From Our World in Data
Transport accounts for around one-quarter of global carbon dioxide (CO2) emissions from energy.1 In some countries — often richer countries with populations that travel often — transport can be one of the largest segments of an individual’s carbon footprint.
If you need to travel locally or abroad, what is the lowest-carbon way to do so?
In this chart, we see the comparison of travel modes by their carbon footprint. These are measured by the amount of greenhouse gases emitted per person to travel one kilometer.
These data come from the UK Government’s Department for Energy Security and Net Zero. They're the emission factors companies use to quantify and report their emissions. While the overall rankings of transport modes will probably be the same, there may be differences across countries based on their electricity mix, vehicle stock, and public transport network.
Greenhouse gases are measured in carbon dioxide equivalents (CO2eq), accounting for non-CO2 greenhouse gases and the increased warming effects of aviation emissions at high altitudes.2
Over short to medium distances, walking or cycling is nearly always the lowest carbon way to travel. While they’re not in the chart, the carbon footprint of cycling one kilometer is usually in the range of 16 to 50 grams CO2eq per km depending on how efficiently you cycle and what you eat.3
Using a bike instead of a car for short trips would reduce travel emissions by around 75%.
[Remember that the carbon dioxide we breathe out was originally extracted from the air by plants, so with walking or cycling, it's not a net addition to atmospheric CO2. But in the case of the meat we eat, there are also methane emissions to consider, and methane is 80 times as potent a greenhouse gas as CO2, and the plants don't breathe in methane.]
"National Rail" means all the railway companies except London Transport, and includes diesel and electrified routes. The reason Eurostar to Paris is so much lower is because France's electricity is mostly generated by nuclear.
For flights of less than 1000 km, the carbon intensity is very high, but falls as the flights lengthen, until about 3,500 km, after which it doesn't decline any further. Most carbon emissions from flying come from short-haul flights.
The lowest emissions per kilometre are in public transport, and if the grid was 100% renewable, and all public transport was 100% electric, emissions per kilometre would be much lower, coming only from emissions released during manufacture and construction.
E-buses presumably have much lower emissions than diesel buses.
Transport emissions are falling as EV sales take off, but to really cut emissions, we will need to deal with air travel. Electric planes are a start, but the biggest e-plane won't be going into service for at least another 2 years, and it won't (yet) be able to fly on intercontinental routes. In the meantime, use the train or bus or your EV.
Note also that this doesn't address emissions from shipping. Ironically, 40% of shipping emissions are from moving fossil fuels (coal, oil and LNG).
