John Eichberger |
January 2026
For years, the Transportation Energy Institute (TEI) has been saying that if the global objective is to reduce emissions from the transportation sector, relying on new technology vehicles to replace the 1.5 billion in operation around the world is an inefficient strategy that will fail to achieve established environmental objectives. It is absolutely essential to address the fleet of combustion vehicles in a way the preserves access to affordable and reliable transportation energy for all end users and all use cases. In fact, a significant portion of our published work the past five years has been focused on this topic – addressing the combustion engine fleet.
Recently, TEI published new report, Driving Insight: A Five-Year Synthesis of Combustion Emissions Research, a compilation and summary of the key learnings and insights derived from nine papers we published on this topic. These reports span hundreds of pages and include dozens of charts, graphs and data tables. A collective review of these papers identified six consistent themes that should guide all discussions about the future of combustion vehicles and liquid fuel markets if we are to indeed achieve a “sustainable” transportation sector. The combination of emissions reduction, affordability and reliability serves as a formula for reclaiming the definition of the word “sustainable,” because if vehicles or energy are not affordable and reliable whatever solution is being offered will fail.
Our review of these papers identified six key themes that will help guide discussions about this market and support its successful evolution to a truly sustainable transportation sector:
- Life Cycle Perspective —Life cycle analysis (LCA) served as a core analytic tool across these reports, which conclude that strategies must consider full life cycle emissions for maximum environmental benefit at the lowest cost. In fact, throughout the studies, LCAs found that different combinations of fuel options with existing vehicle technologies can deliver equivalent or superior emissions reductions than could be achieved from converting the fleet to electric vehicles (EVs) that are charged with electricity equal to the carbon intensity (CI) of the U.S. grid average at the time the reports were written. Insight like this can help focus attention on solutions that could yield the greatest benefit while delivering the lowest cost to consumers. The research encourages the use of a data-driven, life cycle–based assessment that acknowledges the varied impacts of different transportation energy sources and technologies, aiming for a pragmatic and multi-faceted approach to decarbonization rather than relying on a single, potentially insufficient, solution.
- Technology Diversity — Another consistent theme across these reports is the recognition that effective emissions reductions can be achieved by matching technologies with specific vehicle use cases. They emphasize that there is no single solution that can be applied to all scenarios, and that decarbonization solutions should be tailored to specific vehicle types and operational demands. Therefore, a portfolio approach is necessary because of the varied technical requirements, operational conditions, and economic considerations across different vehicle types and transport modes. No single solution fits all; a portfolio approach tailored to specific use cases is essential.
The reports discuss a wide array of decarbonization technologies and potential future opportunities, noting achieved progress and promising developments for both ICE improvements and combustion fuels innovation. Overall, the reports emphasize that successful decarbonization requires a nuanced approach that considers the specific needs and limitations of each vehicle type and operational context, and they promote the exploration of a diverse portfolio of technological and fuel-based solutions.
- Policy Alignment — While environmental, social, and governance (ESG) policies and funds have come under scrutiny, some of the foundational elements of the topic, especially the emissions component, remain relevant to corporate strategic planning. Whether the motivation is regulatory compliance, business-to-business relationships, access to affordable capital, or adherence to company values, the pursuit of achieving, tracking, and reporting lower emissions while generating a positive return on investment (ROI) continues to drive businesses throughout the world and there is a significant connection between these efforts and public policy.
The reports collectively illustrate a complex and evolving relationship between business motivations to reduce emissions, the resilience of environmental expectations and the influence of government policy. In essence, government policies create the framework and incentives that align business interests with broader environmental goals, while increased environmental expectations from investors and the public add pressure and motivation for companies to actively pursue emissions reductions. This dynamic interplay will continue to drive significant shifts in energy production, vehicle technology, and market strategies across the transportation sector and around the world. - Existing Fleet Solutions — With nearly 300 million ICEVs projected to remain on U.S. roads in 2035, ignoring the legacy fleet will significantly impede efforts to reduce transportation-related emissions. The reports suggest a multifaceted approach to reducing emissions from the existing fleet of vehicles, focusing heavily on advancements in both fuel composition and engine technology.
The primary strategy for fuel-related emissions reductions revolves around increasing the use of low-CI fuels and optimizing their blends within existing vehicle infrastructure. Meanwhile, engines can be optimized to work more efficiently with specific fuel properties. The reports suggest a dual-pronged approach: maximizing the use of low-carbon fuels in existing ICEVs and continuously improving ICE technology itself. This portfolio strategy aims to achieve substantial near-term GHG reductions while the number of BEVs in operation gradually increases over several decades. - Scalability and Infrastructure — Infrastructure challenges, ranging from electric grid limitations and fueling compatibility to land availability and feedstock volumes to supply chain difficulties, appear across nearly all reports. These bottlenecks affect market viability and are often decisive in scaling capabilities. The reports detail these various constraints affecting the decarbonization of the existing vehicle fleet.
Achieving significant emissions reductions from the existing fleet requires overcoming a complex web of interwoven constraints, and the reports emphasize that a diversified and adaptable strategy is essential to navigate these challenges and accelerate decarbonization. - Affordability — The reports provide a comprehensive overview of the economics of decarbonization options, addressing the financial implications for vehicle and fuel producers, distributors, retailers, and consumers. A recurring theme is that some low-carbon options are currently more expensive than their fossil-fuel counterparts, necessitating government policy support to bridge this cost gap and incentivize adoption. Understanding how costs affect various stakeholders is critical to determine successful deployment.
Yet, while cost analysis is important, consumer acceptance often is influenced by a range of factors other than cost and may be based upon perception, general preferences or even biases toward certain options. In addition, not all consumers are open to change when considering the vehicle they purchase. TEI found that fewer than 30% of consumers who said they might acquire a new vehicle within two years said they would consider something other than a gasoline-powered or hybrid vehicle. This resistance to change and the sheer ubiquity of gasoline stations makes ICEVs convenient for consumers and presents an opportunity to reduce emissions through the provision of low-CI fuels.
Conclusion
These reports collectively demonstrate that transportation decarbonization is not a binary electric vehicle-versus-fuel debate, but rather a layered combination of tradeoffs, timelines, technology, and consumer perceptions. While market and policy developments may have changed the landscape for some of these topics, the observations and conclusions presented in these studies were consistent with the conditions that prevailed when they were written. Further, the underlying concepts within each report have not significantly changed with time even as some of the associated details have evolved.
Thematic convergence across these independent studies, which were written by a variety of expert analysts, strengthens their collective argument for a pragmatic, portfolio-based decarbonization approach. An enduring lesson is that there is no single solution. Effective strategy blends policies, fuels, vehicles, and infrastructure in ways tailored to the market and diversity of the fleet.
