Business travel emission factor trends

External decarbonisation trends for business travel activities — curated sources, uncertainty ranges, and pathway-ready projections.

• Global

  Decarbonisation of air travel — Global

  The UK’s business travel footprint shows that international air travel remains a small but highly emissions‑intensive portion of travel-related emissions. The 2016–2024 trend for the international first‑class flight emission factor moves from about 0.548 to a high near 0.562 in 2021–2022, before easing to around 0.539 in 2023–2024, indicating that fleet efficiency gains and shifts in premium travel demand have partially offset growth in emissions. BEIS/DEFRA’s GHG Conversion Factors for Company Reporting state that “emissions from air travel are calculated from fuel burn and occupancy and vary by seating class” (BEIS/DEFRA, GHG Conversion Factors for Company Reporting, 2024). ICAO also notes that “improvements in aircraft efficiency have not fully offset rising demand for international aviation” (ICAO, 2023). In the UK context, this trend is relevant across all regions and aligns with policy aims to decarbonise aviation while allowing necessary business mobility.

• Global

  Decarbonisation of diesel vehicle rental — Global

  The UK DESNZ historic data released in 2024 show a consistent downward path in emission factors from 2015 to 2024, with the figures moving from 0.185363 down toward 0.16983 across the period. This pattern aligns with broader decarbonization efforts in road transport, where fleet renewal toward newer, more efficient diesel models and a gradual shift to low-emission fleets are reducing per-kilometre emissions. As the IEA notes, “the transport sector continues to decarbonize as efficiency improves and electrification expands,” which supports observed reductions in emission factors. The official UK framework also underpins these calculations: BEIS/Department for Energy Security and Net Zero and related conversion factors provide the benchmarks used for estimating emissions from organizational activities, with downward revisions reflecting technological gains and policy-driven fleet changes. In 2025, the downward trend is likely to persist as rental fleets increasingly favor efficiency and alternative propulsion options.

• Global

  Decarbonisation of taxi travel — Global

  Across all regions, the emission factor for taxis has reduced over 2016–2024, with an overall roughly 9% reduction. This pattern mirrors broader shifts in business travel and taxi fleets: newer, more efficient engines, tighter urban emission rules, and greater use of cleaner fuels or hybrid configurations are replacing older, higher-emitting vehicles. According to DESNZ, this historic trend reflects steady efficiency gains and fleet renewal rather than short-term volatility. The trend is reinforced by global and national policy momentum toward lower transport emissions, including incentives for fleet modernization and the growing prevalence of low-emission zones; the ICCT notes that electrification and tighter standards are increasingly shaping taxi emissions, which supports the observed downward trajectory.

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