2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Energy Economics Available online 8 May 2023, 106710 In Press, Journal Pre-proof What’s this? ↗ Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model Yongxia Cai a Michael Shelby , Jared Woollacott a , Robert H. Beach a , Lauren E. Rafelski b , Christopher Ramig b , b Show more Outline Share Cite https://doi.org/10.1016/j.eneco.2023.106710 ↗ Get rights and content ↗ Highlights • Transportation detail in economy-wide models significantly alters simulated outcomes. • Electric vehicle (EV) adoption is sensitive to oil price modeling simulations. • EV adoption may reduce greenhouse gas (GHG) emissions, particularly with grid decarbonization. Abstract Computable general equilibrium (CGE) models provide valuable insights into economy-wide impacts of anticipated future structural changes in the transportation sector, yet few CGE models offer detailed transportation representations. We use an enhanced Applied Dynamic Analysis of the Global Economy (ADAGE) CGE model to incorporate disaggregated transportation modes and technologies in on-road passenger and freight transportation. We assess the impacts of these inclusions on U.S. transportation patterns, energy consumption and greenhouse gas emissions. Simulating illustrative global oil price cases with and without transportation detail, we find subsector mode disaggregation and technology additions in a CGE model significantly alter the impacts of oil prices on global trade and freight patterns, energy consumption, and greenhouse gas (GHG) emissions. We find that: (1) alternative technologies are essential for capturing transportation sector impacts, (2) electrification may reduce emissions with electricity decarbonization, and (3) higher oil prices may hasten electrification. Keywords Alternative-fuel vehicles; Economic modeling; Oil price; Transportation policy https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 1/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect 1. Introduction Transportation is an important sector for global economic modeling of energy systems, accounting for 29% of global final energy consumption in 2018 (International Energy Agency, 2020). However, this sector has generally received less attention in economy-wide models than some other major parts of the energy system, particularly the electricity sector (Babatunde et al., 2017). Key challenges in modeling transportation include sectoral heterogeneity, technical complexity, representation of consumer travel behavior, and data availability (Tavasszy et al., 2011; Yeh et al., 2017; Zhang et al., 2018). In addition, previous literature has suggested the transportation sector offers relatively less potential for substantial changes in technology than other components of the energy system, citing limited cost-competitive fuels (Mathiesen et al., 2015). However, recent advancements in vehicle technology, especially electric vehicles (EVs), provide motivation to update assessments of the transportation sector's potential for substantial shifts in emissions and energy consumption. Passenger and freight transportation services typically rely on long-lived vehicles with a variety of important physical attributes, including, but not limited to, energy type, energy efficiency, range, capacity, and lifetime. Each of these vehicle attributes requires some level of definition in transportation modeling to accurately simulate energy, emissions, and economic outcomes. The consumer value of vehicles is determined by their age and their energy requirements, performance characteristics (e.g., power/torque), and other amenities (e.g., comfort/safety) (Greene et al., 2018). Cost and consumer utility trade-offs associated with vehicle attributes (e.g., between capital cost and vehicle range) can be challenging to analyze when modeling vehicle consumer choices. Taken together, transportation system complexities can quickly outstrip data availability and model computational capabilities and therefore generally require a significant amount of simplification. Modelers looking to represent additional transportation sectoral, technological, and spatial detail as part of a larger modeled economic system face trade-offs under constraints from numerical solution algorithms and computing power limitations. Computable general equilibrium (CGE) models typically use standard economic data from national income accounts and offer a rich set of endogenous economy-wide feedback, but they generally do so at the expense of subsectoral detail and specific individual technology characteristics, and most CGE models are constrained in the amount of technological detail they can incorporate. Thus, balancing the trade-offs of adding in the technological and spatial details of transportation sector-only models while gaining the insights from an economy-wide CGE perspective requires some degree of modelers' judgment. Despite these challenges, enhancing representation of the transportation sector within CGE models may improve understanding of potential economy-wide impacts of future shifts in energy and transportation service consumption. Prior work (Wade et al., 2019; Zhang et al., 2018; Britz and van der Mensbrugghe, 2016) has shown that aggregation of technological and spatial detail in economic models can mask important sources of heterogeneity, potentially leading to substantially different predicted outcomes between models employing different levels of aggregation. In CGE models, this is sometimes labeled “aggregation bias.” For example, Cai and Arora (2015) explored the importance of disaggregating electricity generation in a CGE model when assessing the impacts of environmental policy, finding that incorporation of heterogeneous generation technologies has important effects on the estimated cost of mitigation. Within the transportation sector, there are opportunities for passenger and freight mobility demands to substitute among modes (e.g., between freight services provided by truck, rail, and marine shipping) and energy technologies (e.g., petroleum, battery electric, hydrogen fuel cell electric). Aggregating these modes and representing only conventional technologies, as many CGE models do, prevent substitution, either by fixing market shares for modes and/or technologies or by allowing only for exogenous changes in market shares. This reduced flexibility limits options for modeling how the economy adjusts to economic and policy shocks or long-term developments in the transportation sector. Even if technologies' cost structures are expected to remain constant over time, modeled shifts in resource costs or other exogenous macroeconomic shocks can still affect technologies' competitiveness. Models with single-technology and aggregated-mode representations that do not allow for endogenous substitution among alternative technologies and modes of transport are likely to find different economic outcomes than models that allow such competition through more detailed representation. https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 2/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect To study the potential significance of more detailed transportation technology and sectoral representation in economy-wide modeling, we disaggregated transportation sector modes in the Applied Dynamic Analysis of the Global Economy (ADAGE) global CGE model and incorporated technologies representing multiple types of alternative-fuel vehicles (AFVs). We then compared results between two versions of the model that incorporate disaggregated transportation modes, both with and without the addition of AFVs. Incorporating AFV technologies (version 1) has a substantially larger impact on energy and emissions results than disaggregating transportation modes alone (version 2); therefore, we focus on comparing model results with and without AFV technologies in the results and discussion sections (see Fig. A1 in Appendix A). The scenarios presented in this study are based on illustrative oil price trajectories, a key driver of transportation service costs for traditional vehicles with internal combustion engines. We found including new vehicle technology options for on-road transportation modes in ADAGE leads to differences in the modeled mix of transportation energy demand, energy intensity of transportation services, and total greenhouse gas (GHG) emissions. Specifically, we found that (1) on-road vehicle electrification can significantly reduce emissions with concomitant electricity sector decarbonization, (2) higher (or lower) oil prices can hasten (or slow) the transition to EVs with hybrid vehicles moderating the transition, and (3) representation of AFV technologies is essential for capturing these changes. These differences illustrate the economic and environmental significance of sectoral technology representation in economy-wide models. These findings may inform future studies of modeled technology competition and environmental impact assessments of the transportation sector. 2. Literature review The global transportation sector is a large and growing user of energy and a major source of associated emissions (Intergovernmental Panel on Climate Change, Edenhofer, Pichs-Madruga et al., 2014) and health impacts (Anenberg et al., 2019). Thus, transport is a vital component of energy systems and energy-environment modeling and is typically represented in detail within energy system models. Energy demands from transportation may shift through several pathways, including changes in transport demand, shifts in demand among the different modes of travel, reductions in energy intensity of vehicle technologies, and adoption of new vehicle technologies and fuel types (Creutzig, 2015). Transportation-only sector modeling studies often analyze specific pathways and components of this system (e.g., a single-fuel production pathway, a single-sector technology adoption, specific refueling infrastructure) without capturing key market interactions important for understanding the implications for the overall energy system (Muratori et al., 2020). Although the number of studies assessing global transport has increased in recent years, they have tended to limit the analysis to the light-duty vehicle (LDV) sector (Meyer et al., 2007; Grahn et al., 2009; Kyle and Kim, 2011; Karplus et al., 2013a; Bosetti and Longden, 2013; Hao et al., 2016; Edelenbosch et al., 2017; Green et al., 2019). Several energy system models represent the full transportation sector, but many of these models lack full integration with the rest of the economy (Grahn et al., 2013). Capturing the whole economy is especially useful both for understanding freight demand, which is closely tied to gross domestic product (GDP), and when considering the potential for transport electrification, because increasing the use of EVs also increases electric power demand. The mix of generation technologies (e.g., coal- or natural gas-fired electricity/renewable sources of power such as wind and solar) used to meet an increase in electricity demand could significantly influence other markets (e.g., capital, energy) and overall energy and emissions outcomes. Energy-focused, economy-wide models have frequently been used to capture costs and energy use over broad spatial (e.g., country/global) and temporal scales (e.g., mid-century and/or end-of-century time frames), including interactions across markets. As previously noted, given the importance of transportation for energy demand in the United States and globally, most energy-focused economy-wide models include transportation modules. Some of the models that fall under this category are integrated assessment models such as the Global Change Analysis Model (GCAM) (Pacific Northwest National Laboratory, 2021), Model for Energy Supply Systems and Their General Environmental Impact (Huppmann et al., 2019; “MESSAGEix model & framework”, MESSAGE), Prospective Outlook on Long-term Energy System (POLES) (Després et al., 2018), and Regional Model of Investments and Development https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 3/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect (REMIND) (Luderer et al., 2015); energy-economy-environment-engineering models such as CIMS (Jaccard, 2009), Energy System Modeling Environment (“ESME”) (Heaton, 2014), National Energy Modeling System (NEMS) (Nalley et al., 2019), and The Integrated MARKAL-EFOM System (TIMES) (Loulou et al., 2005); and CGE models such as AsiaPacific Integrated Model (AIM) (Akimoto et al., 2015), Economic Projection and Policy Analysis (EPPA; Paltsev et al., 2005), General Equilibrium Model for Economy-Energy-Environment (GEM-E3) (Capros et al., 2013), and IMACLIMR (Sassi et al., 2010; Waisman et al., 2012).1 Although these energy-focused economy-wide models may be well suited for modeling long-term impacts of alternative technology, policy, and market outcomes, most models characterize transportation at a relatively aggregate level, particularly CGE models. Aggregating, or averaging, across scales is generally necessary for representing physical and economic parameters at the level of sectoral, regional, and production technology detail used within these individual models. Aggregation is also important for aligning data available at different scales and making models computationally tractable. However, there are important trade-offs, including potential bias, that can result from combining and averaging across heterogeneous input data. Multiple studies have identified potential issues related to aggregation bias, which refers to the possibility that model results will systematically differ as a function of the level of aggregation (Britz and van der Mensbrugghe, 2016; Caron, 2012; Himics et al., 2020; Horridge, 2018; Wade et al., 2019; Zhang et al., 2018). The literature suggests that certain key model results, such as trade and welfare changes, depend on the aggregation level selected (Ko and Britz, 2013), and significant differences may exist at the subsectoral level (Alexeeva-Talebi et al., 2012; Zhang et al., 2018). Brockmeier and Bektasoglu (2014) conducted a sensitivity analysis using different aggregations on general equilibrium (GE) and partial equilibrium (PE) versions of the Global Trade Analysis Project (GTAP) model and found that data aggregation, especially sectoral aggregation, has a much larger influence on results than model structure from GE and PE. Although the potential for model results to differ based on level of aggregation has been recognized, relatively few studies have attempted to quantify the magnitude of these impacts (Britz and van der Mensbrugghe, 2016). Transportation inherently involves movement of people and goods across space and thus may be impacted by the level of spatial disaggregation modeled and assumptions regarding the movement of people, goods, and services across regions. Several studies have conducted comparisons across multiple global transportation models, exploring projections under baseline and various emissions mitigation scenarios (Edelenbosch et al., 2017; Girod et al., 2013; Pietzcker et al., 2014; Yeh et al., 2017). The models compared in these studies typically project a large increase in demand for transportation services over the next few decades with technological change having a major influence on future energy consumption and emissions. Typically, these models show substantially reduced transportation energy use and emissions in their projections only when they incorporate advanced technologies that are less energy intensive or GHG intensive than incumbent technologies. In general, there is considerable uncertainty regarding model baseline projections, as well as future changes in transportation energy intensity and emissions under alternative scenarios. Key drivers of uncertainty include global demand for transportation, vehicle capital cost projections, fuel prices, nonprice factors affecting adoption of new technologies, potential for modal shifts, and the availability and influence of transportation infrastructure. These studies include relatively few CGE models, although the AIM/CGE, GEM-E3, and IMACLIM-R models have been used in these types of comparisons. The EPPA model is another CGE model that has been widely used in transportation-focused studies (Paltsev et al., 2004; Schäfer and Jacoby, 2005; Karplus et al., 2013b; Karplus et al., 2010; Green et al., 2019). As the costs of AFVs, such as EVs, have come down, modeling scenarios have placed greater emphasis on the energy impacts and environmental benefits they offer. As a result, EV technologies have taken an increasingly prominent role in projections of the future transportation sector. Still, most CGE models generally provide limited representations of alternative-fuel technologies, although notable exceptions include the EPPA (Karplus et al., 2010; Karplus et al., 2013b) and GEM-E3 (Karkatsoulis et al., 2017) models. For example, EPPA disaggregates household transportation from the overall transportation sector and introduces battery and plug-in hybrid vehicles to compete with conventional vehicles within the model. Table 1 summarizes the model structural attributes' sectoral detail for transportation and electricity for a set of identified energy-focused economy-wide CGE models. Although https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 4/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect technology details for the electricity sector and transportation sector modal disaggregation are common, relatively few models have rich advanced technology details in their transportation sectors. Table 1. Economy-wide CGE models' transportation attributes. Model Institution Model Dynamics Country Time Capital Coverage Frame Vintaging Transportation Modes Power Advanced Refere Technology Technology ADAGE RTI Recursive- Global/8 5-year dynamic regions Yes Light duty, Hybrid, interval freight truck, natural gas, technologies: (2023) 2010– bus, air, water, battery, coal, oil, gas, 2050 rail freight, combined fuel cell, 9 rail passenger, hydrogen cycle, hydro, and rest nuclear, for all on- Cai et a road modes solar, wind, geothermal AIM/CGE NIES Recursive- Global/17 1-year Yes Car, bus, rail, N/A 12 Fujimo dynamic regions interval domestic air, technologies: (2017) 2005– international coal, oil, gas, 2100 air, two- nuclear, wheelers hydro, geothermal, photovoltaic (P)V, onshore wind, offshore wind, waste, other renewables, advanced biomass Dart EC-MSMR KIEL Recursive- Global/20 1-year Institute dynamic regions Grouped with N/A Coal, natural Jin et a interval other in the gas, hydro, (2019) for World 2011– mobility nuclear Economy 2030 sector ENV Recursive- Global/16 5-year Canada dynamic regions interval Yes Yes Air and other transport N/A 11 Zhu et technologies: (2018) 2010– fossil fuel 2050 based, nuclear, hydro, wind, solar, geothermal, biomass, coalintegrated gasification with carbon capture, https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 5/46 2023/5/12 11:11 Model Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Institution Model Dynamics Country Time Capital Coverage Frame Vintaging Transportation Modes Power Advanced Refere Technology Technology natural gas power generation with carbon capture, biomass power generation with carbon capture, solar power generating with storage ENGAGE UCL Recursive- Global/17 2007– dynamic regions 2030 No Air, water, N/A 1 sector other Winni al. (201 transport ENVISAGE GTAP Recursive- Global/ Flexible Yes Air, water, dynamic flexible with step other Mensb transport (2018) 20–30 regions ENV- OECD Linkages Recursive- Global/29 Extends Yes dynamic regions to 2050 1 sector N/A N/A 1 sector 7 van de Châtea technologies: (2014) fossil fuel based, hydro and geothermal, nuclear, solar and wind, and renewable combustibles (including biomass) and waste, gas carbon capture and sequestration (CCS), coal CCS EPPA MIT/US Global/18 5-year EPA regions interval Yes LDVs, other LDV 18 “EPPA transport includes technologies: Structu 2010– ICE, battery coal, natural (MIT Jo 2100 electric, gas, oil, Progra hydrogen, advanced the Sci plug-in gas, and Po electric advanced Global https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 6/46 2023/5/12 11:11 Model Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Institution Model Dynamics Country Time Capital Coverage Frame Vintaging Transportation Modes Power Advanced Refere Technology Technology coal, coal Chang with CCS, 2023) coal + bio cofiring with CCS, gas with CCS, gas with advanced CCS, nuclear, advanced nuclear, hydro, solar, wind, wind with backup, solar with backup, biomass, biomass with CCS EU-EMS PBL Recursive- Global/67 2010– dynamic regions 2050 No Grouped in N/A 1 sector other sectors (Niam 2020, Thisse 2019) EXIOMOD TNO CGE Global/44 2015– Rail, other N/A 12 (Ivanov countries and 2050 land, sea and technologies: 2019) a Rest of coastal water, coal, gas, Bulavs World inland water, nuclear, al. (201 air, rest hydro, wind, oil, biomass and waste, solar PV, solar thermal, wind, geothermal, other FARM USDA Recursive- Global/13 2004– Air, water, dynamic regions 2050 other N/A 9 (Sands technologies Sands with one for 2014) bioelectricity using switchgrass Gdyn GTAP Dynamic Global/12 regions https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 No Land, air, water N/A 1 sector Antim al. (201 7/46 2023/5/12 11:11 Model Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Institution Model Dynamics Country Time Capital Coverage Frame Vintaging Transportation Modes Power Advanced Refere Technology Technology GEM-E3 JRC Recursive- Global/38 5-year Yes Air, road EVs 11 Capros dynamic regions interval passenger, rail technologies: (2013) 2011– passenger, coal, oil, gas, 2050 water nuclear, passenger, biomass, road freight, hydro, wind, rail freight, PV, water freight geothermal, CCS coal, CCS gas ICES IGEM CMCC Recursive- Global/25 1-year dynamic regions Insight- Inter- works temporal No 1 sector N/A Coal, gas, oil, “ICES” or 5- nuclear, tempo year hydro, solar, Compu interval wind Equilib 2011– System 2050 (ICES, US No Grouped in N/A 1 sector the Goettle (2009) transportation and warehousing sector IMACLIM-R MAGNET CIRED Hybrid Global/12 1-year dynamic regions interval Yes Air, water, N/A 1 sector other (Sassi 2010) through the 2001– (Waism recursive 2100 al., 201 iteration of “Mode annual static concep equilibria solver and dynamic details modules IMACL recursive- (UCL W dynamic 2014) LEI Global No N/A Woltje (2014) MAGNET LEI Recursive- Global/134 dynamic regions and No Air, water, N/A 1 sector other Philipp al. (201 countries MIRAGE-e CEPII Recursive- Global/19 Up to dynamic regions 2100 No 2 sectors: car N/A and truck, Coal, oil, gas Fontag al. (201 other MIRAGRODEP IFPRI Recursive Global/141 region or country https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 Yes Air, water other N/A “The MIRAG Model 8/46 2023/5/12 11:11 Model Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Institution Model Dynamics Country Time Capital Coverage Frame Vintaging Transportation Modes Power Advanced Refere Technology Technology nation Policy Resear Institu (IFPRI) PACE ZEW Comparative- Global/50 static No regions Grouped in N/A energy Grouped Clauss with heat Schube intensive (2009) sector REMIND SAGE PIK EPA Inter- Global/11 5-year temporal regions Inter- U.S./4 regions temporal LDVs (internal N/A 14 interval combustion technologies: (2015) 2005– engine coal, gas, oil, 2100 battery coal with electric CCS, gas with vehicle (BEV) CCS, and fuel cell bioenergy, vehicle), bioenergy passenger with CCS, train, heavy- geothermal, duty freight, nuclear, passenger- hydro, solar, aviation and solar-central buses, electric PV, solar-CSP, rail wind 5-year Yes Yes interval Truck, No 1 sector nontruck Ludere Marten (2021) 2016– 2081 SNoW-NO TEA Statistics Recursive- Norway dynamic Norway 1-year No Air, water, interval public 2013 transport, beyond other PPE/ Recursive- Global/18 5-year COPPE dynamic regions interval No Air, water, N/A 1 sector Lindho (2019) N/A 1 sector other Cunha (2020) 2011– 2100 USREP MIT Recursive- U.S./11 or 30 5-year dynamic regions interval 2006– 2100 Yes Personal and Battery, 8 USREP commercial plug-in technologies: et al., 2 hybrid conventional, biomass, wind and solar, wind with gas backup, wind with biomass https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 9/46 2023/5/12 11:11 Model Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Institution Model Dynamics Country Time Capital Coverage Frame Vintaging Transportation Modes Power Advanced Refere Technology Technology backup, advanced gas, advanced gas with CCS, advanced nuclear WEGDYN_AT Wegener Static- Global/Austria No Motorized Center comparative individual and transport, five recursive- land transport dynamic (rail freight, mode rail passenger N/A Grouped in “WEGD other sector (Sentin 2023) long-range, road freight, short range public transport, other transport services) (e.g., postal services, warehousing), air, water 3. Methodology 3.1. ADAGE model overview The ADAGE model is a multiregion, multisector, recursive-dynamic CGE model. ADAGE follows the classical ArrowDebreu GE framework (Arrow and Debreu, 1954) covering all aspects of the economy, including factor endowments, production, private and public consumption, trade, and investment. ADAGE includes eight regions (Africa, Brazil, China, European Union 27, United States, Rest of Asia, Rest of South America, and Rest of World) and simulates regional and global economic activity from 2010 through 2050 in 5-year increments. Intertemporal dynamics in ADAGE are represented by (1) growth in the available effective labor supply from population growth and changes in labor productivity; (2) capital accumulation through savings and investment; (3) changes in stocks of natural resources; and (4) technological change from improvements in energy efficiency, productivity, and advanced technologies (e.g., AFVs) that become cost competitive in later time periods. Within each period, representative firms in each sector maximize profits subject to technology constraints also specified by a constant elasticity of substitution (CES) functional form. This production structure guides the transformation of factors of production and intermediate inputs into commodities. The model includes more than 60 sectors with distinct representations of fossil fuels, electricity generation technologies, and transportation modes. One representative household per region allocates its earnings to consumption of these commodities and investment. The composition of consumption of goods and services is responsive to relative prices and is guided by https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 10/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect a nested CES function. Households allocate their time to earning income in labor markets and enjoying leisure, and the relative prices of consumption and labor hours (i.e., wages) guide their allocation. ADAGE represents bilateral trade flows among regions; households and firms exhibit preferences between consumption goods by origin (i.e., domestic versus foreign) via Armington aggregation (Armington, 1969). ADAGE tracks environmentally important inputs and outputs (e.g., land, fuels, emissions) in physical and monetary units. The representation of the economy with rich sectoral detail makes ADAGE suitable for analyzing a wide range of economic and environmental policies and estimating how all parts of an economy respond to those policies (Clarke et al., 2016; Calvin et al., 2016; Lucena et al., 2018; Kober et al., 2016; van Ruijven et al., 2016). The core database underlying ADAGE is GTAP version 7.1 (Narayanan and Walmsley, 2008), complemented by numerous other data sources to extend the physical and technological detail in ADAGE. This study is the first application of a new version of ADAGE with an enhanced version of the transportation sector. Thus, in this paper we focus on describing the modifications introduced to the transportation and energy sectors. See (Cai et al., 2023) for full documentation of the ADAGE model, including detailed discussion of our additions and modifications to the data available from the GTAP database. 3.1.1. Production in the transportation sector The transportation sector in ADAGE includes (1) eight modes of transportation that use conventional technologies (light-duty passenger, passenger buses, heavy-duty freight, rail freight, rail passenger, airline, water transportation, and other transportation) and (2) four types of AFV technologies (battery electric vehicles [BEVs], hybrid vehicles, compressed natural gas vehicles, and hydrogen fuel cell EVs) for all on-road transportation. On-road vehicles were assumed to have a maximum useful lifetime of 30 years in the model, and the average survival rate was lower for LDVs than for passenger buses and heavy-duty freight. The production of transportation service for each on-road mode and technology in ADAGE is vintaged: new vehicles were defined as those from age zero years through the end of age 4, and used vehicles were defined as vehicles age 5 years or above. Production of new vehicles using conventional and AFV technologies is structured with a series of nested CES functions using energy, capital, labor, and materials as inputs (see Fig. 1). Energy used in transportation varies by mode and technology, as shown in Fig. 2. Currently, most finished gasoline in the United States contains up to 10% ethanol by volume (E10), whereas a smaller amount of biodiesel is blended into petroleum diesel. Overall, biofuels accounted for about 5% of total U.S. energy consumption in the transportation sector in 2020; ethanol supplied about 4% and biodiesel and renewable diesel combined supplied about 1% (Energy Information Administration (EIA), 2019). For this study, first- and second-generation biofuels can be blended with refined oil and replace refined oil used in all on-road transportation modes. The fuel blending ratio differs for LDVs, freight trucks, and passenger buses with relatively more ethanol than biodiesel in LDVs and more biodiesel in heavy-duty vehicles. Refined oilbiofuel blends and electricity were used in hybrid vehicles at a fixed ratio to represent the average hybrid vehicle in each global region. Because hydrogen is not presently modeled as a commodity in ADAGE, we collapsed the production of hydrogen, which uses electricity and natural gas as inputs, and the production of transportation service, which uses hydrogen and other inputs, into one composite production function for fuel cell technology. Natural gas vehicles represent the combination of natural gas–only vehicles and bi-fuel vehicles (gasoline and natural gas), where natural gas and refined oil cannot substitute with each other in ADAGE. Battery vehicles use electricity and do not differentiate the electricity source (fossil fuel or renewables). In general, battery vehicles have the highest energy efficiency, followed by fuel cell vehicles, hybrid, and conventional. Natural gas vehicles have the lowest fuel efficiency (see Table A1 in Appendix A). https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 11/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Download : Download high-res image (114KB) Download : Download full-size image Fig. 1. New on-road transportation production structure by mode and technology. This figure depicts the production structure for new on-road transportation vehicles by mode and technology by displaying its inputs and connecting them with lines to indicate how they are combined in the production function. Each vertex includes inputs whose substitution is parameterized by the elasticity displayed for that vertex. Download : Download high-res image (139KB) Download : Download full-size image Fig. 2. Energy used in on-road transportation by technology. This chart shows the included fuel or energy type used in on-road transportation. Conventional includes oil and biofuels. Battery, hybrid, and fuel cell include electricity. Hybrid and gas include oil-biofuel. Fuel cell and gas include natural gas. For each new vehicle technology, the energy mix bundle can substitute with capital to improve energy efficiency. The resulting energy/capital composite was then combined with materials and labor within a Leontief production function (i.e., assuming no substitution between these inputs). A fixed factor was included for new vehicle production with an elasticity of substitution of 0.1 (fuel cell vehicles and natural gas) or 0.2 (battery and hybrid electric) at the top level of the production function (see Fig. 1 for the new vehicle production structure). The fixed factor was assumed to be 0.1% of service production value with an equivalent endowment in 2010. As the model solves for later periods, the endowment is updated to larger or smaller values based on the solution from the previous period. The approach for defining the fixed factor reflects the fact that retirement of conventional technology and adoption of AFVs are both determined by more than cost per mile traveled. The fixed factor acts as a https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 12/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect proxy for the cost and availability of supportive infrastructure, infrastructure network externalities, consumer preferences regarding vehicle technologies, and other nonpriced factors that might slow AFV adoption beyond what an input cost-per-service basis would imply. Fixed factor parameterization is commonly accomplished through modeler judgment (Chen et al., 2022). Moreover, elasticity estimates for nascent technologies may not be reliable for later periods with higher penetration. The rate of technology penetration is an important sensitivity for model calibration worthy of further study. Vehicle technologies in the U.S. region are subject to national fuel efficiency standards. More specifically, we assumed that the U.S. region transportation sector must meet the Phase 2 fuel efficiency and GHG emissions standards for both light-duty and heavy-duty vehicles (Environmental Protection Agency et al., 2016; National Highway Traffic Safety Administration, 2010). For our representation of the real-world fuel economy levels required to meet these standards, we relied on average fuel economy projections for LDVs, freight trucks, and buses from the Annual Energy Outlook (AEO) 2018 Reference Oil Price case, which assumes full compliance with these standards (U.S. Department of Energy, Energy Information Administration (EIA), 2018). These assumed average fuel economy levels must be met on average across all new vehicles sold, so no one vehicle technology need satisfy the standard unless there is only one technology. To model the fuel efficiency standards, technologies purchase credits for their fuel use and produce credits at the rate implied by the efficiency standard. Thus, technologies more efficient than the standard are subsidized at the expense of less efficient technologies, the latter of which must purchase more credits than they produce. The model structure and elasticity of substitution are described in the ADAGE documentation (Cai et al., 2023). To characterize AFVs in each mode where they are available (e.g., LDVs, heavy-duty vehicles, buses), we used a bottom-up approach to obtain vehicle purchase costs, expenses for charging stations and other infrastructure, vehicle insurance, maintenance costs, and fuel economy over time and to see how they change relative to each vehicle's conventional counterpart. The parameter values used in this work were informed by external data, including Department of Energy battery pack and fuel cell stack technology, interim and ultimate target fuel intensity, and costs (U.S. DOE, 2015; Nykvist and Nilsson, 2015; BNEF, 2015), and AEO 2019 data (Energy Information Administration (EIA), 2019). We reviewed near-term battery pack cost estimates by extrapolating from Nykvist and Nilsson (2015) to 2020 and then to mid-century using U.S. DOE (2015) 2050 estimates. Our battery pack costs are therefore drawn from a variety of sources to construct illustrative, forward-looking estimates combined by the authors' expert judgment. The authors have developed plausible values of future vehicle efficiency and cost for use in scenarios demonstrating the novel transportation sector methods employed in ADAGE and reported in this paper. However, these estimates do not constitute a projection of future vehicle costs or efficiencies and should not be interpreted in such a manner. AFV purchasing costs were aggregated to capital, labor, and materials inputs in ADAGE. Purchase and infrastructure costs were amortized into annual capital costs using an assumed 30-year maximum lifetime for all on-road vehicles. Energy input cost was derived from energy price in the ADAGE base year and fuel economy. The sum of labor, capital, materials, and energy input costs form the transportation service production cost and vary by region of the world. Error! Reference source not found.32 provides a comparison of production cost per mile traveled for all new on-road vehicles in the United States. For conventional vehicles, the cost reduction is induced by fuel efficiency improvements only, whereas for AFVs, cost declines also stem from technology improvements that reduce capital, labor, and material costs. We assumed battery, hybrid, and fuel cell vehicle costs decline over time. One or more of these AFVs become cost competitive with conventional vehicles by 2030, although the trajectories vary by mode. The current pace of change for AFV costs in these sectors is rapid, and any cost estimates will likely change in the future. Still, these figures show the types of inputs required to operationalize and demonstrate the validity of these methods. The transportation service production cost (e.g., energy, capital, insurance, maintenance, and infrastructure costs) for new vehicles was updated in each period in the model using data in Fig. 3. The new vehicle's fixed-factor endowment in each current period was assumed to be proportional to its service production in the previous time period. The service production cost for used vehicles was guided by the age structure of vehicles added in prior https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 13/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect periods. In ADAGE, a vintaged capital stock serves a comparable role to the fixed factor in new vehicles, which is not present for used vehicles. ADAGE transportation service production for used vehicles (aged 5–29 years) for both conventional and alternative-fuel technologies use the same set of energy, capital, labor, and materials inputs as when a given vintage of used vehicle was new with no substitution possibilities (i.e., the input mix is determined when new vehicles are produced, but can no longer be changed once they have been made). Therefore, the used fleet efficiency can only be improved by the retirement of old vehicles and the adoption of new, more efficient vehicles. ADAGE's relative proportions of vehicle miles traveled (VMT) being provided by vehicles in each vintage are determined by the number of new vehicles added in each prior period adjusted for the average VMT driven by vehicle age. ADAGE's vehicle survival rate combined with a VMT schedule for surviving vehicles by age (in annual time steps) informs the weighting of surviving vehicle attributes (e.g., fuel efficiency, nonfuel costs) in the vintage stock, with data coming from the Motor Vehicle Emission Simulator (MOVES) (2014a) model developed by the U.S. Environmental Protection Agency. Vehicle survival rates and annual VMT decline as vehicles age, reducing the relative influence of older vehicles on the vintage fleet efficiency. Conventional vehicles and AFVs were assumed to have the same average VMT schedule. Download : Download high-res image (280KB) Download : Download full-size image Fig. 3. Transportation service costs for all new on-road vehicles in the United States during 2010–2050 ($/VMT). This line graphs shows US$ per vehicle mile traveled (VMT) for each model year from 2010 to 2050. Lines represent conventional and electric vehicles and are separated by light duty, freight truck, and bus. Bus has the highest $/VMT for all vehicle types, followed by freight then light duty. Both conventional and electric vehicles $/VMT drops from 2010 to 2050, with a substantial drop for fuel cell and battery. 3.1.2. Demand for transportation services Transportation services are demanded by producers, governments, and households. For producers and governments in ADAGE, transportation services enter a Leontief structure, meaning, for example, that there is no substitution between on-road freight and rail freight transportation (taken as a simplifying assumption). The ADAGE model uses a nested CES structure to represent household consumption preferences. In each period, households generate utility from consumption of leisure and composite goods (see Fig. 4). A composite good, aggregated from housing, food, manufacturing, transportation, and others, can be traded against leisure time to obtain a specific utility for each household in each period. The elasticity of substitution between the composite good and leisure (σcl) represents how willing households are to trade off leisure time for consumption (i.e., sacrifice leisure time to earn a wage and purchase more consumption goods and services). Within the composite good, transportation is substitutable with an other goods aggregate consisting of a combination of all other goods, including housing and an aggregate of food, other goods, and services with an elasticity of substitution, σch, equal to 1.0. The food, goods, and services aggregates have an elasticity of substitution, σc, of 0.5. Housing includes an energy bundle (coal, gas, electricity, and oil) with https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 14/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect an elasticity of substitution, σhe, of 0.5. Within housing, energy and capital have an elasticity of substitution, σhk, of 1.0. The demand structure and elasticity of substitution above are discussed in the ADAGE documentation (Cai et al., 2023) and shown in Fig. 4. Download : Download high-res image (411KB) Download : Download full-size image Fig. 4. Model structure for household demand. This figure depicts the structure for household demand by displaying its inputs and connecting them with lines to indicate how they are combined in the household utility function. Each vertex includes inputs whose substitution is parameterized by the elasticity displayed for that vertex. Transportation aggregates, composed from passenger transportation and nonpassenger transportation, substitute with an aggregate of all other goods and services at an elasticity of 0.5 (σct). Households cannot substitute between freight and passenger transportation (σtr = 0) nor among modes of freight (e.g., water, train, truck, and other; σtf = 0). Household substitution among passenger modes (e.g., airline, bus, train, and auto) is possible with a substitution of σtp = 0.5. Within transportation modes, transportation vintages and technologies produce undifferentiated goods that compete freely with one another (implied elasticity σtpf = ∞) constrained only by their fixed factor and capital stocks. Transportation service demand in each region is a function of GDP per capita, population, and region-specific preferences among travel modes. Based on (Dargay et al., 2007), we used the S-shaped Gompertz function to project the relationship between vehicle ownership growth rate and per capita income, urbanization, and population for all ADAGE regions over the model horizon. The calculated trend in vehicle ownership was then used to calibrate ADAGE's trend in household demand for light-duty and passenger bus transportation service as a fraction of income over time. Household passenger service demand is mainly driven by population growth in the United States with modest per capita VMT growth, whereas in China and Africa, both GDP and population growth drive VMT growth rates. The passenger vehicle ownership growth trend is shown in Table A2 in Appendix A, with more details presented in the ADAGE documentation (Cai et al., 2023). 3.1.3. Electricity production and the energy sector https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 15/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect The rapid cost reduction of AFVs in recent years and assumed in the future (Fig. 3) indicates that AFVs may take an increasingly significant role in the transportation sector in the future. The substitution of other energy sources, especially electricity for liquid fuels, means that representation of future energy production plays a vital role in analyzing changing technologies in the transportation sector and in determining implications for net GHG emissions. Ten electricity generation technologies (conventional coal, natural gas, refined oil, combined cycle natural gas and renewable electricity from solar, wind, nuclear, hydro, geothermal, and biomass) are included in ADAGE. Each technology has an independent CES production function. ADAGE includes fixed factors of production in the top nest of the electricity production function for renewable and combined cycle natural gas generation. Price competition across different electricity generation technologies is limited by an aggregation elasticity. Consumers purchase one undifferentiated electricity good. The electricity generation cost for these technologies was taken from the 2020 Annual Technology Baseline from U.S. National Renewable Energy Laboratory (2020). In the energy sector of ADAGE, fixed factors are incorporated into the production functions for coal, natural gas, and crude oil used to represent natural resource constraints. Crude oil is assumed to be a homogeneous product trading at a single world price, with adjustments for tariffs, export taxes, and transport margins. Armington aggregation differentiates between coal, gas, refined oil, and electricity from domestic production and imports from other regions of the world. 3.2. Scenario implementation In this paper, we present two versions of ADAGE: the NoAFV version, which includes eight modes of transportation (auto, freight truck, bus, air, rail freight, rail passenger, water, and all other transportation) with only conventional technologies available for all modes, and the YesAFV version, which includes the same eight modes of transportation as NoAFV and incorporates AFV technologies in all modes of on-road transportation (auto, bus, freight trucks) in all regions. Technology costs in the NoAFV version are representative of conventional technologies. In the base year of the YesAFV version, only conventional technologies are calibrated to be operating, but new vehicles are chosen endogenously based on cost, meaning AFVs could be produced immediately if economical. We then present illustrative oil price scenarios under the hypothesis that different assumptions about long-term future oil prices will significantly affect the modeled energy and transportation system results for each ADAGE version. The crude oil price paths in these sensitivity scenarios were taken from the U.S. EIA 2018 AEO, specifically the Reference Oil Price case (referred to hereafter as REF), High Oil Price case (hereafter HOP), and Low Oil Price case (hereafter LOP) (see Fig. 5).3 Download : Download high-res image (128KB) Download : Download full-size image Fig. 5. Crude oil price cases from AEO2018 (2010$/Barrel). This line graph shows the crude oil price in 2010$ for each model year (2010 to 2050). The low oil price (LOP) case declines from 2010 to 2020, then experiences a slight incline each year after. The reference (REF) case and high oil price (HOP) case show an increase in price for all years with the greatest increase occurring until 2025. https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 16/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Those oil price cases assume a range of exogenous global crude oil price paths for each model version. The REF represents an increasing trend projection for both global oil supply and demand with crude oil prices rising steadily across the projection period from $62/barrel in 2020 to $101/barrel in 2050. The HOP and LOP encompass a wide and asymmetric range of crude oil prices to demonstrate ADAGE behavior under an array of plausible fuel price paths. Prices diverge after 2015, bounding the REF price path and illustrating variations in modeled global demand for and supply of, among other things, petroleum and other liquid fuels, energy as a whole, and transportation service. 4. Results In this section, we examine how adding alternative-fuel technologies alters the ADAGE REF case results for VMT, vehicle stock fuel efficiency, energy markets, and GHG emissions. Although ADAGE is a global model, we focus on results for the United States. We then examine technology trends across transportation modes under AEO 2018 REF, LOP, and HOP to understand how changes in oil prices can alter U.S. economic and environmental outcomes such as changes in VMT, AFV adoption, and GHG emissions. As ADAGE's 5-year time steps model economic behavior for a representative year within the period, the results shown do not correspond to the exact year for which they are reported (e.g., 2020, 2025). ADAGE results are most comparable to the average economic activity for the year presented and the four years following it (e.g., the 2020 time step is an average of 2020–2024). Our model simulations of these scenarios are intended to illustrate the sensitivity of transportation technology adoption to different market outcomes. Our results are not intended to project or exactly replicate real economic outcomes. The value in this sort of modeling is to understand insights from economic outcomes by order of magnitude, direction, and relative change, but not in exact levels. 4.1. Reference oil price scenario 4.1.1. U.S. VMT In both versions of our REF case, the NoAFV version and the YesAFV version, VMT grows for each vehicle type over time (Fig. 6). In the NoAFV version, U.S. light-duty VMT demand comes mostly from households, and the growth rate of 0.7% per year (from 2613 billion miles in 2020 to 3180 billion miles in 2050) reflects ADAGE's calibrated decline in households' transportation demand per unit of consumption over time. Freight truck demand is proportional to U.S. economic output, and its growth rate is the highest of the three on-road modes (1.8% per year, resulting in an increase from 301.5 to 511.3 billion miles between 2020 and 2050). Passenger bus demand grows by 1.3% per year (from 9.9 billion miles in 2020 to 14.4 billion miles in 2050). Download : Download high-res image (343KB) Download : Download full-size image https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 17/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Fig. 6. Vehicle miles traveled in the United States, reference oil price projections (billion VMT). This bar chart shows total vehicle miles traveled (VMT) for light duty, freight truck, and bus. Bars include stacked components representing conventional and alternative fuel vehicles and are separated by YesAFV and NoAFV. Total VMT is completely replaced by hybrid or battery vehicles s by 2050 in the YesAFV version, and conventional is substantially reduced in 2040 for light duty vehicles (1339 billion VMT in 2030 to 242 billion VMT in 2040). Including additional technologies in the model in the YesAFV version results in faster growth in LDV (0.9% per year) and passenger bus demand (1.1% per year) and a decline in the growth of freight demand (1.7% versus 1.8% per year in the NoAFV version). The YesAFV version also results in 100% replacement of conventional vehicles by hybrids and BEVs by 2050 across auto, freight truck, and passenger bus modes (Fig. 6). As described in Fig. 3 above, based on our assumptions about improvements in their efficiency and declining capital costs, total transportation service cost for BEVs and hybrids becomes lower than conventional vehicles over the 2020–2030 period and continues to decline through 2050. Higher projected capital costs for fuel cell vehicles and the assumed lower fuel efficiency of natural gas vehicles lead to higher costs per mile for these two technologies. This results in minimal penetration across all three modes in these results, although fuel cell vehicles do play some role in freight trucking. Replacement of conventional vehicles is also driven by the retirement of older vehicles, either at the end of their useful life or earlier via economic retirement. Economic retirement occurs in the ADAGE model if the cost to operate an existing vehicle is higher than the cost to operate and cover capital payments on a new vehicle. Economic retirements occur for some conventional and hybrid vehicles in the 2030–2050 time frame. Economic retirement of conventional passenger bus and freight trucks in the YesAFV version is evident after 2040 from conventional vehicle VMT declines that are larger than would occur from end-of-life retirements alone. The roles of hybrids and BEVs in the transition to AFVs vary by mode. For LDVs, the YesAFV results show hybrid vehicles serving as a “transition” technology from 2020 to 2040. These results show BEVs gaining greater adoption after 2030 and becoming the dominant technology by 2050. Hybrid vehicles play a smaller role in freight truck and passenger bus segments of the U.S. transportation sector. Instead, these modes transition more directly from conventional technology to battery electric technology. Our assumptions about technology costs and the flexibility of consumer preferences influence the timing of the transition to AFVs and highlight areas of uncertainty in this transition. As we discuss below, additional research should further explore the issue of the transition to AFVs. The availability of lower-cost LDVs in later modeled periods leads to increases in passenger VMT but decreases in freight truck VMT in the YesAFV version relative to the NoAFV version. The ADAGE structure allows for all global regions to have the same ability to purchase AFV technologies. The availability of efficient AFVs causes non-U.S. regions to rely more on domestic freight transportation production instead of imports from the United States. Increased freight truck VMT over time is met by a growing share of EVs rather than by hybrid vehicles. 4.1.2. U.S. fuel efficiency Absent alternative-fuel technologies, the vehicle fleet within each mode can only improve efficiency by investing in improvements for new conventional vehicles and then retiring older, less efficient vehicles. In addition to exogenous efficiency improvements for new vehicles over time, ADAGE allows for endogenous efficiency improvements for new conventional vehicles in response to the relative prices of capital and fuel, and the NoAFV version uses this ability to increase vehicle efficiencies in the REF case to some extent. With AFVs, the model outcomes for fleet fuel efficiency improvements parallel hybrid and BEV technology adoption across modes, leading to larger fuel efficiency improvements by 2050 for LDVs, freight trucks, and buses (see Fig. 7). More rapid EV adoption around 2040 produces visible inflection points in aggregate fuel efficiency increases in the YesAFV version. Concurrently, the introduction of light-duty AFVs reduces pressure on the transportation sector to invest in conventional vehicle efficiency after 2020. Under the assumptions used in the YesAFV version, the ADAGE model simulates that the least-cost solution is to concentrate investment capital in the relatively more efficient BEVs and hybrids. As a result, conventional vehicle fuel economy does not grow as rapidly after 2020 as it does in the NoAFV version. https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 18/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Download : Download high-res image (297KB) Download : Download full-size image Fig. 7. U.S. fleet-wide fuel economy for on-road transportation in the United States (Miles/MMBTU). These line graphs show fuel economy in miles per million metric British thermal units (MMBTU) for years 2020 through 2050. The graphs are separated by light duty, freight truck, and bus. The lines are separated by conventional and fleet average, with fleet average shown for the YesAFV and NoAFV versions. Both conventional and fleet average fuel economy are highest for light duty and average YesAFV is highest for most years for all vehicle types. Average, YesAFV has the greatest increasing slope over time for all vehicle types, especially light duty. For freight trucks and passenger buses, assumed differences in conventional and AFV costs are such that conventional vehicles remain the least-cost solution for most of the modeled period. Like LDVs, freight trucks and buses are subject to U.S. federal vehicle fuel efficiency standards (discussed in Section 3.1.1). The assumed efficiency standard targets for trucks and buses are much closer to the modeled future conventional technology efficiencies in these results. Endogenous changes in conventional freight truck and bus efficiency are therefore smaller than those for LDVs. 4.1.3. U.S. energy markets and GHG emissions In the NoAFV version, energy consumption in the U.S. transportation sector grows at a gradual rate of 0.5% per year, from 25.4 quads in 2020 to 29.9quads in 2050. Even without AFVs, LDV energy consumption declines as efficiency improvements more than offset the slight rise in light-duty VMT (see Fig. 8-a). The introduction of AFVs in the YesAFV version leads to a net increase in VMT across modes but a significant decrease in total energy consumption (see Fig. 8-a and -d). This result is driven by the marked rise in energy efficiency for all on-road modes over the 2020–2050 period. The rest of the U.S. transportation sector (air, water, rail, and other modes), where AFVs were not assumed to be an option in these scenarios, accounts for a growing fraction of total U.S. transportation energy demand and most U.S. transportation energy demand by 2050. Most of the energy demand from other U.S. transportation modes is served by fossil fuels. Including AFVs for these modes in the model could produce results with reduced energy use for these subsectors, as occurs for on-road vehicles in the results presented here, depending on the projected assumptions made about those AFVs. https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 19/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Download : Download high-res image (1MB) Download : Download full-size image Fig. 8. Level and change in transportation energy consumption (a, d), Electricity generation by technology (b, e), and GHG emissions by sector (c, f). This figure shows six bar graphs representing energy consumption, electricity generation, and GHG emissions for model years 2020 to 2050. Total energy consumption increases from one year to the next, with the greatest consumption occurring in transportation vehicles that are not light duty, freight, or bus for all years in the YesAFV version. For the NoAFV version, rest of transportation has the highest consumption in all years but 2020. Electricity generation by technology shows a decline in coal from 2020 to 2040 with a slight increase in 2050 for both YesAFV and NoAFV. Combined cycle gas takes up the greatest portion of the graph for all years expect for 2020, where conventional coal is the greatest, for both YesAFV and NoAFV versions. GHG emissions is highest for sectors not included in the model for all years and for both YesAFV and NoAFV versions. Emissions from fright truck is only present in the NoAFV version and shows an increase in emissions every year from 2020 to 2050. The expansion of EV technology also has a marked impact on U.S. electricity generation by 2050; in the YesAFV version, electricity generation in 2050 is estimated to be 28.8% higher than in the NoAFV version (see Fig. 8-b and e). ADAGE's cost projections for the U.S. electricity sector show electric generation capacity expansion that proportionally favors more efficient, lower GHG-emitting combined cycle natural gas plants and solar and wind power over coal-fired electricity generation. However, whereas coal is a proportionally smaller share of the 2050 energy mix than the 2020 energy mix in the YesAFV version, electricity generation from coal is slightly higher in these results than in the NoAFV version. In ADAGE, this can be interpreted as delayed retirement of preexisting coal https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 20/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect generation capacity rather than construction of new capacity. As electricity demand rises in the YesAFV version, so do electricity prices. Total U.S. GHG emissions in the NoAFV version rise by 8.2 (6970 to 7589 million metric tons of carbon dioxide [MMT CO2] equivalence [CO2-e]) from 2020 to 2050: most of the increase comes from outside the on-road transportation and electricity sectors. The introduction of AFVs slows down the increase of total U.S. GHG emissions by 0.7 percentage points (from 7042.14 to 7062.95 MMT CO2-e) during 2020–2050, where the largest reduction comes from light-duty, freight truck, and passenger bus transportation (1084to 117. MMT CO2-e by 2050; see Fig. 8-c and f). The net effect on total annual U.S. GHG emissions in 2050 is a 6.9% decrease from the NoAFV to the YesAFV version. U.S. electricity GHG emissions in 2050 are higher in the YesAFV version than in the NoAFV version (2107 MMT CO2-e in the YesAFV version versus 1672 MMT in the NoAFV version) owing to increases in transportation sector demand and moderated by relative declines in coal that reduce electricity sector emissions intensity. The higher energy efficiency of AFV technologies and declining electricity generation GHG emissions intensity over the time period modeled mitigate additional emissions associated with the increase in transportation electricity demand in the YesAFV results (see Fig. 8-c). In both versions, other transportation (especially air transportation) and other sectors (especially manufacturing and household demand for energy) contribute to rising emissions. 4.2. Alternative oil price cases In this section, we examine the impacts of different oil price paths on U.S. transportation and energy sector outcomes and net GHG emissions in the two ADAGE versions. As shown in Fig. 5, the HOP path from EIA has crude oil prices that are approximately double the prices in the REF case by 2050, and the LOP case has crude oil prices that are roughly half the REF case by 2050. The HOP case results in a 15% reduction in light-duty VMT in 2050 relative to the REF case in both the NoAFV and YesAFV versions of the model (Fig. 9). The comparable percentage reduction in VMT across different assumptions about the availability of AFVs suggests that lower light-duty VMT stem more from income effects on U.S. households under high oil prices than from substitution effects associated with higher VMT costs. Conventional LDVs and buses also phase out sooner in the HOP case than in the REF case. Hybrid AFVs play less of a transition technology role for LDVs with higher oil prices, as BEVs gain a comparative cost advantage over hybrids sooner with higher oil prices. Low oil prices induce proportionally opposite behavior; LDV hybrids serve longer as a transition technology (see Fig. A2 in Appendix A). Download : Download high-res image (359KB) Download : Download full-size image Fig. 9. Change in U.S. VMT in HOP case relative to REF case (Billion VMT). https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 21/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect This bar chart shows change in the high oil price (HOP) case relative to the reference (REF) case for vehicle miles traveled (VMT) for each model year (2010 to 2050). Net change overall is greater for light duty and freight truck than bus, with negative change for light duty and positive for freight truck. Freight truck VMT increases by around 14% with higher oil prices. The historical data on which ADAGE is built reveal that the United States has a relatively more energy-efficient manufacturing sector than most global competitors, such as China and Brazil (World Bank, 2012). Rising oil prices therefore tend to benefit the United States, improving competitiveness for the United States relative to foreign manufacturers and increasing U.S. manufacturing output (Fig. 10) and manufacturing demand for freight (as well as increasing GDP; see Fig. A4 in Appendix A). In the HOP case, U.S. net exports increase by $2–4 trillion between 2020 and 2050 compared to net exports over the same period in the REF case, leading to a higher freight VMT. Freight VMT is proportionally lower in the LOP case with lower U.S. manufacturing demand. Consistent with light-duty and bus technology composition, in the YesAFV version, the increased VMT for freight trucks is met by a larger share of EVs than by hybrid technology. Download : Download high-res image (284KB) Download : Download full-size image Fig. 10. Change in U.S. Economic output by sector in HOP case relative to REF case ($Billion). This bar graph shows a change in high oil price (HOP) relative to the reference (REF) case with stacked bars representing conventional and electric vehicles from 2020 to 2050. Difference in output from REF for manufacturing is the greatest among manufacturing, followed by light duty. In the early periods of the HOP case in the YesAFV version, most of the VMT reduction comes from conventional vehicles, which are not offset by AFVs. Minimal AFV adoption in early periods means fleet fuel efficiency improvements are limited to the endogenous efficiency response of new conventional vehicles, which are also being added at a slower rate as a result of lower VMT growth. In later periods in the HOP case, increased adoption of EVs improves fleet efficiency further relative to the REF case, but because this is primarily at the expense of hybrid vehicles, the fleet-wide efficiency improvements are modest. Conversely, relatively small decreases in U.S. fuel efficiency occur in the LOP case, with less endogenous efficiency improvements and slower AFV adoption, particularly for LDVs. Freight truck vehicles, whose VMT increase in the HOP case in the NoAFV and YesAFV versions and where EV adoption does not begin until the 2040s, show little efficiency gains with higher oil prices, until a slight increase in the early 2040s. Freight truck EV adoption is rapid in 2040–2050, leaving relatively little room for large compositional changes that would significantly change efficiency in either the LOP or HOP case. In both the NoAFV and YesAFV versions, U.S. transportation energy consumption declines by approximately 5 quads by 2050 in the HOP relative to the REF case, and about one-fifth of that decline is due to LDVs and the rest from the rest-of-transportation sector (Fig. 11). AFVs allow for slightly larger reductions in LDV energy consumption in 2020– https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 22/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect 2040 in the HOP case from earlier conventional vehicle retirement and EV adoption in the REF case. Reductions in U.S. transportation energy demand come from refined oil over the entire period, but this reduction is slightly offset by small increases in biofuels, which can be blended with oil for use in conventional and other vehicles. Download : Download high-res image (149KB) Download : Download full-size image Fig. 11. Change in U.S. Transportation energy consumption, HOP case relative to REF case (Quad BTU) This stacked bar graph shows differences in Quad BTU from the reference case (REF) comapred to the high oil price (HOP) case by transportation type. Most model years are included (2020 to 2050) and there is a seperation by YesAFV and NoAFV. Light duty and the rest of transportation sectors are negative, where freight truck is positive. Bus is negative for all years and versions expect for NoAFV in 2050. Net U.S. GHG emissions decrease under higher oil prices both with and without AFVs (Fig. 12), although the reduction relative to REF from LDVs is smaller in later years than earlier years with AFVs because most of the onroad vehicle inventory has already been electrified by 2050 (Fig. 6). Total U.S. GHG mitigation of approximately 960 MMT CO2-e in 2050 represents a decline of approximately 13% of total GHG emissions relative to REF for the United States from roughly doubling oil prices. Conversely, low oil prices lead to a 296–334 MMT CO2-e increase in emissions by mid-century relative to REF (Fig. A3 in Appendix A). ADAGE assumptions and structure project that roughly doubling oil prices in HOP relative to REF by 2050 leads to a percentage reduction in U.S. transportation sector GHG emissions of 34% in YesAFV and 18% in NoAFV. Roughly halving oil prices in LOP relative to REF leads to an increase in U.S. transportation sector GHG emissions of 35% in YesAFV case and 14% in NoAFV case. Download : Download high-res image (225KB) Download : Download full-size image Fig. 12. Change in U.S. GHG emissions by sector, HOP case relative to the REF case (MMT CO2-e). This bar graph shows differences in GHG emissions from the reference (REF) case comapred to the high oil price (HOP) by transportation sector. The overall net change is positive for 2020, then remains mostly netural for 2030 and 2040 before showing a negative change in 2050. 4.3. Sensitivity analyses We examined the sensitivity of our results to changes in the assumptions for two key components of our model, the fixed-factor substitution elasticity for alternative fuel vehicles and the structure of household consumption. We found that our core results were sensitive to the value of the fixed factor elasticity and largely insensitive to an alternative consumption structure. https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 23/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect For the transportation fixed factor elasticity, we conducted a set of two sensitivity analyses setting the fixed factor elasticities at 75% and 200% the current value. Model results are indeed sensitive to this parameter in the expected directions, i.e., higher elasticities lead to greater alternative fuel vehicle penetration and scrappage of conventional vehicles. There was one notable exception where elasticity results did not move in the expected direction: lightduty BEV adoption in the low oil price scenario declined in the scenario with the highest assumed elasticity. Instead, HEVs gained greater market share earlier in this scenario and remained cost competitive with BEVs under low assumed oil price conditions. BEVs still gained market share in later model periods but achieved a lower final market share due to crowding out from HEVs, relative to what we observe with lower elasticity assumptions. This result is due in part to the dynamics of the fixed factor and was not present in other oil price scenarios or transportation modes. Truck and bus AFV adoption appears more sensitive to the elasticity assumption. The relative costs of ICEs and BEVs are closer for trucks and buses than for other modes, making consumer propensity to adopt a more important parameter. In the 75% elasticity scenario, BEV trucks and buses achieve only slight adoption even in 2050, relative to the base case of complete AFV penetration by that year. Similarly, the 200% elasticity leads to a cessation of conventional vehicle production in the 2030s instead of 2040s. Appendix B contains figures summarizing the results of the fixed factor elasticity sensitivity analyses. We also explored an alternative specification for consumer demand for transportation. While demand systems have been an active area of research in the econometrics literature, their applications in economy-wide modeling are less prevalent. More work needs to be done to estimate alternative consumption structures with respect to transportation. Structures like the one we have adopted are used in other economy-wide models (e.g., EPPA). However, as we have emphasized in the paper, technologically detailed transportation sectors are not common to these models, perhaps weakening the motivation of past research to invest more effort in the specification of transportation consumption structures. As a sensitivity, we nested passenger transportation with housing under the notion that people substitute away from expensive housing toward more commuting (e.g., move farther out of the urban core) and freight with consumption goods purchases. Although changes in results were very modest, we believe that alternative consumption structures could be an area worthy of further research and investigation. The supplemental information includes the alternate consumption structure and sensitivity results for VMT by transportation mode and technology. 5. Discussion Inclusion of AFV technologies in the transportation sector in economic models is of increasing importance given their growing presence in global markets and the potential impacts they may have on energy consumption and GHG emissions. Our results suggest that including AFV technologies in a CGE model may alter the modeled energy and emissions outcomes; for example, adoption of BEVs may increase economy-wide electricity usage. Given the cost and performance characteristics of AFVs assumed in this analysis, including AFVs in ADAGE's on-road passenger and freight sectors produces significant changes in the projected level of U.S. transportation service demand, sector fuel efficiency, energy consumption, and GHG emissions. Cost and performance estimates for both battery packs and fuel cell stacks are changing frequently, and analyses seeking to characterize the current or likely future state of these markets should endeavor to use the most up-todate estimates available. The ADAGE model methodology presented in this paper provides a framework within which up-to-date vehicle cost and performance estimates can be used and continually updated for current analyses. However, even the most up-to-date projections of cost and performance carry uncertainty (e.g., regarding the pace of technological learning, the potential for technological breakthroughs). Modeled outcomes are likely to be sensitive to these uncertain assumptions, which suggests that uncertainty analysis and model sensitivity analysis are essential components of future work in this area. Future work could seek to characterize model parameter and scenario sensitivity using the ADAGE model or other CGE models. The impacts described in our results also vary depending on assumed future oil market conditions. Under our assumptions, the model results suggest that BEVs could capture a substantial and growing market share in the https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 24/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect coming decades and that hybrid technologies have the potential to play an important role in the next 10–15 years, particularly in model scenarios with lower oil prices. ADAGE estimates show higher oil prices speeding up the transition to EVs and shortening the intermediate transition role hybrid vehicles play. However, vehicles have complex and capital-intensive supply chains with high fixed costs, and these supply chain capital dynamics are not fully represented in ADAGE; thus, the results presented here should be viewed with caution from that perspective. While the future cost and performance characteristics of AFV technologies remain uncertain, it is clear from our results that exploration of potential future scenarios concerning energy consumption, GHG emissions, and economic output in CGE modeling frameworks would benefit from greater transportation sectoral detail and technological specificity. AFV technologies introduce new factors and dynamics to the transportation sector, such as new linkages with the electricity sector, which more aggregated representations of the sector cannot capture well. Leaving out AFV technologies limits the possibilities for changes in transportation sector and economy-wide energy consumption, emissions, and economic output; frameworks that do so may miss potential shifts in all of these outcomes in their scenario analyses. Our results demonstrate that these dynamics can and should be considered in CGE modeling frameworks, regardless of the specific cost, performance, or energy market or macroeconomic assumptions used to conduct a specific scenario analysis. 6. Conclusions The U.S. transportation sector is anticipated to undergo vast structural changes over the next several decades because of emerging market forces and evolving responses to the issue of climate change. CGE models, which examine the impacts of market forces on the whole economy, can be particularly useful in assessing emerging economic trends. To date, CGE models addressing GHG emissions have carried the most technological and subsector detail in the electricity sector portion of their models. Only a few CGE models have developed detailed representations of the transportation sector that can address structural changes likely to occur in this segment of the economy over the next several decades. Calibrating the ADAGE model to AEO 2018 oil price paths, we examined a case based on one assessment of projected future efficiencies and costs of AFVs. This analysis allowed for a demonstration of the novel transportation sector methods employed in this enhanced version of ADAGE. Different assumptions about vehicle efficiencies and costs lead to different model results for U.S. transportation sector outcomes and economy-wide outcomes. As a result, the major contribution of this paper is to demonstrate, and provide insight into, how transportation subsector and technological detail influences modeled economic and environmental outcomes in this framework. The results presented in this paper indicate modeled outcomes based on cost assumptions and model structure, not predictions of specific future outcomes. They provide a useful diagnostic tool for gaining insight on likely directions and relative magnitudes of market and environmental outcomes under different technology and cost assumptions. The ADAGE model represents the whole economy, and the transportation and electricity sector are integrated with one another. This feature makes the model well suited to estimate sectoral and economy-wide GHG impacts, as well as GDP impacts, which might result from a modeled shift in on-road vehicle fleet composition given a set of assumptions about technological options. Based on the assumptions used in this study, increased penetration of EVs results in significant reductions in U.S. transportation sector GHG emissions, increases in U.S. electricity sector GHG emissions, and reductions in economy-wide U.S. GHG emissions relative to results where ADAGE did not include AFVs as an option. As expected, simulations with higher oil prices lead to more rapid penetration of AFVs, and lower oil prices lead to slower penetration of AFVs. This work shows the significance of including transportation technology representation in an economy-wide model and provides an example of how this detail was applied to a particular CGE, ADAGE. However, the limitations to the approach described here could be improved in ADAGE or other CGEs. Extending subsector and technological detail introduced for on-road vehicles, as undertaken in this effort, throughout the whole transportation sector is a valuable next step in identifying future market and environmental outcomes for the transportation sector overall. Transportation modes in which technological detail could be added include air, rail, and marine. Each of these https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 25/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect transportation modes will have a different set of technologies with different performance and cost characteristics that would need to be considered in developing detailed, technological assessments. In addition, developing explicit representation of hydrogen in a CGE model could allow for more detailed understanding of potential impacts of fuel cell vehicles. For both AFVs already incorporated in ADAGE and for these potential new technology options, there may be important network externalities that affect estimated technology penetration. In the current study, we utilize fixed factors to account for such effects, but a more detailed characterization of technology adoption may be a fruitful area for future research. Finally, analyzing criteria air pollutants in a CGE model would allow key assessments of multipollutant effects of air quality and climate change simultaneously from alternative scenarios. The transportation sector technological detail presented in this paper, as well as these areas for potential future research, could help make CGE models more useful in understanding impacts of future shifts in the transportation sector. Role of the funding source The work conducted for this article was done under support received through U.S. Environmental Protection Agency (EPA) contracts EP-C-16-021 and 68HERH19D0030. Three of our authors are employed by EPA and administered the project supporting its completion. EPA authors' contributions are documented in the CRediT author statement. CRediT authorship contribution statement Yongxia Cai: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Validation, Visualization, Writing – original draft, Writing – review & editing. Jared Woollacott: Formal analysis, Investigation, Methodology, Project administration, Supervision, Writing – review & editing. Robert H. Beach: Conceptualization, Formal analysis, Investigation, Methodology, Writing – original draft, Writing – review & editing. Lauren E. Rafelski: Conceptualization, Funding acquisition, Methodology, Project administration, Supervision, Validation, Writing – review & editing. Christopher Ramig: Conceptualization, Funding acquisition, Methodology, Validation, Writing – review & editing. Michael Shelby: Conceptualization, Methodology, Validation, Writing – review & editing. Declaration of Competing Interest None. Acknowledgments The views expressed in this article are those of the authors and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency. The authors gratefully acknowledge Page Kyle from Pacific Northwest National Laboratory for providing us with transportation related data, Avery Tilley from RTI for data visualization and literature research, and Jim McFarland and Gloria Helfand from the U.S. Environmental Protection Agency for providing helpful comments on the paper. Appendix A Table A1. Fuel economy for all on-road new vehicles in the United States from 2010 to 2050 (Miles/million British thermal units [MMBTU]). 2010 2015 2020 2025 2030 2035 2040 2045 2050 Conventional 204 210 231 291 292 292 290 288 284 Natural gas 194 198 222 284 287 287 287 286 282 Battery 630 646 714 775 777 782 785 785 782 Light-duty (miles/MMBTU) https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 26/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect 2010 2015 2020 2025 2030 2035 2040 2045 2050 Hybrid 338 348 383 463 463 461 458 453 446 Fuel cell 461 467 474 479 485 492 499 507 515 Freight truck (miles/MMBTU) Conventional 69 74 77 80 83 85 86 87 88 Natural gas 62 67 69 72 75 77 77 78 80 Battery 207 222 231 240 249 255 259 262 265 Hybrid 86 92 96 100 104 106 108 109 110 Fuel cell 138 148 154 160 166 170 172 175 177 Conventional 54 55 62 66 68 72 75 79 83 Natural gas 49 49 55 59 61 64 68 71 75 Battery 214 220 246 264 273 287 301 316 333 Hybrid 81 82 92 99 102 107 113 119 124 Fuel Cell 107 110 123 132 136 143 151 158 166 Bus (Miles/MMBTU) Table A2. Passenger vehicle ownership growth trend by ADAGE regions (1 in 2010). 2010 2015 2020 2025 2030 2035 2040 2045 2050 United States 1 1.01 1.06 1.10 1.14 1.18 1.21 1.24 1.27 Brazil 1 1.20 1.42 1.63 1.83 2.00 2.16 2.30 2.42 China 1 1.40 1.95 2.47 2.96 3.41 3.81 4.16 4.44 European Union 1 1.05 1.09 1.13 1.16 1.19 1.21 1.23 1.24 Rest of Latin America 1 1.31 1.69 2.09 2.47 2.85 3.22 3.57 3.89 Rest of Asia 1 1.26 1.56 1.86 2.15 2.44 2.71 2.97 3.20 Africa 1 1.70 2.85 4.15 5.61 7.24 9.05 11.01 13.11 Rest of World 1 1.24 1.48 1.71 1.9 2.14 2.35 2.55 2.73 https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 27/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Download : Download high-res image (411KB) Download : Download full-size image Fig. A1. Comparison of Key Results in Two Versions of the Model (NoAFV: Version with eight modes of transportation and no alternative-fuel technologies; Agg: Version with two modes of transportation with light-duty and aggregated transportation from the other seven modes and no alternative-fuel technologies) in the REF Scenario: a. U.S. Transportation Energy Consumption by Mode in (Quad BTU); b. U.S. Electricity Generation by Generation Technology (Quad BTU); c. U.S. GHG Emissions by Sector (MMT CO2-e). This figure has three bar graphs showing two versions of the model (NoAFV and Agg) for the reference (REF) case for years 2020 to 2050. Transportation vehicles that are not light duty, freight, or bus have the most energy consumption in all years and case expect for NoAFV 2020 where light duty consumes the most. Fright truck and bus only appear in the NoAFV case. Electricity generation is highest for combined cycle gas and conventional coal, until 2050 where the highest is combine cycle gas and solar. Most GHG emissions are the result of the other sectors category for all years modeled. https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 28/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Download : Download high-res image (243KB) Download : Download full-size image Fig. A2. Change in U.S. vehicle miles traveled in LOP case relative to REF case (billion VMT). This figure shows the difference in vehicle miles traveled (VMT) from the reference (REF) case compared to the low oil price (LOP) case from 2020 to 2050. Light duty shows a positive net change, freight truck shows a negative net change, and bus has a relatively neutral net change. Download : Download high-res image (139KB) Download : Download full-size image Fig. A3. Change in U.S. GHG emissions by sector, LOP case relative to the REF case (MMT CO2-e). This bar graph shows the low oil price (LOP) case relative to the reference (REF) case in change in GHG emissions by sector. The overall net change is negative for 2020 then remains positive for 2030 through 2050. Light duty, other transportation, bus, electricity production, and freight truck are always positive. https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 29/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Download : Download high-res image (271KB) Download : Download full-size image Fig. A4. GDP growth trend by region and scenario (0 in 2010) (a) and change in GDP in YesAFV from NoAFV (b) ($Billion). This figure has four line graphs showing GDP growth tends by oil price case and change in GDP from NoFAV version. GDP trends up in all cases, both in the U.S. and in other countries, for all years. The high oil price (HOP) case shows the greatest growth in GDP in the U.S. but the least in other countries, where the low oil price (LOP) case shows the greatest growth. Change in GDP from the NoAFV version increase in both the U.S. and Non-U.S. countries for all years, with a greater initial increase in Non-U.S. countries. Appendix B Download : Download high-res image (322KB) Download : Download full-size image Fig. B1. Light-duty passenger transportation by technology, fixed factor elasticity, and scenario (billion VMT). This figure provides a three-by-three stacked bar graphs. The height of each column is the total vehicle miles traveled in a time period. The components of each bar represent the different vehicle technologies. Each row is a different scenario, low oil price, reference, and high oil price from top to bottom. The first column is our 75 % https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 30/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect elasticity, the second is our reference results, and the third is our two-times elasticity sensitivity results. Total VMT is largely unchanged across sensitivity and reference results, but the technology mix varies with generally more non-ICE vehicle penetration for higher elasticity values. Download : Download high-res image (300KB) Download : Download full-size image Fig. B2. Road freight transportation by technology, fixed factor elasticity, and scenario (billion VMT). This figure provides a three-by-three stacked bar graphs. The height of each column is the total vehicle miles traveled in a time period. The components of each bar represent the different vehicle technologies. Each row is a different scenario, low oil price, reference, and high oil price from top to bottom. The first column is our 75 % elasticity, the second is our reference results, and the third is our two-times elasticity sensitivity results. Total VMT is largely unchanged across sensitivity and reference results, but the technology mix varies with generally more non-ICE vehicle penetration for higher elasticity values. Download : Download high-res image (298KB) Download : Download full-size image Fig. B3. Bus passenger transportation by technology, fixed factor elasticity, and scenario (billion VMT). https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 31/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect This figure provides a three-by-three stacked bar graphs. The height of each column is the total vehicle miles traveled in a time period. The components of each bar represent the different vehicle technologies. Each row is a different scenario, low oil price, reference, and high oil price from top to bottom. The first column is our 75 % elasticity, the second is our reference results, and the third is our two-times elasticity sensitivity results. Total VMT is largely unchanged across sensitivity and reference results, but the technology mix varies with generally more non-ICE vehicle penetration for higher elasticity values. Appendix C Download : Download high-res image (161KB) Download : Download full-size image Fig. C1. Alternative consumption structure. This figure depicts the alternative structure for household demand used for our sensitivity analyses by displaying its inputs and connecting them with lines to indicate how they are combined in the household utility function. Each vertex includes inputs whose substitution is parameterized by the elasticity displayed for that vertex. https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 32/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect Download : Download high-res image (266KB) Download : Download full-size image Fig. C2. Light-duty vehicle transportation by technology, consumption structure, and scenario (billion VMT). This figure provides a three-by-two stacked bar graphs. The height of each column is the total vehicle miles traveled in a time period. The components of each bar represent the different vehicle technologies. Each row is a different scenario, low oil price, reference, and high oil price from top to bottom. The first column is our reference results and the second is our results with the alternative transportation structure. Total VMT and technology mix is largely unchanged across sensitivity and reference results. Download : Download high-res image (237KB) Download : Download full-size image Fig. C3. Road freight vehicle transportation by technology, consumption structure, and scenario (billion VMT). This figure provides a three-by-two stacked bar graphs. The height of each column is the total vehicle miles traveled in a time period. The components of each bar represent the different vehicle technologies. Each row is a different scenario, low oil price, reference, and high oil price from top to bottom. The first column is our reference results and https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 33/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect the second is our results with the alternative transportation structure. Total VMT and technology mix is largely unchanged across sensitivity and reference results. Download : Download high-res image (246KB) Download : Download full-size image Fig. C4. Bus vehicle transportation by technology, consumption structure, and scenario (billion VMT). This figure provides a three-by-two stacked bar graphs. The height of each column is the total vehicle miles traveled in a time period. The components of each bar represent the different vehicle technologies. Each row is a different scenario, low oil price, reference, and high oil price from top to bottom. The first column is our reference results and the second is our results with the alternative transportation structure. Total VMT and technology mix is largely unchanged across sensitivity and reference results. Recommended articles Data availability Data used in this paper were from ADAGE simulation results, which are available on the following Zenodo site: (adding address when accepted). 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Constant elasticity of substitution (CES) https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 45/46 2023/5/12 11:11 Insights from adding transportation sector detail into an economy-wide model: The case of the ADAGE CGE model - ScienceDirect A functional form used for modeling production and consumption behavior that posits a constant percent change in the quantity ratios of two inputs relative to price ratios. Dynamic Economic models that include change over time. Gross domestic product (GDP) The monetary value of total income or expenditure (including savings and investment) within a country. Intertemporal Dynamic models that include responsiveness to future modeled outcomes. Leontief production function A production function with no substitution between inputs. Recursive-dynamic CGE models that assume behavior depends only on current and past states of the economy and can be solved sequentially. Sectoral heterogeneity Differences in input requirements and substitution responses across sectors. 1 We focus here on national and global energy-focused models incorporating transportation modules. However, there are a broader array of CGE models that have been applied to analyses of transportation issues, including models that are primarily focused on urban, regional, economic development and related questions rather than energy and environmental economics (Robson, Wijayaratna, and Dixit, 2018). 2 In this paper, costs and prices are presented in 2010 dollars. 3 The crude oil price in the LOP case starts at $28/barrel in 2020 and rises slowly to $46/barrel in 2050. The crude oil price in the HOP case starts at $109/barrel in 2020 and rises to $205/barrel by 2050. We continued using the 2018 AEO projections for the LOP and HOP scenarios as well with the same rationale. Neither the AEO projections nor the ADAGE model includes the impact of countries' commitments under the Paris Agreement that are not already enacted in law. View Abstract © 2023 Published by Elsevier B.V. Copyright © 2023 Elsevier B.V. or its licensors or contributors. ScienceDirect® is a registered trademark of Elsevier B.V. https://www.sciencedirect.com/science/article/pii/S0140988323002086#f0005 46/46