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How much CO2 do you save by taking the bus instead of driving? Compare per-passenger emissions for bus and car across different distances and countries.
A typical bus produces 68–90 g CO2 per passenger-km versus 170–271 g for a solo car driver — making buses 40–75% lower carbon. For a daily 20 km commute, switching from solo car to bus saves approximately 900–1,800 kg CO2 per year depending on the country.
18
kg CO2
90 g CO2/km
54
kg CO2
271 g CO2/km
The secret is occupancy. A diesel bus carries 40–60 passengers, meaning its total CO2 emissions per trip are divided among all those people. Even though a bus produces more emissions than a car in absolute terms per trip, the per-person figure plummets when the bus is full. The average bus occupancy in the UK is about 11 passengers (DEFRA), meaning each passenger sees just 1/11th of the bus's total emissions. As occupancy rises, the per-passenger carbon footprint falls further. Urban rush-hour routes with 40+ passengers can approach 20–30 g CO2/km per person — comparable to a bicycle with food calories factored in.
The average UK car carries just 1.55 people per trip. In the US, average occupancy is 1.5. This means most car journeys are essentially moving one person in a vehicle designed for five, at an effective emissions rate of 170–271 g CO2 per person per km — 3–5 times more carbon-intensive than a bus. The single biggest lever for reducing transport emissions at the personal level is either reducing car use or increasing vehicle occupancy through carpooling.
A fully-occupied car (4–5 passengers) sharing a journey can produce as little as 34–68 g CO2 per person per km — getting close to or below average bus emissions. This is why carpooling schemes are a legitimate carbon reduction strategy. However, for the vast majority of single-occupant or two-person journeys, the bus wins easily. Rural routes with low bus occupancy can narrow the gap, but for urban and suburban commuting, buses consistently outperform private cars.
Battery-electric buses paired with clean electricity grids bring per-passenger emissions down dramatically. In the UK, electric bus routes produce as little as 15–20 g CO2 per passenger-km — compared to 82 g for the average diesel bus. China currently operates over 420,000 electric buses (about 65% of its fleet), and cities like Shenzhen have gone 100% electric. As bus fleets electrify, the already large advantage over private cars will widen further — making the choice to take the bus even more impactful.
Covers practical follow-up questions readers often ask
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