Skip to main content

The transport hierarchy

In this article, Rob Harrison looks at what the transport hierarchy is, the climate impact of different forms of transport, and what actions consumers, companies and governments need to take to create a more sustainable transport system.

The notion of a 'green transport hierarchy' to help guide individual decisions as well as the planning decisions of public bodies has been around since at least the 1990s.

Traditionally, they would start with the best environmental option (walking) and end up with the worst (private cars). Public health bodies were also keen on this approach for obvious reasons.

Since the Covid19 pandemic, and some of the lessons learned during that period, it is now possible to see the hierarchy reimagined for the 2020s, such as the one below from the UK's Energy Saving Trust.

It is intriguing to consider that I am in some way 'travelling' when I am joining a Zoom video conference in Zaragosa – because it doesn't feel that way – but it is a useful additional idea to add into the conversation. (The impact of video communications can be found in our guide to video conferencing platforms.) Flying has also been included in this version because it is designed more as a guide for individuals rather than town planners.

Transport hierarchies provided a useful introduction to the notion of relative impacts of different modes of transport, but are, nowadays, being replaced by attempts to provide more sophisticated data on the wide variety of choices within each layer. For example, the next table down compares mode of transport and CO2e per mile: for the cycling figures it includes calories burned by the human pedalling, and so a transport hierarchy diagram would presumably list walking below cycling, since cycling is more energy efficient per mile.

Inverted pyramid of transport. From top: digital communications; walking and wheelchairs; cycling; public and shared transport; electric vehicles and car sharing; other vehicles; flying.
Transport hierarchy. Courtesy of Energy Saving Trust

Carbon literacy - understanding carbon impacts of different modes of transport

We have compiled the table below from data within the excellent book How Bad are Bananas? from long-time friend of Ethical Consumer, Mike Berners-Lee. A cornerstone for developing carbon literacy in the UK, the book explains how the calculations are made for each element, and how contested some of them still are. We are, after all, just at the beginning of understanding the real carbon impacts of everything we do.

The figures in the table mainly include an estimation of the embodied emissions of the vehicle and upkeep of the current infrastructure, but not building new infrastructure (e.g. new train lines). Nevertheless, by providing the best estimates we can, it can help us make the best decisions possible in what is a situation of some urgency.

In many ways, it is the surprising figures that give the most pause for thought. (Check out the cyclist eating cheeseburgers!)

We look in a bit more detail at the data on bikes and electric bikes in our guide on to bikes.

Mode of transport and CO2e per mile
Mode of transport CO2e per mile
Full 90-seater electric bus 6 g
Half-full London Routemaster (diesel hybrid) 46 g
Rural double decker with just you and the driver 2.5 kg
Conventional bike

40 g – powered by bananas

70 g – powered by cereal with cow’s milk

190 g – powered by bacon

310 g – powered by cheeseburgers (about the same emissions as driving)

Fully electric bike (with 50 g added for embodied carbon)

53 g – 12 mph no hills or stops

55 g – 12 mph with hills and stops

Underground tube train 68 g
Light rail or tram 72 g
Intercity train

80 g – second class

160 g – first class

Mid-size, 5-door electric car 180 g
Smart car doing a steady 60 mph 290 g
Average UK car doing 36 miles to the gallon 530 g
Range Rover Sport doing 90 mph 1.26 kg
Flying from London to Hong Kong return

3.5 tonnes – economy

4.5 tonnes – premium economy

10 tonnes – business class (twice a whole year’s 5-tonne personal budget)

13.9 tonnes – first class

Figures are from How Bad are Bananas?

What are the carbon emissions of travelling from London to Glasgow and back?

It is possible to use the same figures to calculate some of the relative impacts where a range of real-world options exists. This includes the embodied emissions of the vehicle, which are of less importance if you already have a car and are deciding how to make a single trip.

Many people travelled to Glasgow for the climate conference in November 2021. What do emissions look like for different modes of transport?

London to Glasgow return (a driving distance of c.424 miles)

  • Coach: 40 kg
  • Train: 64 kg
  • Small electric car, driver only: 148 kg
  • Small efficient petrol car, driver only: 237 kg
  • Economy class on plane: 368 kg
  • Large SUV, driver only: 1.02 tonnes
Pie chart showing carbon emissions of different modes of transport to go from London to Glasgow return: Coach 40kg Train 64kg Small electric car, driver only 148kg Small efficent petrol car, driver only 237kg Economy class on plane 368kg Large SUV, driver only 1.02 tonnes

Car ownership

76% of households have access to at least one car. Furthermore, the percentage of households with access to more than one car/van has increased from 8% to 35% since the early 1970s.

The cost of purchasing a motor vehicle is lower than 20 years ago, contributing to increased ownership. The Consumer Price Index shows that in 2018, the cost of purchasing a motor vehicle was 9% less than in 1998 in real terms.

Increased dependency on cars over time can be seen in the figures below, and in terms of distance to be travelled.

Changes in mode of transport over time

The figures below are useful to help inform public policy discussions. Because the Covid19 pandemic in 2020 and 2021 caused really sharp drops in travel, the most recent statistics aren't a reliable guide to our usual travel choices. We have therefore focused on data for the couple of years before 2020.

  • In 1952, people in the UK travelled 218 billion passenger kilometres a year and 30% of this distance was attributed to travel by private vehicle; by 2019, 86% of the 364 billion km travelled was attributed to travel by private vehicle.
  • The average distance travelled per person in Great Britain has increased from 4,400km per person in 1952 to 13,300km per person in 2019.
  • Between 1952 and 2019, the distance travelled by bus declined from 92 to 33 billion km, and by pedal cycle from 23 to 6 billion kilometres.
Bar chart showing percentage of journeys by trip length and main mode, for England in 2017. Figures in text.

More than consumer action is needed

Our 2021 Climate Gap Report was designed to place the need for consumer actions next to the need for co-ordinated actions from governments and companies too. The table below is an extract from the transport section of this report listing actions for each type of actor under the three key indicators we are choosing to track. Some feedback from readers on our Climate Gap Report suggested that perhaps we were focusing too much on the electrification of cars.

Because campaigning for change is at least as important as reducing individual footprints, we've also talked about this in some of our guides too. In the bicycles guide, for example, there is a section where we hear from our readers about what they've been doing to campaign for better cycling infrastructure in their local areas.

And in a feature in our bikes guide we hear from Sustrans on how important it is to 'design cities for tomorrow'.

Actions from the Climate Gap report
  Annual emissions from cars Annual emissions from aviation Electric car registrations
What does government need to do? Decarbonise electricity supply. Sense check road building. Support walking,
cycling and public transport.
Halt airport expansion. Frequent Flyer Levy. Encourage efficiency gains.
Aviation tax reform.
EV purchase subsidies. Support rapid rollout of charging infrastructure.
Mandatory zero-emission sales targets.
What do companies need to do? Sell more electric vehicles. Continue innovating on decarbonising HGVs. Reduce distance travelled. Replace business travel with online working. Increase plane efficiency. Develop sustainable aviation fuel.

Switch to electric cars and vans. Invest in charging infrastructure.

What do consumers need to do? Electrify. Reduce distance travelled. Switch to lower-carbon travel where
possible.
Reduce flying if possible. Replace cars with a fully electric vehicle as soon as possible.

Additional research by Ethical Consumer colleagues.