For years, the Transportation Energy Institute (TEI) has argued that simply replacing the world’s 1.5 billion combustion vehicles with new technology vehicles is an inefficient path to reducing transportation emissions. Achieving environmental objectives requires addressing the existing fleet while ensuring affordable and reliable access to energy for all users. TEI’s recent report, Driving Insight: A Five-Year Synthesis of Combustion Emissions Research, compiles findings from nine papers on this topic, identifying six consistent themes essential to achieving a sustainable transportation sector. The report emphasizes that sustainability must balance emissions reduction, affordability, and reliability.
A core finding of the synthesis is the importance of a life cycle perspective. Across all studies, life cycle analysis (LCA) showed that full emissions impacts must be considered to maximize environmental benefits at the lowest cost. Certain combinations of fuels and existing vehicle technologies can provide emissions reductions comparable to electric vehicles charged on a carbon-intensive grid. This underscores the need for data-driven assessments and a pragmatic, multi-faceted approach to decarbonization rather than relying on a single solution.
Technology diversity is another key insight. The reports highlight that emissions reduction strategies must match technologies to specific vehicle types and use cases, as no single solution works for all scenarios. Both combustion engine improvements and innovative fuel blends can play a role. A portfolio approach, tailored to operational demands and economic realities, is necessary to address the wide range of vehicles and transport modes effectively.
Policy alignment also emerged as critical. Government regulations, ESG expectations, and incentives influence business decisions, shaping the adoption of lower-emission technologies and fuels. Companies pursue emissions reductions not only for compliance but also to access capital, maintain market credibility, and achieve positive ROI. The interplay between public policy and corporate strategy drives significant shifts in technology adoption, energy production, and market behavior.
Addressing the existing vehicle fleet is essential, given that nearly 300 million internal combustion engine vehicles (ICEVs) are projected to remain on U.S. roads by 2035. TEI’s research suggests a dual-pronged approach: increasing the use of low-carbon intensity (CI) fuels and optimizing engine technologies to work efficiently with these fuels. Such strategies can deliver substantial near-term emissions reductions while the adoption of battery electric vehicles (BEVs) gradually grows over decades.
Scalability and infrastructure present additional challenges. Limitations in electric grids, fuel compatibility, land, feedstock availability, and supply chains all affect decarbonization efforts. TEI emphasizes that overcoming these constraints requires a diversified and adaptable strategy, integrating multiple technologies and fuels to accelerate emissions reductions across the existing fleet.
Affordability remains a persistent theme. Low-carbon solutions often cost more than traditional fuels, requiring policy support and incentives to promote adoption. Consumer behavior also plays a role: many vehicle buyers prefer familiar gasoline-powered or hybrid options, making low-CI fuels in ICEVs a pragmatic pathway to reduce emissions while maintaining convenience and reliability.
In conclusion, TEI’s synthesis shows that decarbonizing transportation is not a simple EV-versus-fuel debate. Effective strategies require a portfolio approach, blending policy, fuels, vehicle technologies, and infrastructure to suit diverse market conditions and fleet types. The studies collectively underscore that there is no single solution; achieving sustainability depends on integrating multiple interventions in a way that balances environmental impact, affordability, and reliability.
