9. Let someone else drive: Why public transport is often the greenest way to get around

Public transport is often the greenest way to get around.  Here we look at the carbon intensity of travelling in different places around the world to see what makes transit green.

Public transportation is much more efficient than personal cars

Why is public transport often a very green way to travel? Public transport, in the form of trains and buses, tends to be much less carbon-intensive than car travel. In fact, in cases with very high occupancy, electrification of the system, and low-carbon electricity, public transport can often be even greener than cycling.

We’re going to compare the carbon intensity of a few public transport systems around the world to give you an idea of what makes very green transport possible. At 188 grams CO2 emitted per passenger kilometer travelled. The unit of choice is abbreviated to this: g CO2 e/pkm and accounts for the fact that public transport carries more than one passenger at a time. In short, London’s iconic black cab is pretty inefficient.

Old diesel engines are relatively low in terms of occupancy and the short stop-start trips make them inefficient. Local buses in the US score pretty poorly at 182 grams. This is because they’re very low in terms of occupancy and they’re mostly old, inefficient diesel engines. Local buses in the UK are better at 149 grams. This is mostly because they have higher occupancy rates. Heavy rail in the US is 116 grams. This is quite high for trains, mostly because they have quite low occupancy rates and they’re still predominantly powered by diesel engines.

At a hundred grams, London buses are considerably better than the national average, and that’s simply because they have much higher occupancy. At 81 grams, the London Underground is fantastic because it’s busy and it uses electricity pretty efficiently. Even though that electricity is carbon intensive.

The national rail in the UK does better at 67 grams because it’s mostly electrified and it does pretty well intended bus system. At 50 grams the New York metro is pretty green indeed that’s because it’s busy, reasonably efficient.

The average US school bus is surprisingly green because they have such high occupancy. Ferries are an incredibly energy efficient way to transport people, as we can see from the 23 gram figure. Japanese travel further by rail each year than any nationality on earth. Their high-speed rail system, the Shinkansen (新幹線 or しんかんせん), is very energy efficient and has extremely high occupancy, resulting in very low carbon emissions of 21 grams. People take the Shinkansen for every day purposes like short business trips, short vacations, even commuting.

The Eurostar is even better at 20 grams. Their trains might not be as efficient or as efficient as those using nuclear energy which is very low. Finally, at just 13 grams, the Norwegian rail network shows us that you don’t need to sacrifice.

This is my train into London. It’s fully electric has pretty high occupancy and thus is only about 50 grams. That means that I’m better off using it than driving the car unless I’ve got a car full of people – and its got to be pretty full like 3 or 4 passengers. Packing cars makes them more efficient and is a reason why we should car pool. I’ll catch you tomorrow for day ten when we talked about driving.

Back to the 30 day Shrink Guide: Introducing the Shrink

Lindsay Wilson
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I founded Shrink That Footprint in November 2012, after a long period of research. For many years I have calculated, studied and worked with carbon footprints, and Shrink That Footprint is that interest come to life.

I have an Economics degree from UCL, have previously worked as an energy efficiency analyst at BNEF and continue to work as a strategy consultant at Maneas.  I have consulted to numerous clients in energy and finance, as well as the World Economic Forum.

When I’m not crunching carbon footprints you’ll often find me helping my two year old son tend to the tomatoes, salad and peppers growing in our upcycled greenhouse.

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