How your legs can reduce your carbon footprint

04 Feb 2021

Cycling, e-biking and walking can help tackle the climate crisis – even if we swap the car for active travel just one day a week – according to our newly published study.

Many now believe that our ambitious carbon emission targets are unlikely to be met without a significant move away from motorised transport, and shifting to active travel could save as much as a quarter of personal CO2 emissions from transport.

Published in the journal Global Environmental Change, we believe this is the first international study of the carbon-reducing impact of city-based lifestyle changes. We reveal that increases in active mobility significantly lower carbon footprints, even in urban European contexts with a high incidence of walking and cycling.

The analysis comes as UK, and the world, enters the 2020s – what needs to be a ‘decade of action’, if global goals to limit rising temperatures are to be met. Ahead of this November’s COP26 UN climate summit in Glasgow, countries are expected to submit enhanced pledges to tackle emissions.

What does the study tell us?

Our study followed nearly 2,000 urban residents over time and found that those who switch just one trip per day from car driving to cycling reduced their carbon footprint by about 0.5 tonnes over a year, representing a substantial share of average per capita CO2 emissions. If just 10% of the population were to change travel behaviour in this way, the emissions savings would be around 4% of lifecycle CO2 emissions from all car travel.

To put this into context, for the cities in this study, average per capita CO2 emissions from transport (excl. international aviation and shipping) ranged between 1.8 tonnes of CO2 per person per year in the UK to 2.7 tonnes of CO2 per person per year in Austria. According to the Global Carbon Atlas, average per capita CO2 emissions from all activities were eight tonnes per year in the UK (on a consumption basis).

Addressing one of the ‘mobility myths’ head on – that active travel is mostly additional to motorised travel, not replacing it, thus more of it doesn’t mean lower emissions – we found empirical evidence that active travel indeed substitutes for motorised travel.

An increase in cycling, e-biking or walking over time independently lowered mobility-related lifecycle CO2 emissions in our study sample (see Figure below). And swapping the car for a bike or e-bike for just one day a week – or going from ‘not cycling’ to ‘cycling’ – drastically lowered mobility-related lifecycle CO2.

The findings suggest that, even if not all car trips could be substituted by bicycle trips, the potential for decreasing emissions is huge.

The largest benefits from shifts from car to active travel are for business travel, followed by social and leisure trips, and commuting to work or place of study. The finding that those who already cycled had 84% lower CO2 emissions from all daily travel than non-cyclists further shows the population benefits of travelling actively that already exist.

What did we do?

We – a group of transport, environment and health scientists from across Europe – collected primary data on daily travel behaviour, journey purpose, as well as personal and geospatial characteristics in seven European cities (Antwerp, Barcelona, London, Örebro, Rome, Vienna and Zürich) and derived mobility-related lifecycle CO2 emissions over time and space. ‘Lifecycle’ emissions included emissions at the point of use (pollution coming out of the tailpipe); emissions from energy supply of petrol, diesel, and electricity; and emissions from the manufacture, maintenance and recycling/disposal of vehicles and batteries. Statistical modelling of longitudinal panel data of 1,849 study participants was performed to assess how changes in active mobility, the ‘main mode’ of daily travel, and cycling frequency influenced changes in mobility-related lifecycle CO2 emissions.

What can we do as individuals – and as a society in a net zero world?

A typical response to the climate crisis is to ‘do more of something’, such as planting more trees or switching to electric vehicles. While these are important and effective in the long run, they are neither sufficient nor fast enough to meet our ambitious climate targets. Doing more of a good thing combined with doing less of a bad thing – and doing it now – is more compliant with a ‘net zero’ pathway and preserving our ‘perfect planet’ and our own futures.

Switching from car to active travel is one thing to do, which would make a real difference, and the scientists show how good this can be in cities. Not just for the climate but also for reducing social inequalities and improving public health and quality of urban life in a post-COVID-19 world.

Read the full paper here.