COVID-19 has likely caused the largest drop in transport emissions the world has ever seen. In a few months, however, we will all be getting back in our cars and planes in an attempt to return to normalcy. In this article, I’ll be telling you how to work out for yourself which modes of transport are the best for the environment. 

Under normal conditions we all need to get places, and that requires carbon emissions no matter how we do it. Even cycling or walking produces emissions by burning calories which you got from food, the production and transport of which produced emissions. How much carbon is produced by different modes of transport, however, varies considerably.

When you are evaluating how bad a mode of transport is for the environment, the first thing you want to look at is the fuel source. A car that runs on petrol, for instance, will produce significantly more emissions than an electric car which has been charged up on electricity from renewable sources like wind and solar. 

The second thing you want to look at is the weight of the vehicle divided by the number of passengers. Cars, for example, have a much higher impact than motorbikes, even if they run on the same fuel. That is because you are accelerating a tonne of metal to 120kph to get a 60kg person from point A to point B. That is unbelievably inefficient. The picture is a lot better if you have a full car, since the weight per passenger is 5 times less than if you were alone in the car. 

It is all about energy use. It takes much less energy to move a light object than a heavy one. It also takes a lot more energy to stop and start constantly while you are stuck in traffic than it does to cruise down an open road. Reducing the number of cars on the road is the best way to get rid of traffic, which would do wonders for both our emissions and air quality. 

Public transport is much better. Part of that is the reduction of traffic, but it is also down to the weight per passenger. While a bus is extremely heavy, it is still more efficient when you divide it by the number of people on board. 

The third thing you want to look at is how much carbon it took to produce the vehicle in the first place. This is known as the embodied emissions. Depending on the type of car and how much you drive it, the embodied emissions may account for as much as half of all the carbon released during the car’s lifetime. Often, then, it is better to run your old banger into the ground than to buy a new car, even if the new one is more efficient.


Adam Boland – Science Editor