Energy transition in sustainable transport: concepts, policies, and methodologies

<jats:title>Abstract</jats:title><jats:p>The growth in population, economic expansion, and urban dynamism has collectively driven a surge in the use of public and private transport, resulting in increased energy consumption in this sector. Consequently, the transport sector requires an energy transition to meet mobility demands, foster economic growth, and achieve emission reduction. The main objective of this article is to systematically review the literature on energy transition in transportation, categorizing research, identifying barriers, and providing analysis to guide future steps, with a special focus on developing countries. The methodology used in this study follows a sequence for a systematic review based on an evidence-informed approach and specific guidelines for systematic reviews, exploring the concepts, methodologies, and policies within the context of the energy transition, considering transport modes and geographical scope. The findings indicate that electricity is the predominant energy source in this transition, although its prevalence varies by transport mode. Biofuels present an alternative, primarily contributing to emission reduction associated with fossil fuel use. Natural gas emerges as a cost-effective option for heavy transport, while hydrogen represents another alternative, with the challenge of developing recharging infrastructure. Determinants of this transition include recharging infrastructure, tax and nontax incentives, public policies, the generation of electric power from renewable sources, and the management of battery life cycles from mineral extraction to disposal.</jats:p>

section_content: According to the United Nations (UN), even though urban areas comprise just 3% of the Earth's surface, they house more than half of the world's population and are responsible for 70% of energy consumption and 75% of carbon emissions. All of this is a direct result of urbanization (Ruggieri et al. 2021). Urbanization leads to an increased demand for transport services across all modes (Breyer et al. 2019), resulting in higher energy consumption and CO2 emissions (Mohsin et al. 2019). Globally, the transport sector emitted approximately 8. 5 gigatons of CO2 in 2019 and over 7 gigatons in 2020 (International Energy Agency 2021). 

Consequently, it is imperative to assess alternative measures for optimizing energy usage, diversifying fuel options, and reducing CO2 emissions (Haase et al. 2022 ). Transport plays a signi cant role in the emission reduction strategies proposed by countries, especially considering the recommendations of the Intergovernmental Panel on Climate Change. To achieve the scenario of limiting global warming to 1. 5°C and avoid reaching irreparable levels, immediate actions and profound transformations are necessary (IPCC 2021). Zero-and low-emission vehicle technologies must assume a more prominent role in reducing our dependence on fossil fuels, with electricity, hydrogen, and biofuels taking the lead (Raslavičius et In line with the aforementioned, the energy transition in transport is seen as a viable alternative to achieve decarbonization within this sector (Raslavičius et Given its complexity, the literature approaches the energy transition in the transport sector from diverse angles. Some countries prioritize the energy transition as an alternative to achieving harmony within the transport sector (Nordelöf et al. 2014; Fiori et al. 2018 ; Dalala et al. 2020 ; Ku et al. 2021; Stecuła et al. 2022). Consequently, the literature has accumulated a substantial body of knowledge in this eld, leading to the implementation of various research methodologies and policies aimed at analyzing and promoting this transition. This is why gaining a comprehensive understanding of the current state of the energy transition in the transport sector presents a formidable challenge. 

Therefore, it is necessary to search, consolidate, synthesize, and know the conceptual and methodological states of the energy transition in transport. Knowing the conceptual and methodologies through which the literature has studied the energy transition in transport is crucial to identifying the energy transition state and the research conducted in this area. This study focuses on the above areas by systematically reviewing existing literature on the energy transition in transport. This study aims to know the conceptual and methodological states, categorize the research worldwide in general topics, identify different barriers and challenges, and provide an analysis that allows the reader to establish the next step and future implications. Another contribution of this document is to offer a systematic guide on how to approach an energy transition in the transport sector within developing countries undergoing rapid urbanization. 

Therefore, this study developed around three main Research Questions:

1. What are the conceptual states of the energy transition in transport?

2. What methodologies have been used to analyze the energy transition in the transport sector?
section_name: Introduction

section_content: This work is structured as follows: Section 2 outlines the research methods utilized in this study. In Section 3, we present the results of both the bibliometric and content analyses. Section 4 delves into the discussion of our responses to the proposed research questions. The rst research question is addressed in Section 4. 1, the second in Section 4. 2, and the third in Section 4. 3. Finally, Section 5 encapsulates the conclusions drawn by the authors.
section_name: What policies have been implemented to encourage energy transition in transport?

section_content: For the development of this paper, a systematic literature review was implemented. It was carried out in two parts: data collection and analysis, as shown in the following.
section_name: Materials and methods

section_content: A search was conducted in the Web of Science database (ISI Web of Knowledge) for the bibliographic review on January 15, 2023. The terms used in the equation were selected to answer the three research questions: Energy transition and sustainable transport. 

The search equation was TOPIC: (Energy transition) AND TOPIC: (Sustainable transport). 

From the search, 646 results were obtained. In the next step, titles and abstracts were assessed, and 57 documents were identi ed as outside the topic. Criteria were established to select the articles correlating most with the research topic: First, studies with a publication date after 2014 and December 31, 2022, were selected. The subsequent step involves reviewing the remaining 561 records, applying lters to exclude items that do not align with the investigation's main themes, such as energy transition and sustainable transport. The most relevant documents were then selected, resulting in a nal set of 127 articles, as illustrated in Fig. 1. It is pertinent to highlight that since the words "Energy Transition"

were part of the search equation, many documents focused on renewable energy were obtained, this situation generated many results that were not related to the Transport sector, so they were excluded in lling out the matrix.
section_name: Data collection

section_content: For data analysis, we constructed a matrix that included the following elements from each reference: the reference itself, the primary subject related to energy transition in transport, the author's interpretation of the energy transition concept in land transport, the methodology or methodologies used in the reference, key ndings, geographical scope, transport mode, relation to energy sources, connection with the broader energy transition, and its relationship with land transport. The information extracted from this matrix helped identify the main concepts related to energy transition, the methodologies applied in researching energy transition within the transport sector, and globally implemented policies aimed at advancing this transition.
section_name: Data analysis

section_content: According to the de ned inclusion criteria, a total of 127 papers were published in 38 different academic journals. Table 1 highlights the ten sources that contributed the most to these publications. Notably, Renewable and Sustainable Energy Reviews took the lead with 12 of the 127 papers. The number of publications on the subject has had a particular behavior, growing until 2018 and decreasing as of this year since the rst publication in 2014 and the last on December 31, 2022, as shown in Fig. 2. 

The reviewed documents' geographical scope made it possible to highlight the regions in which more research has been conducted on energy transition in transport. These documents highlight the actions, results, strengths, and barriers in their countries or regions: 33% of the articles didn't mention a speci c country or region without referring to a country or region, 9% referred to Europe, highlighting Germany, Spain, and Portugal, 7% corresponded to Asia, highlighting China, Japan, Singapore, and the Philippines, 3% corresponded to North America, and 5% corresponded to Latin America, featuring Brazil and Argentina. Finally, the remaining 42% corresponded to the Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden) and the Netherlands, showing that it is a region focused on research and investment in the energy transition in transport, as shown in Fig. 3. 

Concerning modes of transport, 29% of the documents consider various modes (rail, sea, and road) and did not speci cally highlight anyone. Of them, 67% referred to road mode, including private transport (94%), freight Transport (5%), and passenger transport (1%). Finally, the maritime mode had a share of 3% in all documents reviewed; one of the unique positions is promoting alternative fuels that reduce maritime transport's environmental and climatic impacts in the short, medium, and long-term (Hansson et al. 2019). Maritime transport has access to a range of energy sources, such as lique ed natural gas (LNG), lique ed biogas (LBG), methanol produced from natural gas, renewable methanol, hydrogen for fuel cells generated from natural gas or through electrolysis using renewable electricity, hydrotreated vegetable oil, and heavy fuel oil (Hansson et al. 2019). 

Some strategies to make these technologies viable for shipping include a better understanding of marine fuel supply chains and the implications of fuel switching, avoiding cargo displacement, establishing better emission monitoring strategies and public procurement mechanisms, and promoting policy instruments (Bach et al. 2020; Bonou et al. 2020). 

That shows the predominance of road transport in research exercises on energy transition in transport. Three documents referred brie y to air transport, indicating signi cant gaps for energy transition between the transport modes.
section_name: Results

section_content: Conceptual states of the energy transition in transport. 

We identi ed a predominance of four general topics. Of 127 articles, 57% have e-mobility as their main topic, 20% other energies, 13% public policy, and 5% biofuels. To address the initial question, three topics will be discussed. The aspects concerning public policy will be further developed later to respond to the third research question in the section "Policies to encourage energy transition in transport".
section_name: Discussion

section_content: The interest of the different authors in the promotion of electrical technologies and the environmental bene t with which they related was identi ed, which made it possible to show that it is the central vision of the nation's investigating energy transition in transport. 

Migration to hybrid EVs (HEVs), plug-in HEVs (PHEV), battery-EVs (BEVs), and fuel cell vehicles is a viable and successful alternative in the energy transition (Mersky et According to (Greim et al. 2020 ), the current production trend suggests a short and medium-term balance between the supply and demand for lithium. Conversely, the long-term sustainability of the transport sector is under threat due to the increasing demand for electric vehicles (BEV, PHEV, and HEV). 

Supply limitations could become apparent from 2030, according to current recycling rates corresponding to less than 1%, preventing the deployment of BEVs and increasing the emissions from operating vehicles in 2050 (Watari et al. 2019 ). However, increasing the recycling rate to 80% could markedly alleviate constraints on the shift towards battery electric vehicles (BEVs), all without the need for a primary supply from natural deposits that far exceeds historical expansion rates (Watari et al. 2019 ). 

Therefore, a balanced supply and demand for lithium depend on well-established recycling systems (Greim et al. 2020 ). 

Nevertheless, if the quality of lithium recovered from recycling electric vehicle batteries is not high enough to support reprocessing in battery production, it could lead to a substantial oversupply of secondary materials (Ziemann et al. 2018 ). Here, the application of secondary lithium would be con ned to other sectors, limiting the potential resource savings (Ziemann et al. 2018). 

A united global endeavor is required to enforce well-established recycling systems, enhance transport services, and improve battery performance, aiming to reduce the sector's lithium intensity while increasing efforts to explore alternative uses for lithium (Greim et al. 2020 ). 

Another alternative for lithium exploitation can be to develop novel concepts such as V2G (Zubi et al. 2018 ). Vehicle-to-grid (V2G) describes a system in which energy can be used for self-consumption or sold to the electricity grid by the driver of an EV or PHEV when connected to the grid and not used to power the vehicle. It allows exchanging energy between the vehicle and the electrical grid (Paiho et al. 2018a ). V2G technology can be divided into two categories: unidirectional and bidirectional, depending on the direction of power ow between the power grid and the electric vehicle. In unidirectional V2G, the communication between the power grid operator and the EV is employed to regulate the charging rate of each EV individually (Tan et al. 2016 ). 

Optimizing EV charging with V2G technology has the potential to reduce the need for signi cant investments in peak power capacity in all regions. It can also mitigate the reliance on short-term and long-term storage technologies other than EV batteries, such as stationery and hydrogen storage. Furthermore, V2G-optimized charging can substantially boost solar and wind power generation in speci c regions, addressing the issue of renewable energy intermittency (Taljegard et al. 2019b ). 

Additionally, a V2G charging strategy for passenger EVs helps to atten the net charge curve and, most signi cantly, diminishes the demand for maximum power capacity in the electrical system (Taljegard et al. 2019a; Kester et al. 2019 ). 

As outlined by (Paiho et al. 2018b ), in their 2018 study, delivering network services can be quite challenging due to the unpredictable nature of EV storage, and V2G technology is closely following suit in terms of complexity. The research also suggests that, especially as the adoption of electric vehicles increases, smart charging is anticipated to be a more critical source of exibility compared to V2G. 

Nevertheless, it's expected that V2G will continue to evolve independently with time (Kester et al. 2018a ). 

In addition, the authors recommend a set of measures to anticipate the barriers identi ed when promoting electric mobility ( Use EVs only for short-distance Transport between cities. 

Promoting transport-as-a-service and car-sharing has enormous potential to reduce the demand for energy and materials for road transport. 

In conclusion, the literature review allows us to highlight a series of bene ts related to electric mobility, such as the reduction of emissions since it does not involve the combustion of energy if we only consider a Tank to Wheel analysis (
section_name: E-mobility

section_content: ). Lastly, the development of value chains that allow the recovery of the lithium used in the batteries of electric vehicles will minimize the impact on mining exploitation, which will postpone the reserves of the resource (Ziemann et al. 2018 ). 

E-mobility is a promising alternative to decarbonize the Transport sector. Still, it must be developed jointly with public policy actions that promote clean energy, active mobility, and the massi cation of public transport, thus achieving diverse, environmentally friendly, sustainable, and meeting the needs of people. 

Other energies for energy transition Another alternative is synthetic fuels. First, we begin by examining the distinctions in the terminology used for various fuels. Renewable fuels encompass those produced using sustainable resources, which include a variety of fuels derived from biomass and other renewable energy processes (Ridjan et al. 2016a ). On the other hand, alternative fuels are de ned as substitutes for gasoline because they can be manufactured without restrictions on the type of raw material, allowing them to be sourced from either renewable or fossil resources (Ridjan et al. 2016a ). However, it's worth noting that the term 'synthetic fuel' is often used in a generic manner in most literature without speci c reference to the fuel production process or differentiation between synthetic fuels derived from either fossil or renewable sources (Ridjan
section_name: 2022

section_content: There is also talk of electro-fuels produced from CO 2 and water and need electricity (Brynolf et al. 2018 ). 

These fuels have two factors affecting production costs: electrolyzer and electricity prices (Brynolf et al. 2018). Therefore, the costs of the distribution, propulsion, and storage systems are the relevant factors determining whether electro-fuels will be the fuel of the future compared to other fuels. 

Many alternative fuels, including electricity and hydrogen, require extensive adjustments to the recharging infrastructure due to their technical properties being incompatible with the existing infrastructure (Ridjan et al. 2016b ). To avoid the need for a complete transformation of the current transport infrastructure, it is essential to utilize fuels that can operate within the existing framework. This approach is considered a way for these fuels to gain prominence during the energy transition, as suggested by (Ridjan et Although challenges around cost and performance persist, considerable improvements are required to make hydrogen competitive. In the medium term, the hydrogen alternative in the transport sector no longer seems unrealistic, fully justifying the growing interest and policy support for these technologies globally (Staffell et al. 2019 ). According to (Kovač et al. 2021), it is clear that without incorporating hydrogen technology in energy transition strategies, there will not be enough potential to immerse in a carbon-neutral future fully; this also applies to the transport sector. 

Finally, according to (Lorenzi and Baptista 2018), the massive introduction of gas vehicles could reduce emissions and the current dependence on conventional fuels, such as gasoline and diesel. This energy source has a considerable opportunity in the heavy vehicle (cargo transport) segment, representing a signi cant part of fossil fuel consumption (Brauers 2022). NGV also has some problems, such as the space required for storage, autonomy, and transport management (Cadavid and Fr 2016). 

The primary obstacles to the development of NGVs, particularly in countries without natural gas reserves, are the shortage of natural gas supply and its higher price compared to gasoline. To further stimulate the growth of NGVs, as proposed by (Wang et al. 2015), the following strategies can be implemented: (1) Enhance the natural gas supply infrastructure, (2) reduce the price of natural gas in comparison to gasoline and diesel, (3) prioritize middle-income cities and regions where the establishment of natural gas service stations is uncomplicated, and (4) promote the adoption of NGVs within the private sector.
section_name: et al. 2016a).

section_content: Biofuels are among the alternative energy sources that can be used for an energy transition. If biofuel production and use are employed in the transport sector, many agricultural regions can bene t from the energy transition (Anderson 2015). Biofuels can be of four generations: 1G (vegetable oils and animal fats), 2G (inedible lignocellulosic biofuels based on biomass), 3G (biofuels based on macro and microalgae), and 4G (algae and genetically modi ed waste) (Darda et al. 2019 ). 

According to (Darda et al. 2019), the question of which generation of biofuel aligns best with sustainability criteria remains unanswered. Both 1G and 2G biofuels serve as fundamental components in the realm of transport fuels (Darda et al. 2019 ). However, 1G biofuels fall short of meeting sustainability standards due to con icts stemming from increased food demand, as noted by the same authors. On the other hand, 2G biofuels, being more abundant, are globally endorsed as a solution to sustainability challenges within the transport sector and as a response to criticisms directed at rstgeneration biofuels. Nonetheless, some 2G biofuels exhibit issues such as low-carbon and nitrogen emissions, failing to establish a sustainable balance between food, energy, and water, as observed in their research (Darda et 3G biofuels based on algae could be the future in the transport sector, primarily in road transport and aviation, but it has some drawbacks (Darda et al. 2019). Microalgae is an aquatic crop with a promising future for supplying biofuels in the short and medium term, but its cultivation is considered ine cient and demands signi cant energy (Darda et al. 2019). 

Finally, 4G biofuels, primarily based on industrial, agricultural, and municipal waste, aim to accelerate the circular economy (Darda et al. 2019 ). However, they entail expensive and energy-intensive processing methods (Darda et al. 2019 ). 

According to (Anderson 2015), bioethanol often increases nitrogen oxide (NOx) emissions. Likewise, using fuels blended with biodiesel typically increases NOx emissions and decreases particulate matter emissions (Anderson 2015). It is important to observe that the pricing, perceptions of quality, potential engine damage, and environmental attitudes collectively impact the self-reported willingness to opt for these biofuels (Andersson et al. 2020 ). 

In the future, technologies should minimize the adverse effects of biofuels on vehicle emissions. However, this will require properly designed vehicles for consuming speci c biofuels or biofuel blends and high investments in infrastructure ( Lastly, the large-scale production of biofuels demands signi cant amounts of biological resources, a consideration that becomes crucial given the nite capacity of ecosystems to supply natural raw materials. Hence, electric vehicles (BEVs) and fuel cells stand out as sustainable means for transporting passengers and goods (Anderson 2015). 

Methodologies for the study of the energy transition in transport. 

Within the theme of energy transition in the transport sector, the authors' approaches are varied, and they also use different methodologies to address the research carried out. The results are displayed in Table 3. Literature reviews, surveys, interviews, and focus groups are used for gathering information. System Dynamics and modeling software such as LEAM or ANSWER stand out among the modeling methodologies. Various methods are applied in the literature to analyze the penetration of zero and low-emission technologies. According to (Jochem et al. 2018b), no dominant methodology exists, but each method has advantages and disadvantages in speci c elds. Some advantages are that market behavior can be explained by aggregating individual decisions made from discrete choice models, a desirable combination of theory and empirical basis can be counted on, and different actors can be considered. 

Although the purpose of implementing these methodologies was to analyze the energy transition, none of the documents reviewed presented evaluations of actions or policies implemented or to be implemented, a consideration also a rmed by (Zhao et al. 2020 ). According to (Bjerkan et al. 2016 ), the low explanatory power of the models presented in the literature indicates the need for better data and information that demonstrates the complexity of the factors surrounding the adoption of zero and lowemission technologies and the role of the different public policies. 

Policies to encourage energy transition in transport. 

Transformations towards sustainable development are seen as a political challenge. According to the authors, a series of public policies are required that promote sustainable transport and active mobility, speci cally using electric and human-powered vehicles (Lin et al. 2018; Roberts 2020; D'Adamo et al.
section_name: Biofuels

section_content: According to research by (Zimm 2021 ), the primary focus of most studies lies in catering to policymakers, offering them scienti c insights to inform their decision-making processes. However, there is a distinct need for an analysis of policies and their origins, with an emphasis on the diverse sources of transformative policies, going beyond the conventional notion that such policies solely arise from political mandates or external pressures, be it from the public or industry. Supportive policies, as a critical and in uential tool, play a pivotal role in guiding and expediting the widespread adoption of electric vehicles. It is worth noting that policymakers are tasked with addressing a wide range of national strategic objectives when allocating their limited public resources. 

Furthermore, it is imperative to introduce incentives as part of public policy to stimulate the adoption of electric vehicles. As indicated by the extant literature, various incentives can be implemented, including measures like reduced purchase taxes, exemption from value-added tax (VAT), toll fee waivers, and privileges like access to designated bus lanes. These incentives can be categorized into two primary groups: nancial incentives and non-nancial incentives, or they can take alternative forms, such as support for charging infrastructure, raising consumer awareness, or the imposition of mobility restrictions, as outlined in studies conducted by (Lévay et A multidimensional governance approach must be forti ed that guarantees lasting incentives and mechanisms to mobilize investment funds for fast charging along public roads and home charging. Furthermore, more oriented governance is needed to reduce the information barriers and generate knowledge for consumers and companies to promote incentives. It must also support structural and technological changes within the automotive industry (Nilsson and Nykvist 2016). 

Furthermore, it is necessary to establish vehicle labels that allow knowing the vehicles traveling with more sustainable energy and their cost so that buyers can make better decisions (Brazil et al. 2019). 

Another policy action expressed in the revised documents is the promotion of public transport. This requires investments in infrastructure, reduction in the cost of public transport, taxes on the purchase of fuel vehicles, better roads, vehicle restrictions, and parking reforms (Salvucci et According to Zimm (2021), the form of government and the level of federalism do not exert a signi cant in uence on the timing of the adoption of new technologies. Recent history provides ample evidence of this, with electric vehicles rapidly gaining popularity in countries as diverse as Norway, France, China, and the United States. However, the probability of electric vehicle adoption increases over time, as expected. This increase can be attributed to global technological learning, with a signi cant contribution from the industry. Over time, cumulative production grows, resulting in improved performance, reduced costs, and greater availability of charging infrastructure. This progression is clearly evident in the adoption sequence, where countries with initially lower capacity gradually transition to electric vehicles as economic and technological barriers recede, and political support for overcoming any remaining obstacles paves the way for an accelerated transition.
section_name: 2022).

section_content: A literature review was conducted to identify the conceptual and methodological status of the energy transition in transport, including energy, public policies, and technology and infrastructure needs. It was also possible to identify a series of barriers, such as charging infrastructure, battery management, the industry's favoritism toward conventional cars, the absence of policies to promote EV diffusion, the de ciency of availability at the dealership, including the limited variety of models to see or test drive, and a long waiting period for vehicle delivery once purchased and other determinants that have in uenced the energy transition process. Most of the authors who investigated these topics applied the literature review method since it provides a general framework of the state of the literature and allows knowing what type of research is currently being carried out. Likewise, different modeling techniques, surveys, and interviews were identi ed as predominant methodologies. Regarding the general theme, 64% have electric mobility as their central theme, 22% have other energy sources, and 14% have public policies. This allows us to assume that electric mobility is gaining more relevance and is denoted as a signi cant opportunity in the transport transition process. 

A series of conditions that mark the energy transition was detected; an example is a recharging infrastructure because it not only technically restricts the use of the vehicle but also generates insecurity for the buyer and users when migrating to other technologies. This is the reason why alternatives such as bidirectional (V2G) and unidirectional (V1G) intelligent charging infrastructure for unregulated household-level charging can be implemented. Another variable is the incentives, both tax and non-tax, this could fully promote the transition, as well as stop it; Incentives include tax reduction or exemption, vehicle cost reduction, and exclusive use areas for zero and low-emission vehicles. The de nition of public policies that bene t both the users of zero and low-emission vehicles and promote the energy transition is also relevant since governments must promote and guarantee this process, helping the various actors in the chain. 

Electric power stands out in this energy transition process as a zero-emission energy source. However, battery management from mineral extraction to nal waste disposal is a priority issue and could undermine the bene ts of electricity in transport. Research shows the rapid growth of electric vehicles and recognizes the need to identify potential barriers and incentives to promote these technologies. However, it is not trivial to identify such policies that will promote the promotion of electrical technologies. 

Additionally, for this alternative to be bene cial for the reduction of emissions, it is a priority that the source of electricity generation be through renewable energies, an issue that could take time to consolidate in all the countries of the world. On the other hand, biofuels are a quick alternative to achieve the transition; however, they are not enough to reduce emissions and meet the goals. 

The promotion of the energy transition in transport in developing countries must be accompanied by a series of public policies that facilitate and promote new technologies, considering the barriers, conditions, and opportunities of the population, given that this could stop or guarantee such a transition. 

During the review, a series of limitations were identi ed, which we will list below. Although several documents focused on energy transition in transport Worldwide were found, developed nations and European countries predominate in research on these issues. However, one of the most evident limitations when carrying out the literature review is the need for more articles and research focused on developing countries. For instance, just six documents about Latin America were evidenced in the literature review, one having Chile as its geographical scope, one in Brazil, and the other in Argentina, which shows that in addition to having little research or publications, it has a high research opportunity and could assuredly contribute signi cantly to policy de nitions. 

None of the documents focused on Latin American countries had the objective of presenting or evaluating energy transition policies, which means that the evaluation of actions has a limited scope and is probably neglecting measures that could signi cantly promote the energy transition in transport, particularly in developing countries such as Latin America. At the same time, a noticeable knowledge gap exists regarding the development of incentives, the formulation and assessment of policies, and the facilitation of collaboration among multidisciplinary stakeholders to integrate sustainability into the transport sector. As part of future research, it is proposed to introduce indicators for the assessment of sustainability in transport. 

On the other hand, the mode of transport that has received the most research is the road; due to the ease with which this mode of transport must migrate to other technologies. The different modes of transport, such as air, river, sea, and rail, have fewer published documents, which makes them limited modes in the investigation exercises.
section_name: Conclusions

section_content: Autor Consent for publication: All authors to publish the review paper. 

Competing interest: The authors declare that there is no con ict of nancial, professional, or personal interest to be declared. 

Funding: No funding was obtained for this study References Figures Geographical distribution of by continent or country
section_name: Declarations

section_content: Systematic literature review process Synthesis of the public policies implemented in different nations to promote the energy transition in transport.