Travel · emission factor
The Carbon Footprint of Bus Travel
105 g CO₂e / km
Travelling by bus emits roughly 105 g CO₂e per passenger-kilometre, based on European Environment Agency and IPCC data. That is less than half the footprint of a petrol car carrying one person (231 g/km), making the bus one of the most accessible low-carbon options for everyday journeys — though still well above rail, cycling or walking.
Why a bus emits 105 g CO₂e per passenger-kilometre
A city or coach bus is a large diesel (increasingly hybrid or electric) vehicle that can burn 30–40 litres of fuel per 100 km — far more than a car. What makes it efficient is sharing: the vehicle's total emissions are divided among all passengers on board. The 105 g figure reflects typical average occupancy, often only a quarter to a third of seats filled across a full day of service. This is why occupancy is the single biggest lever: a full coach on a motorway can drop below 30 g per passenger-km, while a nearly empty urban bus at rush-hour-free times can rival a solo car ride. Stop-and-go city driving, idling at stops and lights, also pushes urban routes above long-distance coach averages.
How the bus compares with other transport
At 105 g CO₂e per passenger-km, the bus sits in the middle of the transport spectrum. It beats a solo petrol car (231 g) by more than half and a diesel car (192 g) by roughly 45%, and it is far below flying (255 g) or cruising (280 g). But rail on a low-carbon grid is around 20 g — five times cleaner — and an electric car on a clean grid is about 8 g, essentially just tire and brake wear. Cycling and walking are effectively zero. In practice, the bus is often the best available option where trains don't run: a 20 km daily commute by bus instead of a petrol car avoids roughly 2.5 kg of CO₂e per day, over half a tonne a year.
Electric and biogas buses are changing the picture
Transport accounts for about a quarter of the EU's greenhouse gas emissions, and road vehicles are the largest share, so bus fleets are a major decarbonisation target. Cities across Europe, China and North America are switching to battery-electric buses — China alone operates hundreds of thousands. An electric bus on a low-carbon grid can cut per-passenger emissions several-fold compared with diesel, and biogas or hybrid buses fall in between. The 105 g average will therefore fall over the coming decade as fleets turn over. For travellers today, the practical takeaway is that route and operator matter: a modern electric city bus or a well-filled intercity coach already performs far better than the average figure suggests.
How bus compares
g CO₂e / km · data as used in the Decarbonr app · sources: European Environment Agency, IPCC
How to reduce this footprint
- ✓ Choose intercity coaches over driving or short-haul flights — a full coach can emit under 30 g CO₂e per passenger-km.
- ✓ Where both exist, prefer the train: at around 20 g/km it is roughly five times cleaner than the average bus.
- ✓ Check whether your city runs electric or biogas buses on your route — their footprint is a fraction of diesel averages.
- ✓ Combine bus trips with walking or cycling for the first and last kilometre instead of a car ride to the stop.
Frequently asked questions
Is taking the bus better for the climate than driving?
Usually yes. A bus averages about 105 g CO₂e per passenger-km versus 231 g for a solo petrol car and 192 g for diesel. The advantage shrinks if the car carries several people, and a full electric car on a clean grid (around 8 g/km) beats the average bus.
Why isn't the bus as clean as the train?
Most buses still burn diesel and operate at partial occupancy, while trains carry hundreds of passengers and increasingly run on electricity. On a low-carbon grid, rail averages around 20 g CO₂e per passenger-km — about five times less than the 105 g bus average.
How much CO₂ does a daily bus commute produce?
A 10 km each-way commute (20 km/day) by bus emits about 2.1 kg CO₂e per day, or roughly 460 kg over a 220-day working year. The same commute in a solo petrol car would produce around 1 tonne — more than double.
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Sources & methodology: see Research & scientific references. Figures are averages used by the Decarbonr app; real-world values vary by production system, country, and occupancy.