Towards zero CO₂ emissions: Insights from EU vehicle on-board data

Transport tailpipe CO₂ emissions remain central to the EU's transport decarbonisation efforts. This study presents a data-driven methodology to assess Real-World (RW) CO₂ emissions based on On-Board Fuel and Energy Consumption Monitoring (OBFCM) data from 7.7 million passenger cars registered in the EU between 2021 and 2023. OBFCM data provide detailed insights into actual fuel consumption and CO₂ emissions, and the annual mileage, across different vehicle technologies. By analysing three years of OBFCM data, we identify RW-CO₂ emission patterns and variability driven by key technical, behavioural and geographical factors. Multivariable regression models yield emission factors for each powertrain/fuel type combination, enabling the estimation of total RW emissions for the entire fleet of newly registered vehicles per year. Vehicle mass and engine power are key drivers of RW CO₂ emissions variability for Internal Combustion Engine Vehicles (ICEVs) and Hybrid Electric Vehicles (HEVs), while electric driving share dominates for Plug-in Hybrid Electric Vehicles (PHEVs). Average in-use EU fleet emissions are estimated at 166 g/km for petrol and 170 g/km for diesel ICEVs; 149 g/km for petrol and 190 g/km for diesel HEVs; and 131 g/km and 150 g/km for petrol and diesel PHEVs, which show the highest CO₂ reduction potential. Annual RW emissions from newly registered vehicles in 2021 total 20.9 Mt., 18.7 Mt. for 2022 registrations and 20.5 Mt. in 2023, reflecting evolving fleet composition, fuel efficiency and annual distance. This methodology offers a robust empirical basis for quantifying RW CO₂ emissions and for monitoring the effectiveness of respective policy measures.