Carbon Footprint of Transportation
Transport is the UK's largest source of CO₂ emissions, accounting for 27% of territorial greenhouse gas output. Understanding where transport emissions come from — and which choices reduce them most — is essential for anyone serious about their carbon footprint.
Transport emissions by mode: the full comparison
Not all transport is equal from a climate perspective. Here's how different modes compare on a per-passenger-kilometre basis:
| Mode | gCO₂e/km |
|---|---|
| ✈️ Short-haul flight (economy) | 255 |
| 🚗 Large petrol SUV | 225 |
| 🚗 Medium petrol car | 170 |
| 🚗 Medium diesel car | 150 |
| ✈️ Long-haul flight (incl. non-CO₂) | 195 |
| 🚌 Coach (National Express etc.) | 27 |
| 🚂 UK rail (average) | 41 |
| 🚌 Local bus | 79 |
| ⭐ Eurostar (London–Paris) | 4 |
| ⚡ Electric car (UK grid) | 43 |
| 🚲 E-bike | 8 |
| 🚶 Walking / cycling | 0 |
Source: DEFRA GHG Conversion Factors 2023. Flight figures include non-CO₂ radiative forcing.
Road transport: the dominant source
Cars and vans account for approximately 90% of UK road transport emissions. The UK has around 40 million licensed vehicles, and despite progress on EV uptake, the overwhelming majority still run on petrol or diesel.
Key facts about UK road transport emissions:
- Cars alone generate approximately 68 Mt CO₂ per year — about 16% of all UK emissions
- Vans (HGVs excluded) add another 20 Mt CO₂ per year
- The average UK car travels approximately 7,400 miles per year
- At 170 gCO₂/km, the average car trip emits 2 kg CO₂ per 10 km
SUV and 4x4 popularity has grown significantly — these vehicles emit 30–60% more CO₂ per km than medium family cars. The IEA estimates that the global shift toward larger vehicles has added 180 Mt CO₂/year compared to what would have been emitted if car size had stayed flat.
Aviation: high impact per journey
Aviation is responsible for approximately 8% of UK transport emissions by domestic accounting — but this figure understates the true climate impact, because:
- International aviation emissions are excluded from UK territorial accounting (they sit in a global "bunker fuels" category)
- Aircraft emit non-CO₂ pollutants at high altitude — contrails, water vapour, and nitrogen oxides — that roughly double the effective warming impact over a 20-year period
A single return economy flight from London to New York emits approximately 1.7 tonnes CO₂e per passenger (including non-CO₂ effects) — equivalent to 3–4 months of driving for an average UK driver.
The clearest action available for frequent flyers is to fly less, and to use trains where practical.
Rail: the clear winner for medium distances
UK rail emits approximately 41 gCO₂ per passenger-km — 76% less than a medium petrol car. Eurostar from London to Paris emits just 4 gCO₂/km — 97% less than flying the same route.
Rail's carbon advantage is powered by electrification and the UK's increasingly clean electricity grid. As more lines are electrified and the grid decarbonises, rail emissions will fall further automatically.
High-speed rail (HS2, TGV, ICE) generates slightly more emissions than slower trains per km (due to aerodynamic drag at speed) but still dramatically outperforms cars and flights on comparable routes.
Electric vehicles: the private car solution
If you need a car, switching to an electric vehicle is the single most impactful transport change available. An EV emits approximately 43 gCO₂/km on the UK grid — 75% less than a petrol equivalent. As the grid decarbonises further, EV emissions will fall automatically.
Read our full guide: Best Electric Cars UK 2025: Carbon Footprint Compared.
E-bikes and cycling: the overlooked solution
An e-bike emits approximately 8 gCO₂/km — 95% less than a petrol car. For urban journeys under 10 miles, e-bikes are faster than cars in traffic, cheaper to run, and have a negligible carbon footprint. E-bike ownership costs have fallen to £30–50/month all-in.
For commutes and local journeys, replacing even a few car trips per week with cycling or e-biking adds up to hundreds of kilograms of CO₂ saved per year.
Your personal transport footprint
Transport is one of the largest components of a personal carbon footprint. Use our free carbon footprint calculator to see exactly how your travel choices contribute to your total emissions — and explore which changes would make the biggest difference.
Frequently asked questions
What percentage of UK emissions comes from transport?
Transport accounts for approximately 27% of UK territorial greenhouse gas emissions — making it the largest single sector. Road transport (cars, vans, lorries) dominates, contributing around 90% of transport emissions. Aviation accounts for a further 8% of UK transport emissions.
What is the carbon footprint of driving a petrol car per km?
A typical medium petrol car emits approximately 170 gCO₂ per km in real-world driving. A large SUV or 4x4 emits around 210–270 gCO₂/km. By comparison, an electric car emits approximately 38–50 gCO₂/km on the UK grid.
Is the train or plane better for the environment?
Train travel is dramatically better for the environment. A UK train journey emits around 35–43 gCO₂ per passenger-km, while flying emits 130–250 gCO₂/km including non-CO₂ warming effects. For London–Edinburgh, the train emits approximately 90% less CO₂ than flying.
How can I reduce my transport carbon footprint?
The highest-impact actions are: switching from a petrol/diesel car to an EV (saves 1.5–2.5t CO₂/year), reducing flights (each long-haul return saves 1.5–3t), replacing car journeys with cycling, walking or public transport, and choosing trains over planes for European routes.
What is the carbon footprint of a long-haul flight?
A typical economy return flight from London to New York emits approximately 1.7 tonnes of CO₂ equivalent per passenger, including non-CO₂ warming effects from high-altitude emissions. A return flight to Australia from London emits approximately 3.8 tonnes per passenger.