles. Locomotives and rail vehicles can use catenary or third rail for electricity, but the catenary is expensive, vulnerable to failures, and unaesthetic to many. The alternative of third rail power is also expensive, may require power distribution upgrades, and raises safety concerns for maintenance and yard workers and public trespassers across and along rail lines. While catenary and third rail can be used effectively in some situations, they are unlikely to prove practical for all rail lines. One area where electrification may be adopted more quickly is in rail yards, analogous to port operations, where electrification, including electric locomotives, can provide emissions reductions in and near urban areas as well as benefit from easier access to infrastructure and no requirement for long-distance travel.

Battery electric locomotives are now commercially available and are being used in demonstrations (Popovich et al. 2021). Cost, range, and weight limit their widespread adoption. Fuel cells are also feasible, but also currently have significant cost penalties and safety concerns. Until technology and IRA incentives significantly

reduce the cost of fuel cells and low-carbon hydrogen (see the section “Actions to Expand the Innovation Toolkit”), widespread adoption of battery electric or fuel cell locomotives will likely be slow.

Ships

As with locomotives, battery electric and fuel cell ships are available and in use for limited applications. Large marine vessels are good candidates for fuel cells, but cost-effectively producing and providing low-carbon hydrogen or ammonia produced from hydrogen at port locations requires further innovation. Nuclear propulsion is used for submarines and large military vessels but higher cost limits widespread adoption of these alternative propulsion systems. Providing net-zero shore power for ships in port is one strategy that can be cost effective and reduce emissions in urban areas, but requires substantial port investments (EPA 2022b).

Aircraft

Aviation represents 10 percent, and growing, of transportation GHG emissions (EPA 2021; see Figure 9-1). Aircraft, however, require high power and are severely constrained by weight, so the prospect of electrifying air travel with batteries is daunting. Battery electric technologies can be employed for short flights on small aircraft (air taxis) or drones. Operational improvements and aircraft design changes can also provide emissions reductions. For example, airports and passenger and freight airlines could increase use of electric vehicles in multiple airport operations, including to tow aircraft to and from runways rather than aircraft taxiing (NREL 2017). However, the largest improvement will likely be from low-carbon fuels, which will not be available in large volumes for several decades (see the section “Actions to Expand the Innovation Toolkit”). Figure 9-4 shows a possible scenario for reduction of emissions from flights within the United States and international flights by U.S. carriers as developed by the Federal Aviation Administration (FAA n.d.). The history of emissions from passenger and freight aviation operations from 2020–2023 are plotted in white. A future scenario shows the trajectory of emissions from 2019 levels to zero by 2050. Emissions assuming frozen 2019 technology is the base case, and the emissions reductions from various technology, operations, and fuel improvements are shown as different-colored wedges.

In addition to on-road vehicles, other transportation activities may also be usefully electrified, and in some cases are already being electrified, driven by local air quality or cost of ownership considerations. Examples include pipeline processes (e.g., pumping), port operations including drayage vehicles, and off-road vehicles.

Findings and Recommendations

GHG REDUCTION THROUGH TRANSPORT EFFICIENCY

Improving the efficiency of energy used to provide transportation of goods and people generally results in lower impacts from transportation systems, including fewer GHG emissions. A wide range of measures to improve travel efficiency can reduce transport GHG emissions. Although these efficiency improvements would make only modest contributions to reaching 2030 and 2050 decarbonization goals, they could have co-benefits such as reducing travel costs and increasing overall economic efficiency.

Internal Combustion Engine Vehicle Efficiency Improvements

Fuel economy of LD ICE vehicles has improved significantly over the past 50 years. This efficiency improvement resulted in a drop in total fuel use from 2005 to 2020 even though number of vehicle registrations increased (NASEM 2021b) (Figure 9-5). Regulatory requirements such as the federal CAFE standards for passenger vehicles and

trucks, which was established in 1975 and has tightened over time, have provided a major incentive for this efficiency improvement and will remain important because of the tens of millions of fossil fuel vehicles that are likely to continue to be in operation for decades to come. Numerous technical means to improve fuel economy exist, so efficiency improvements are likely to continue in the next few decades. For example, vehicle lightweighting can dramatically improve energy efficiency for either ICEs or EVs (Lovins 2020). Fuel economy regulations require consideration of not only technical opportunities but also their costs and benefits to the consumer, manufacturers, and the economy as a whole, including aspects such as safety¹³ and national energy security.

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¹³ Various factors affect vehicle safety, including factors associated with the driver, transportation system, and vehicles. Implications of fuel economy regulations have been small, relative to primary determinants of vehicle safety; however, they are important to understand and address. The National Academies’ Committee on Assessment of Technologies for Improving Fuel Economy of Light-Duty Vehicles—Phase 3 examined the implications of a future mixed fleet with various technologies, especially a mix of different vehicle weights, sizes (especially a shift from sedans to crossovers, SUVs, and trucks), and safety technologies, and recommended that NHTSA study potential changes in mass disparity and societal safety risk (NASEM 2021b).

For MHD roadway vehicles, regulation of fuel economy has only occurred over the past 10 years (NASEM 2020). As a result, fuel use efficiency improvements in this transport subsector have been scant. Over the next 2 decades, only a 13 percent improvement (from 6.9 miles per gallon to 7.8 miles per gallon) is anticipated for freight trucks. As a result, other means to reduce GHG emissions are priorities for these vehicles, such as alternative fuels or freight system improvements, as discussed below.

Airplanes, locomotives, and ships also present opportunities for fuel efficiency improvements (Lovins 2021). For example, from 1960 to 2020, revenue passenger kilometers per kilogram of CO₂ emitted from airplanes grew eightfold (Lee et al. 2021). Although these transport sectors have strong economic incentives to reduce fuel consumption, there are no regulatory requirements for fuel economy applied to them. As discussed previously, alternative fuels or electrification, where possible, are primary means to achieve net-zero vehicle movements for airplanes, locomotives, and ships. Development of sustainable alternative fuels for these sources—which represent 14 percent of transportation GHG emissions (see Figure 9-1)—is a high priority of innovation and federal and private RD&D.

Traffic Flow Improvements

Improving efficiency with better traffic flow management is a widely held goal for agencies and firms. Operational improvements are also being pursued, such as adaptive traffic signal systems or optimized airplane routing and operations. Tracking vehicle locations and using vehicle connectivity aid these operational strategies. Avoiding vehicle crashes can also improve traffic flow by avoiding the congestion resulting from incidents. Partial vehicle automation, including positive train control for freight and passenger rail, and active roadway vehicle braking can help avoid such crashes.

Road traffic flow management improvements will typically not be the result of federal actions, as there is no current federal role in managing on-road traffic, unlike air traffic, which is a fully federal responsibility. Urban roadway networks are a state and local responsibility. Rail networks are managed and owned by private corporations for the most part, except for Amtrak’s ownership of the Northeast Corridor rail lines and state ownership of limited other mileage used for passenger rail. The federal government can help by funding research on improvements and participating in standard setting.

As travel demand grows, the GHG emissions reduction potential of improved traffic flow management will erode. In essence, greater traffic volumes without infrastructure capacity expansions will reduce the efficiency of traffic flow owing to congestion (NASEM 2019d). While improved traffic flow management may reduce

congestion and avoid bottlenecks, it likely will not achieve significant GHG emissions reductions. Even so, it can mitigate GHG emission increases from ICEVs during the decades in which they will continue to operate, and pricing lane additions through electronic tolls that vary with demand can mitigate induced travel (Milam et al. 2017, p. 14).

Rail and Marine Freight Efficiency Improvements

While non-truck freight movements are only a fraction of overall transport GHG emissions, there is potential for efficiency improvements in other modes, including rail and marine. Freight railroads have made considerable reductions in fuel expended per ton-mile in the past decades by rebuilding their tracks, carrying heavier weights, pulling more cars, and more carefully managing speed and acceleration. Large ships have also reduced fuel per ton-mile, largely through scale economies associated with larger container ships. However, infrastructure constraints limit the amount of further improvement achievable in a cost-effective fashion. For example, double tracking railroads would improve movement efficiency, but obtaining the required rights-of-way is difficult and raising bridges is expensive. Nevertheless, infrastructure investments to remove major freight bottlenecks can be pursued for situations such as congested land-side access to ports and heavily congested interstate highway interchanges.

Modal shifts in freight transportation offer another means to improve efficiency. While routing on rail or inland waterways may be longer in both distance and time, and short-sea shipping along coastal routes has so far failed to gain substantial market share in the United States, these modes have lower fuel use and GHG emissions per ton-mile of freight movement (Corbett et al. 2008). Shifting freight from trucks to rail or water for long-distance movements can reduce overall GHG emissions. The carbon tax endorsed in the committee’s first report and in Recommendation 1-1 of this report, or increased federal and state motor fuels taxes on trucks, would encourage such mode shifting. Efficiencies may also be achieved through information technology. Delivery loads and routes can be optimized. Greater consolidation of freight to fill combination truck trailers (within size and weight limits) can improve efficiency.

Freight transport efficiency can help reduce GHG emissions and reduce overall costs. For example, data sharing, communication, and more efficient routing of vehicles, both within fleets and also among all vehicles, ports, and other origins and destinations can reduce congestion, wait times, and emissions. While GHG emission

reductions for modes other than trucks will be modest, the improvements can be cost effective, and may be important for modes like marine freight in reducing port congestion and associated emissions.

Automation and Connectivity

Vehicle automation and connectivity is already appearing in new vehicles to some extent. Partial automation and driver warning systems have reduced the numbers of collisions (Flannagan and Leslie 2020). Adaptive cruise control has improved fuel efficiency with smoother driving. Highly automated vehicles could have greater savings, including aerodynamic savings from truck platooning. Safer automated vehicles might also be smaller and lighter than vehicles in a comparable non-automated fleet. Depending on public policies, in a scenario with greater automation, travel demand may increase owing to traveler shifts from transit into automated vehicles, and automated vehicle trips without passengers. Automation and connectivity can increase or decrease energy efficiency of vehicle operation in both scenarios with limited automation as well as scenarios with nearly full penetration of highly automated vehicles (NASEM 2021b). Changes to vehicle ownership models and increased vehicle electrification to facilitate automation may add to the complexity of predicting efficiency outcomes.

Information and Communications Technology Substitutes for Transport

In many cases, information and communications technologies (ICT) can substitute for travel and thus reduce GHG emissions. Telework can reduce or eliminate commuting travel for those workers able to use this option. E-commerce can replace some consumer shopping trips (Matthews et al. 2001). Video conferencing can reduce some travel for meetings, including long-distance trips by air. School and medical trips can be reduced through online learning and virtual visits with medical practitioners, respectively. Of course, these substitutions often result in only a partial reduction of motor vehicle trips and travel and will not always replace the quality of in-person interactions. For example, teleworkers generally travel more overall than workers who do not telecommute (Speroni and Taylor 2023). E-commerce purchases increase delivery vehicle travel while also reducing personal vehicle shopping trips (Matthews et al. 2001). Most advantageous in reducing GHG emissions is use of enhanced videoconferencing technologies that became available during the COVID-19 pandemic to substitute for energy-intensive trips by aircraft. A variety of federal, state, and local policies can affect ICT travel substitution. For example, public support for Internet access in rural and less-developed urban areas would support wider use of ICT and provide equity benefits.

Biking, Shared Rides, Transit, and Walking Coupled with Development Density

Reducing single-person trips in LDVs by shifting to bicycling, shared rides, transit, or walking can reduce vehicle miles traveled and vehicle emissions. Biking and walking also offer the advantage of healthy exercise, as discussed in Chapter 3 (Public Health).¹⁴ The impact of biking, walking, and transit on transportation GHG emissions, especially in the near term, is limited by the nature of transportation needs in the United States today, which are themselves heavily influenced by land use patterns. Trips tend to be relatively long, and thus accomplished by personal vehicles, which therefore results in the majority of emissions. The majority of annual average person trips (about 83 percent) is in personal motor vehicles, with walking at about 10 percent, public transit at about 2.5 percent, and biking at about 1 percent (ORNL 2017). Passenger miles of travel are the more important comparison for GHG emissions, and are even more skewed toward personal motor vehicles. Passenger miles (excluding aviation and intercity rail) are dominated by personal motor vehicles (86 percent), with public transit at 1 percent, walking at 0.6 percent, and biking at 0.15 percent (BTS 2021b). A variety of policies can affect these modal shares somewhat, such as increasing transit service frequency or providing dedicated bike lanes and sidewalks (NASEM 2021e), but it would take very large shifts away from personal motor vehicles to significantly reduce total passenger GHG emissions. For example, doubling walking, biking, and transit trips, and assuming that this doubling replaced trips by personal motor vehicles, would reduce personal motor vehicle miles of travel from 86 to 82.5 percent, and the GHG emission benefits would be lessened to the extent that substituted trips were made in PEVs.

Changes to denser, mixed-use, and active-transportation friendly land use patterns could also reduce transportation GHGs, but on a smaller scale and more slowly than policies aimed at electrifying vehicles. Making communities more walkable and bikeable through density increases, mixed-use development, and improving transit service could reduce the reliance on personal vehicle travel, and serve important public health and equity policy goals (DOT 2022). Such policies are being actively pursued in many communities; however, fragmented regional governance of land use, entrenched zoning policies, and public preferences that determine residential and commercial development patterns can be slow to change (Cervero 2003; Savitch and Adhikari 2017; Schuetz 2022).¹⁵ Also, the turnover of the LDV

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¹⁴ Cycling, like other transportation modes, has applications where it is more or less effective and accessible. Cycling tends to be seasonal, limited by topography, and not equally accessible across age and ability groups. Electric assisted bicycles are a growing aspect of cycling for transportation that can better serve different ages, ability groups, and types of trips.

¹⁵ See also A. Downs, 1992, Stuck in Traffic, Brookings, https://www.brookings.edu/book/stuck-in-traffic, and A. Downs, 2004, Still Stuck in Traffic, Brookings, https://www.brookings.edu/book/still-stuck-in-traffic.

fleet is inherently faster, on the order of 1–2 decades, relative to land development, which, during periods of slow economic and population growth, turns over on the timescale of a century or more.

State policies can have an influence on development patterns. States have the power under their constitutions to override local autonomy on zoning and land use, but doing so to increase density has been rare to date. As important exceptions, Oregon (2019) and California (2021) passed state laws that would override local zoning restrictions on density increases that prohibit conversion of single-family lots to duplexes, and up to quadruplexes in limited cases (California City News 2021; Shumway 2021). However, density increases that double the density of single-family residential development, and assuming mixed-use zoning to reduce motor vehicle trips, would likely have modest impacts on reducing auto trips (TRB 2009). Although increases in residential density have been accepted in cities such as Portland, Oregon, and are promoted by the “yes in my backyard” movement, strong resistance to changes in residential zoning has a long history in the United States (Downs 1992, 2004).

California has gone further to comprehensively address housing availability and affordability. In 2022, the state enacted a bevy of new and modified laws to streamline permitting, increase development density, restrict parking, and other measures that could have greater impact on motor vehicle trips (Maclean et al. 2022). To reach California’s goal to fully decarbonize transportation by 2045, Brown et al. (2021) assumed that 15 percent of California’s transport GHG reduction could be achieved by reducing per-capita vehicle miles traveled through pricing roads and parking (−5.5 percent); Transit Oriented Development, Active Transportation, and Transit (−4.7 percent); telework (−2.5 percent); and other strategies (−2.3 percent).

Transport Infrastructure Construction and Maintenance

Relative to direct vehicle emissions, the GHG emissions from infrastructure construction and maintenance are relatively modest but still important. For example, including them would result in a roughly 10 percent increase over passenger vehicle emissions in the case of highways (Chester and Horvath 2009). Emissions from infrastructure are associated with purchases of carbon-intensive materials such as cement. The largest supply chain inputs into new highways, bridges, and other horizontal construction are engineering services, wholesale trade, trucking, concrete, asphalt, stone, concrete products, asphalt felts, petroleum, steel, and fabricated metal (Hendrickson and Horvath 2000). A variety of approaches can be used to reduce emissions from these inputs. Reducing direct emissions from carbon intensive inputs can be a very effective approach. Cement and steel production can use innovative processes to reduce GHG

emissions in their production, as discussed in Chapter 10 (Industrial Decarbonization). Vehicles used for construction and maintenance can be electrified.

The IRA includes several new programs to help speed decarbonization of infrastructure materials (Margolies 2022). Industries can apply for grants from the $5.8 billion Advanced Industrial Facilities Deployment Program (§50161) as well as receive tax credits to speed decarbonization (§13502). The IRA included $4.5 billion for federal procurement of low-carbon materials for projects (§60116, §60502, §60503, §60506) and designated another $250 million to aid in producing Environmental Product Declarations that document carbon intensity of materials (§60112).

Infrastructure design, construction, and maintenance processes also provide opportunities for GHG emission reductions (Rangelov et al. 2022; Santero et al. 2011). For design, material use can be reduced, or less GHG intensive materials employed. For example, scrap tire material and asphalt shingles are used in pavements to reduce the need to produce new materials (TRB 2013), and asphalt is commonly recycled in repaving projects. For construction, GHG emissions may be reduced through procurement, contracting, and operational changes such as work zone controls (NASEM 2019e). Maintenance equipment and vehicles can be electrified. Standards and best practice guides can be formulated at the federal or state levels for such changes.

Findings and Recommendations

EQUITY AND OTHER CROSSCUTTING ISSUES

Energy and Climate Justice and Equity

For decades, transportation policies have focused on technical aspects such as optimizing the performance and efficiency of the transport system. This focus has had broad economic benefits but has also imposed deep inequities. Some U.S. populations have enjoyed the fruits of the improving system, while others—such as low-income

and rural populations and people of color—have experienced fewer benefits, greater economic burdens, and increased health risks from exposure to vehicle emissions and noise (Chapter 3). Racially segregated neighborhoods, attributable to a history of housing discrimination and redlining, are disproportionately located in central cities with poorer access to employment and amenities (Blumenberg 2017). They have also had their communities divided or destroyed by transportation infrastructure (Martens 2016; NASEM 2021e). Electrification of transportation vehicles will provide substantial benefits to low- and moderate-income residents living near transportation infrastructure and ports by reducing vehicle emissions harmful to public health. Although they will benefit from lower emissions exposures, without additional policies and programs, the initial growth in EVs will have limited benefits for the lower-income drivers or owners of vehicles who will find it hard to purchase a new EV, nor will EV growth result in expanded mobility options for those who cannot afford to own vehicles. As discussed in the section “2030 ZEV Sales Goals and Barriers,” the IRA includes specific efforts to make PEVs and charging accessible to low-income households, but broad penetration of PEV ownership in this income group will require additional efforts.

Although roughly 20 percent of low-income households depend on public transportation to reach jobs and other destinations, about 80 percent live in households with a least one vehicle and rely on vehicle sharing and other LDV strategies for access to employment and amenities (Blumenberg 2017; Figure 13-2). Despite the considerable variation in employment accessibility across metro areas, households with automobiles have access to far more jobs than transit-dependent households, as well as higher earnings and job tenure (Smart and Klein 2020). Moreover, as jobs and poverty have increasingly suburbanized over time, and given the difficulty fixed-route transit has in serving suburban and exurban geographies, automobile access has joined transit service to low-income communities as an equally important equity issue (Romero-Lankao et al. 2022). As the personal vehicle fleet shifts to PEVs, equitable access to these vehicles will also loom large.

Equity Policies and Programs

Equity policies and programs can improve access to mobility for underserved populations as the transportation system decarbonizes. As noted above, 20 percent of low-income households depend on public transit. Transit service to low-income, transit-dependent populations is provided across the country by thousands of transit agencies, but service is typically limited and infrequent outside of a few transit-rich urbanized areas. Funding could be supplemented for this purpose and could be drawn from sources that also serve to reduce ICEV demand, such as carbon taxes, congestion fees, or highway tolls imposed to manage auto demand. Access to transit

could be expanded through subsidies for car-, bike-, and scooter-sharing services in low-income areas (NASEM 2021e).

The IRA and the IIJA include important equity-enhancing policies to make LD PEVs more affordable to low- and moderate-income households. Up until 2020 or so, relatively few EVs had filtered outside of higher-income areas (Tal et al. 2021). The IRA for the first time includes a federal tax credit for the purchase of used EVs with a price cap of $25,000 (§13402). Used cars represent the major source (66 percent) of vehicle purchases for low-income households (Board of Governors of the Federal Reserve System 2016). The IRA (§13401) also sets price limits for new EVs to qualify for federal tax credits for sedans ($55,000) and SUVs, pickups, and vans ($80,000), which will encourage manufacturers to offer PEVs at a wider range of price points than their recent emphasis on luxury models (Hardman et al. 2021). Moreover, beginning in 2024, the IRA allows consumers to transfer their tax credit to auto dealers, who would then provide buyers with an equal price discount, which would not require buyers to wait for a tax return for reimbursement, nor require them to have tax liability. This should encourage purchase of PEVs by some low- and moderate-income households. Although new PEVs and new cars generally are still beyond the reach of most low- and moderate-income households, EVs at the price ceilings set in the IRA for tax credit eligibility will begin filtering into the used car market within a few years of sale. Moreover, several compact sedans priced well below these ceilings are being introduced by OEMs. The tax credits available in the IRA for home and commercial installation of charging infrastructure target rural and low-income census tracts, which will facilitate access to public charging by low-income households and renters less able to charge at home.

Enhancing clean automobile access for low-income households could also be pursued through programs such as those that CARB offers for low-income households to purchase ZEV vehicles: scrappage of older vehicles for $9,500; cash assistance of up to $7,000 for qualified households to buy or lease a ZEV; and special financing assistance of up to $5,000 for ZEV vehicle down payments (CARB 2022b). CARB is also pioneering subsidized carsharing and ridesharing programs for low-income households (CARB n.d.(a)). The expanding supply of used PEVs will make them more affordable through cost reductions and as the secondary market develops. Local programs to increase access to used vehicles and to provide counsel on vehicle and insurance decisions and avoiding predatory lending practices would be particularly helpful for first-time, low-income vehicle purchasers (Pendall et al. 2016). Used PEVs entail other issues, such as the risk of owning PEV batteries beyond warranty and accessibility of affordable charging (Hardman et al. 2021). Expanded battery warranty programs and equitable distribution of recharging infrastructure supported with public funds would

help address these issues. States and local governments can learn from the many aforementioned policies and programs that are being experimented with and implemented in California.

Workforce Needs, Opportunity, and Support for Transportation Decarbonization

Transitioning from ICEVs to PEVs will have broad positive consequences for society and consumers, but some transport sector workers will face diminished employment opportunities as a result of EVs that are simpler to produce and maintain than ICEVs. For example, a recent set of decarbonization scenarios finds net increases in employment across the economy but declines in fossil fuel and transportation employment by 2035 (WRI 2022). In these WRI projections, most of the transportation employment decline is owing to reduced ICEV manufacturing employment (a loss of about 5.5 million jobs in the net-zero scenario), whereas employment growth in manufacturing for PEVs and in charging infrastructure would fall 2 million jobs short of replacing these losses. PEVs, having more integrated designs with fewer parts, can be produced with fewer workers per unit of output than ICEVs, and new factories are expected to be more reliant on automation than existing ones.

Domestic semiconductor and battery manufacturing and mining may be stimulated by the Creating Helpful Incentives for Producing Semiconductors and Science (CHIPS and Science) Act and the IRA. For example, the North American assembly and minerals sourcing requirements of the IRA will provide new domestic demand for vehicle battery suppliers and their employment needs. The WRI scenarios do not account for local repair and maintenance shops, which are expected to have reduced demand in the future because PEVs have fewer moving parts and electric motors are more reliable than internal combustion engines. CARB estimates that its new LD ZEV mandate (100 percent PEV and FCEV new sales by 2035) will reduce auto repair and maintenance jobs in the state by 13.8 percent (CARB 2022a). If that same percentage is applied to the current U.S. auto repair and maintenance workforce (BLS 2022), it implies a loss of roughly 127,000 jobs, although this reduction would occur slowly over the next 3 decades owing to the very large and slowly declining stock of ICEVs. Recommendations addressing any future employment losses appear in Chapter 4.

Engaging the Public in the Transportation Decarbonization Transition

Special efforts are needed to involve low-income and rural populations in transportation infrastructure planning and decision-making and in researching, developing, and implementing more effective ways of doing so (NASEM 2021d). For more than

3 decades, public participation has been mandated for federally funded transportation projects (NASEM 2019c). Title VI of the Civil Rights Act of 1964 and the Americans with Disabilities Act of 1990 formed the foundations of this requirement. The electric vehicle charging grants authorized by the IIJA require public participation and include 50 percent of funds set aside for community grants that prioritize projects for rural areas, low- and moderate-income neighborhoods, and communities with a low ratio of private parking spaces.

Requirements for public participation in transportation planning in the past, however, have not proven effective in participants’ perceptions of being heard, improvement in the decisions made, or inclusiveness of the full spectrum of the public (Innes and Booher 2004). More meaningful processes require active participation of adversely affected or underserved communities in defining goals, resource allocation, and metrics by which to measure progress (Karner and Marcantonio 2018). In addition to improving opportunities for more meaningful participation, a useful step would be to expand the representation of discriminated-against, low-income communities on the planning, zoning, and transportation agency decision-making boards that plan and provide for transportation infrastructure and services.

Certain transportation-related technologies implemented for decarbonization will introduce new or heightened interest and concern from the public and require special consideration for public engagement. Carbon capture and sequestration, net-zero GHG emissions synthetic fuels, and other carbon management strategies may require investment in new or modified pipelines to transport carbon dioxide or ammonia (Larson et al. 2021; NASEM 2019b). Permitting new pipelines is a lengthy process requiring considerable government and public participation. Thus, making decisions on such pipelines is a priority for net-zero emissions planning, as is ensuring meaningful participation in siting decisions by the public and low-income and minority communities in particular.¹⁶Chapters 2 and 12 discuss pipeline challenges and needs in greater depth.

Health and Environmental Justice in Transportation

The transport sector is the second largest source of U.S. air pollution illness and death next to electric power (Chapter 3). Roughly 20,000 premature deaths in 2017 were attributed to ICEV emissions, with roughly one-third of those deaths resulting from

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¹⁶ Construction and design of new or modified pipelines provides an opportunity to reduce GHG emissions from these processes. For example, recycled materials and electrified construction equipment could be employed.

heavy-truck emissions (Choma et al. 2021). Transport pollutants disproportionately harm low-income and historically marginalized people, primarily in urban areas (Chapter 2). Although net-zero biofuels or synfuels could be employed to eliminate some or all transport-related GHG emissions, they would still emit conventional pollutants at approximately the same levels per distance traveled as fossil fuels. The need to dramatically reduce health impacts of fuel combustion is one of the reasons why combustion of net-zero liquid fuels is expected be a limited solution for transportation decarbonization. More details on the health impacts of transportation decarbonization are found in Chapter 3.

Clean Electricity for Transportation Electrification

Vehicle electrification will result in greater demands on the power grid, in aggregate power demand, and potentially in peak hour demands. For example, California’s overall power demand would increase 5 percent with 50 percent penetration of electric vehicles by 2030, but peak hour demand could increase up to 25 percent with uncontrolled charging times (Powell et al. 2022). Achieving the committee’s 2050 ZEV sales could increase average demand on the electric grid by as much as 28 percent (Oke et al. 2022). The power demands from intercity charging at large passenger/truck stops could reach the magnitude of demand of a small town (approximately 20 MW) by 2035 (National Grid et al. 2022). A variety of strategies can be employed to reduce peak demand by 2030, including local charging from solar panels, switching to off-peak charging (often at the workplace), smart charging systems responding to off-peak tariffs, or even two-way power flows with electric vehicles discharging at peak hours. The overall impact of EV charging on the grid is analogous to the introduction of widespread air conditioning (NASEM 2021c), but there is more opportunity to manage charging demand on the grid from PEVs.

Transportation Fuel Impact on Agriculture, Forestry, and Nature-Based Solutions

Even if the committee’s ZEV sales goals are reached, there will still be substantial demand for low-carbon fuels for industrial heat, aviation, marine shipping, and perhaps heavy road transport. Some of this demand could be met by expanded production of biofuels, but all available land is already claimed for food, wood, and fiber production; biodiversity preservation, land carbon sinks; human settlements, or current biofuels production (16 million hectares, Chapter 8). Constraints are likely to limit carbohydrate

biofuels use to aviation and other applications without likely alternatives. Hydrogen is another alternative to use of biofuels. By midcentury, bioenergy with carbon capture and storage hydrogen may compete with carbohydrate liquid biofuels because this process also produces a sizable and much-needed negative emission (Larson et al. 2021). Heavy trucking and trains may ultimately have an economic hydrogen fueling option, while marine shipping might be economically powered by ammonia produced with low-carbon hydrogen. The IRA provides substantial incentives for biofuels (reviewed in Chapter 8). The largest of these (§13203) appropriately targets aviation (up to $1.75/gallon), but the other major program offers a $1 per gallon tax credit for any second-generation biofuel (§13202).

Findings and Recommendations

ACTIONS TO EXPAND THE INNOVATION TOOLKIT

Although EVs and other transportation decarbonization technologies are commercially available, others are still in research and demonstration status. Even those that are commercially available would benefit from continued innovation to reduce costs and improve effectiveness. Investment in innovation is essential to aid the process of deep decarbonization in transportation. As with all innovation processes, the technical and market successes of developing technologies are uncertain. For example, it is unclear whether FCEVs can be cost-competitive in the marketplace, as discussed below (NASEM 2021b). Pursuing innovation requires flexibility as results are obtained or conditions change. In this section, some priorities for innovation investment are outlined, but innovation investment should shift as results accrue.

Innovation investments can be made by a wide range of individuals and entities. The IRA and IIJA authorize and appropriate substantial RD&D funding to advance decarbonization goals. State governments also play a role, such as the long-standing RD&D support for ZEVs including fuel cell development by the State of California (McConnell et al. 2019). Private companies often pioneer innovation, such as ride-hailing companies, micro-mobility (bike and scooter sharing), and mobility as a service (NASEM 2021e). University research programs such as the DOT-supported university transportation centers often partner with local and state agencies or private firms to research and deploy innovations (NASEM 2019f). Innovation investment is also global in nature, with many innovations pioneered outside of the United States. Motor vehicle manufacturers are a good example of global entities in which designs and technologies are developed for new vehicles sold around the world.

Additional Innovation for Electrification

The EVs available today are the result of focused, long-term investments in basic and applied R&D over decades by automakers, suppliers, and federal and state governments. New motor, power electronics, and battery technologies; manufacturing process improvements, design innovations; and other R&D investments have all contributed to improved power density, reduced costs, and improved range for BEVs and other types of EVs. Further innovation is needed in these areas to continue these trends and increase the attractiveness of BEVs in the marketplace.

As BEVs become more prevalent in the marketplace, other enabling or supporting technologies need innovation investment. Ensuring adequate supply of mineral resources for batteries and electric motors is a concern, as well as developing batteries less reliant on minerals such as cobalt. Recycling processes for batteries and BEVs will be needed, building on the extensive recycling infrastructure for conventional vehicles. End-of-life recycling of electric vehicles and batteries is in its infancy (Chokshi and Browning 2022) and needs innovation. Innovations in support for EV supply chains, especially for domestic manufacturers, are critical to address minerals sourcing constraints imposed by the IRA and reduce costs. Improved recycling and increased recovery of critical minerals and materials requires design of the battery materials, cells, modules, and packs that considers ease of end-of-life recycling and recovery, in addition to R&D of improved processes and systems for battery recycling. Also related to BEV, and particularly battery technology: first responders to crashes (and battery fires) and vehicle mechanics need training to deal with BEVs.

Charging technology, operation practices, and infrastructure for BEVs also need innovation investment, including for shared and wireless charging. Currently, several different types of connector plugs are used for charging, reflecting different choices and proprietary incentives. Standardization of connector plugs has significant benefits for BEV users. Provisions in the IIJA will encourage this standardization because any recharging infrastructure funded through this program will have to be interoperable across proprietary designs. Automakers have recently been partnering to develop or adopt new standards, including several major automakers buying into the Tesla network and standard. Operating procedures for sharing chargers could also be improved, such as across real-time reservation systems and open standards that facilitate this process. Facilitating “smart” charging to optimize the charging cycles, time-shift electricity demand to periods of excess supply (and low prices), and avoid peak electricity demand periods would be beneficial. The IIJA provides substantial R&D funding for DOE to advance technologies for these purposes. Further innovation in bidirectional charging systems can aid resiliency by providing emergency power supply when the grid is unavailable, as already demonstrated commercially by the Ford F-150 BEV (Zhou et al. 2021).

Developing appropriate incentives for using PEVs and discouraging petroleum-based vehicles also require public funding and policies. Much can be learned from other countries taking different approaches to promoting PEVs and doing so equitably.

Although hydrogen fuel cells are a proven technology and in limited commercial use in FCEVs, they currently require a significant capital premium relative to BEVs as well as development of a low-carbon hydrogen supply infrastructure (NASEM 2020). FCEVs generally have the advantage of faster refueling time and longer range, so they could be most competitive for long-distance trucking and potentially for locomotives and ships. Innovations to reduce the cost of fuel cells, improve durability, ensure safety, and improve supplies of low-carbon hydrogen could make the technology competitive (NASEM 2021b). The alternative fuel subsidies in the IRA may accelerate the latter. Innovation for fuel cells might focus on cost reductions and safety assurance (NASEM 2021b), as well as innovations in how hydrogen can be distributed to points of demand in a cost-competitive way.

Other important areas of innovation, as described next, include development at scale of net-zero-carbon liquid and gaseous fuels to provide further options to decarbonize heavy-duty, long-distance road transport, aviation, and shipping and in estimating and verifying the carbon intensities of these fuels on a full life-cycle basis (NASEM 2022a,b).

Innovation in Net-Zero-Carbon Liquid Fuels

Assuming that the committee’s 2030 and 2050 ZEV sales goals are met for LDVs, gasoline consumption by LDVs could be reduced by 80 percent in 2050 in line with the reduction in LDV stock. However, as noted earlier (see Figure 9-3), conversion of ICEVs to EVs may languish and thereby require provision of liquid fuels for decades to come. In this case, some use of biofuels in land transport may need to continue, which supports continued investment in biofuels R&D. Synthetic low-carbon liquid fuels could also be commercially available by 2050. For the hard-to-electrify transportation applications, especially aviation, true net-zero-carbon liquid fuels, with energy density comparable to current fossil fuels, provide the most likely option for decarbonization despite their harmful emissions of conventional pollutants. Such fuels are hydrocarbons where the carbon source and all other inputs result in zero net emissions of GHGs to the atmosphere on a life-cycle basis. Net-zero-carbon fuels can be developed from a variety of carbon sources, such as biomass, recycled carbon-based materials, and carbon dioxide captured from emissions sources or the atmosphere, and net-zero emitting inputs like clean hydrogen and electricity from renewables (Figure 9-6). Net-zero fuel composition may be tailored for standard operation in existing vehicles with no modification of the vehicle required, or for improved operation with optimized vehicle-fuel combinations.

Biomass such as corn, agricultural wastes, or algae could be used as a carbon source for net-zero-carbon liquid fuels, within the limits imposed by land constraints described in Chapter 8, but all GHG emissions with all aspects of fuel recovery and use would need to be eliminated or balanced by negative emissions such as carbon capture and sequestration. Areas of research for other biomass-based fuel processes include biomass-to-gasoline, involving the gasification of biomass and subsequent chemical conversion to fuel, and thermochemical conversion of biomass via pyrolysis or hydrothermal liquefaction followed by chemical refining steps (Phillips et al. 2011; Royal Society 2019).

Captured carbon dioxide is an alternative carbon source for synthesizing net-zero-carbon liquid fuels; however, at present there are no large-scale, low-carbon synthetic fuels available for LDV transportation. Existing gas-to-liquid processes like Fischer–Tropsch synthesis, methanol synthesis, and the methanol-to-gasoline process could be modified to utilize non-fossil carbon and low-carbon hydrogen, or direct chemical conversion of CO₂ may develop, as it is being explored at fundamental research and benchtop-proof-of-concept stages (Basic Energy Sciences Roundtable 2019; NASEM 2019a, 2022a).

Production of low-carbon synthetic fuels is currently limited by high costs and inefficiencies (Cai et al. 2018; Li et al. 2016; Royal Society 2019). High costs and inefficiencies may be acceptable for low-volume, high-value commodities, but they are untenable for very high volume, low-margin products like mass market motor fuels, especially in comparison to inexpensive and readily available gasoline, diesel, and electricity. There are more near-term options for commercial drop-in, diesel-like fuels, as compared to lighter, gasoline-like spark-ignition engine fuels (AFDC n.d.(b)). Net-zero carbon synthetic and biofuels will likely be first introduced as blends with existing fossil fuels (Farrell et al. 2018). Examples of this are already available for diesel blends (Neste 2016; Renewable Energy Group 2020). Low- and net-zero-carbon liquid fuels require robust life-cycle analysis methods to be incorporated into transportation decarbonization policy (NASEM 2022b).

In summary, there are a variety of R&D and innovation investments that need to be undertaken to improve deep decarbonization processes for transportation, especially for hard to electrify transportation modes, and to improve electrification for the majority of vehicles.

Findings and Recommendations

Table 9-5 summarizes all of the recommendations in this chapter regarding decarbonizing the transportation system.

SUMMARY OF RECOMMENDATIONS ON TRANSPORT

TABLE 9-5 Summary of Recommendations on Transport

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